Quantum random number generator
M. Stipcevic; B. Medved Rogina
2007-01-01
We report upon a novel principle for realization of a fast nondeterministic random number generator whose randomness relies on intrinsic randomness of the quantum physical processes of photonic emission in semiconductors and subsequent detection by the photoelectric effect. Timing information of detected photons is used to generate binary random digits-bits. The bit extraction method based on restartable clock theoretically eliminates both bias and autocorrelation while reaching efficiency of almost 0.5 bits per random event. A prototype has been built and statistically tested.
Computing Hypergraph Ramsey Numbers by Using Quantum Circuit
Ri Qu; Zong-shang Li; Juan Wang; Yan-ru Bao; Xiao-chun Cao
2012-10-12
Gaitan and Clark [Phys. Rev. Lett. 108, 010501 (2012)] have recently shown a quantum algorithm for the computation of the Ramsey numbers using adiabatic quantum evolution. We present a quantum algorithm to compute the two-color Ramsey numbers for r-uniform hypergraphs by using the quantum counting circuit.
Ramsey numbers and adiabatic quantum computing
Frank Gaitan; Lane Clark
2012-01-08
The graph-theoretic Ramsey numbers are notoriously difficult to calculate. In fact, for the two-color Ramsey numbers $R(m,n)$ with $m,n\\geq 3$, only nine are currently known. We present a quantum algorithm for the computation of the Ramsey numbers $R(m,n)$. We show how the computation of $R(m,n)$ can be mapped to a combinatorial optimization problem whose solution can be found using adiabatic quantum evolution. We numerically simulate this adiabatic quantum algorithm and show that it correctly determines the Ramsey numbers R(3,3) and R(2,s) for $5\\leq s\\leq 7$. We then discuss the algorithm's experimental implementation, and close by showing that Ramsey number computation belongs to the quantum complexity class QMA.
High speed optical quantum random number generation
Weinfurter, Harald
High speed optical quantum random number generation Martin F¨urst1,2,, Henning Weier1,2, Sebastian/publicationFile/30276/ais20 pdf.pdf (1999). 2. "Fips 140-2, security requirements for cryptographic modules
Quantum Statistical Testing of a Quantum Random Number Generator
Humble, Travis S
2014-01-01
The unobservable elements in a quantum technology, e.g., the quantum state, complicate system verification against promised behavior. Using model-based system engineering, we present methods for verifying the opera- tion of a prototypical quantum random number generator. We begin with the algorithmic design of the QRNG followed by the synthesis of its physical design requirements. We next discuss how quantum statistical testing can be used to verify device behavior as well as detect device bias. We conclude by highlighting how system design and verification methods must influence effort to certify future quantum technologies.
Hypergraph Ramsey Numbers and Adiabatic Quantum Algorithm
Ri Qu; Yan-ru Bao
2012-07-18
Gaitan and Clark [Phys. Rev. Lett. 108, 010501 (2012)] have recently presented a quantum algorithm for the computation of the Ramsey numbers R(m, n) using adiabatic quantum evolution. We consider that the two-color Ramsey numbers R(m, n; r) for r-uniform hypergraphs can be computed by using the similar ways in [Phys. Rev. Lett. 108, 010501 (2012)]. In this comment, we show how the computation of R(m, n; r) can be mapped to a combinatorial optimization problem whose solution be found using adiabatic quantum evolution.
Determine Ramsey numbers on a quantum computer
Hefeng Wang
2015-10-07
We present a quantum algorithm for computing the Ramsey numbers whose computational complexity grows super-exponentially with the number of vertices of a graph on a classical computer. The problem is mapped to a decision problem on a quantum computer, a probe qubit is coupled to a register that represents the problem and detects the energy levels of the problem Hamiltonian. The decision problem is solved by determining whether the probe qubit exhibits resonance dynamics. The algorithm shows a quadratic speedup over its classical counterparts, and the degenerate ground state problem in the adiabatic quantum evolution algorithm for this problem is avoided.
Swimming by numbers QUANTUM CONTROL
Mahadevan, L.
flow, providing key qualitative insight in fluid mechanics. For example, the so-called Reynolds number be described by a universal mechanical principle seems optimistic -- if not entirely unrealistic. Now, however and pressure forces relevant for net propulsion. A measure of the thrust force is given by the mass
Berns, Hans-Gerd
How To Order Complete part numbers for BD Series are shown on pages D-8 thru D-9. All switches supplied in "OFF" position. Specifications SWITCH FUNCTION: SPST - 1 thru 12 position available (except 11 position). CONTACT RATING: Carry: 100 mA max. @ 50 V DC. Switch: 100 mA max. @ 5 V DC or 25 mA max. @ 25 V
Fractal sets of dual topological quantum numbers
Wellington da Cruz
2004-06-18
The universality classes of the quantum Hall transitions are considered in terms of fractal sets of dual topological quantum numbers filling factors, labelled by a fractal or Hausdorff dimension defined into the interval $1 < h < 2$ and associated with fractal curves. We show that our approach to the fractional quantum Hall effect-FQHE is free of any empirical formula and this characteristic appears as a crucial insight for our understanding of the FQHE. According to our formulation, the FQHE gets a fractal structure from the connection between the filling factors and the Hausdoff dimension of the quantum paths of particles termed fractons which obey a fractal distribution function associated with a fractal von Neumann entropy. This way, the quantum Hall transitions satisfy some properties related to the Farey sequences of rational numbers and so our theoretical description of the FQHE establishes a connection between physics, fractal geometry and number theory. The FQHE as a convenient physical system for a possible prove of the Riemann hypothesis is suggested.
True random numbers from amplified quantum vacuum
M. Jofre; M. Curty; F. Steinlechner; G. Anzolin; J. P. Torres; M. W. Mitchell; V. Pruneri
2011-10-17
Random numbers are essential for applications ranging from secure communications to numerical simulation and quantitative finance. Algorithms can rapidly produce pseudo-random outcomes, series of numbers that mimic most properties of true random numbers while quantum random number generators (QRNGs) exploit intrinsic quantum randomness to produce true random numbers. Single-photon QRNGs are conceptually simple but produce few random bits per detection. In contrast, vacuum fluctuations are a vast resource for QRNGs: they are broad-band and thus can encode many random bits per second. Direct recording of vacuum fluctuations is possible, but requires shot-noise-limited detectors, at the cost of bandwidth. We demonstrate efficient conversion of vacuum fluctuations to true random bits using optical amplification of vacuum and interferometry. Using commercially-available optical components we demonstrate a QRNG at a bit rate of 1.11 Gbps. The proposed scheme has the potential to be extended to 10 Gbps and even up to 100 Gbps by taking advantage of high speed modulation sources and detectors for optical fiber telecommunication devices.
Stern-Gerlach Experiments and Complex Numbers in Quantum Physics
S. Sivakumar
2012-07-09
It is often stated that complex numbers are essential in quantum theory. In this article, the need for complex numbers in quantum theory is motivated using the results of tandem Stern-Gerlach experiments
L^2-Betti numbers of coamenable quantum groups
Kyed, David
2007-01-01
We study the relationship between the notion of coamenability of a compact quantum group and the notion of amenability of its fusion algebra. We furthermore propose a Foelner condition for compact quantum groups. Using this we prove that for a coamenable compact matrix quantum group with tracial Haar state, the enveloping von Neumann algebra is dimension flat over the Hopf *-algebra of matrix coefficients. This generalizes a theorem of Lueck from the group case to the quantum group case, and provides examples of compact quantum groups with vanishing L^2-Betti numbers.
Harmonic resolution as a holographic quantum number
Bousso, Raphael
2009-01-01
LBNL- 57239 Harmonic resolution as a holographic quantumhep-th/0310223 UCB-PTH-03/26 Harmonic resolution as aquantum number, the harmonic resolution K. The Bekenstein
Iyengar, Srinivasan S.
Quantum Mechanics Course Number: C668 C668: Special topics in physical chemistry: Advanced Quantum Mechanics Instructor: Srinivasan S. Iyengar Office Hours Wednesday, Friday 10:30AM-12PM (Chemistry C202B@gmail.com Chemistry, Indiana University i c 2014, Srinivasan S. Iyengar (instructor) #12;Quantum Mechanics Course
SAMQUA - Quantum Numbers of Compound Nuclear States for R-Matrix...
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Is there quantum chaos in the prime numbers?
Todd Timberlake; Jeffery Tucker
2008-01-07
A statistical analysis of the prime numbers indicates possible traces of quantum chaos. We have computed the nearest neighbor spacing distribution, number variance, skewness, and excess for sequences of the first N primes for various values of N. All four statistical measures clearly show a transition from random matrix statistics at small N toward Poisson statistics at large N. In addition, the number variance saturates at large lengths as is common for eigenvalue sequences. This data can be given a physical interpretation if the primes are thought of as eigenvalues of a quantum system whose classical dynamics is chaotic at low energy but regular at high energy. We discuss some difficulties with this interpretation in an attempt to clarify what kind of physical system might have the primes as its quantum eigenvalues.
Maximization of Extractable Randomness in a Quantum Random-Number Generator
J. Y. Haw; S. M. Assad; A. M. Lance; N. H. Y. Ng; V. Sharma; P. K. Lam; T. Symul
2015-05-19
The generation of random numbers via quantum processes is an efficient and reliable method to obtain true indeterministic random numbers that are of vital importance to cryptographic communication and large-scale computer modeling. However, in realistic scenarios, the raw output of a quantum random-number generator is inevitably tainted by classical technical noise. The integrity of the device can be compromised if this noise is tampered with, or even controlled by some malicious party. To safeguard against this, we propose and experimentally demonstrate an approach that produces side-information independent randomness that is quantified by min-entropy conditioned on this classical noise. We present a method for maximizing the conditional min-entropy of the number sequence generated from a given quantum-to-classical-noise ratio. The detected photocurrent in our experiment is shown to have a real-time random-number generation rate of 14 (Mbit/s)/MHz. The spectral response of the detection system shows the potential to deliver more than 70 Gbit/s of random numbers in our experimental setup.
On the dual topological quantum numbers filling factors
Wellington da Cruz
2003-05-26
We consider recent experimental results [W. Pan {\\it et al}, Phys. Rev. Lett. {\\bf 90}, 016801 (2003)] for occurrence of the fractional quantum Hall effect-FQHE under the perspective of our formulation in terms of {\\it fractons}. These objects carry rational or irrational values of spin and satisfy a {\\it fractal distribution function} associated with a {\\it fractal von Neumann entropy}. According to our approach the {\\it FQHE occurs in pairs of dual topological quantum numbers fillings factors} and this geometrical character comes from the {\\it connection betwenn the fractal parameter or Hausdorff dimension $h$ and the spin $s$ of the particles}. We suggest to the experimentalists consider our ideas and verify in fact that this phenomenon of FQHE satisfy a {\\it symmetry principle} discovered by us, i.e, {\\it the duality symmetry betwenn universal classes of fractons}.
A self-testing quantum random number generator
Tommaso Lunghi; Jonatan Bohr Brask; Charles Ci Wen Lim; Quentin Lavigne; Joseph Bowles; Anthony Martin; Hugo Zbinden; Nicolas Brunner
2014-10-10
A central issue in randomness generation is to estimate the entropy of the output data generated by a given device. Here we present a protocol for self-testing quantum random number generation, in which the entropy of the raw data can be monitored in real-time. In turn, this allows the user to adapt the randomness extraction procedure, in order to continuously generate high quality random bits. Using a fully optical implementation, we demonstrate that our protocol is practical and efficient, and illustrate its self-testing capacity.
Robust quantum random number generator based on avalanche photodiodes
Fang-Xiang Wang; Chao Wang; Wei Chen; Shuang Wang; Fu-Sheng Lv; De-Yong He; Zhen-Qiang Yin; Hong-Wei Li; Guang-Can Guo; Zheng-Fu Han
2015-06-18
We propose and demonstrate a scheme to realize a high-efficiency truly quantum random number generator (RNG) at room temperature (RT). Using an effective extractor with simple time bin encoding method, the avalanche pulses of avalanche photodiode (APD) are converted into high-quality random numbers (RNs) that are robust to slow varying noise such as fluctuations of pulse intensity and temperature. A light source is compatible but not necessary in this scheme. Therefor the robustness of the system is effective enhanced. The random bits generation rate of this proof-of-principle system is 0.69 Mbps with double APDs and 0.34 Mbps with single APD. The results indicate that a high-speed RNG chip based on the scheme is potentially available with an integrable APD array.
Quantum chaos for exact and broken K quantum number in the interacting-boson model
Paar, V.; Vorkapic, D. (Prirodoslovno-matematicki fakultet, University of Zagreb, 41000 Zagreb, Yugoslavia (YU))
1990-05-01
We show that the exact {ital K} quantum number in the SU(3) limit of the interacting-boson model has a strong effect on the fluctuation properties: Pure sequences of a single {ital K} value have {Delta}{sub 3} statistic close to the Gaussian overlap ensemble prediction while mixed sequences with combined {ital K} values are removed far from the Gaussian overlap ensemble because of {ital K} degeneracy, exceeding even the Poisson-ensemble prediction. Applying the extended interacting boson model to the realistic case of {sup 164}Er nucleus, we have demonstrated that weak breaking of the {ital K} quantum number introduces a very rapid change in fluctuation properties towards those of a pure sequence.
Atomic and Molecular Quantum Theory Course Number: C561 26 Group Theory Basics
Iyengar, Srinivasan S.
Atomic and Molecular Quantum Theory Course Number: C561 26 Group Theory Basics 1. Reference: "Group Theory and Quantum Mechanics" by Michael Tinkham. 2. We said earlier that we will go looking for the set, Indiana University 266 c 2003, Srinivasan S. Iyengar (instructor) #12;Atomic and Molecular Quantum Theory
Low-bias high-speed quantum random number generator via shaped optical pulses
Kwiat, Paul
Low-bias high-speed quantum random number generator via shaped optical pulses Michael A. Wayne generator (QRNG) based on the digitized time interval between random photon arrivals. By tailoring, secure quantum random number generation at rates exceeding 110 Mbit/s. ©2010 Optical Society of America
Local Availability of mathematics and number scaling: Effects on quantum physics
Paul Benioff
2012-05-01
Local availability of mathematics and number scaling provide an approach to a coherent theory of physics and mathematics. Local availability of mathematics assigns separate mathematical universes, U_{x}, to each space time point, x. The mathematics available to an observer, O_{x}, at x is contained in U_{x}. Number scaling is based on extending the choice freedom of vector space bases in gauge theories to choice freedom of underlying number systems. Scaling arises in the description, in U_{x}, of mathematical systems in U_{y}. If a_{y} or \\psi_{y} is a number or a quantum state in U_{y}, then the corresponding number or state in U_{x} is r_{y,x}a_{x} or r_{y,x}\\psi_{x}. Here a_{x} and \\psi_{x} are the same number and state in U_{x} as a_{y} and \\psi_{y} are in U_{y}. If y=x+\\hat{\\mu}dx is a neighbor point of x, then the scaling factor is r_{y,x}=\\exp(\\vec{A}(x)\\cdot\\hat{\\mu}dx) where \\vec{A} is a vector field, assumed here to be the gradient of a scalar field. The effects of scaling and local availability of mathematics on quantum theory show that scaling has two components, external and internal. External scaling is shown above for a_{y} and \\psi_{y}. Internal scaling occurs in expressions with integrals or derivatives over space or space time. An example is the replacement of the position expectation value, \\int\\psi^{*}(y)y\\psi(y)dy, by \\int_{x}r_{y,x}\\psi^{*}_{x}(y_{x})y_{x}\\psi_{x}(y_{x})dy_{x}. This is an integral in U_{x}. The good agreement between quantum theory and experiment shows that scaling is negligible in a space region, L, in which experiments and calculations can be done, and results compared. L includes the solar system, but the speed of light limits the size of L to a few light years. Outside of $L$, at cosmological distances, the limits on scaling are not present.
Iyengar, Srinivasan S.
"niche" area called quantum dots. 1. A quantum dot is a very small chunk of semiconductor material with quantum-like properties. These are any effects that the bulk form of the same material does not possess quantum mechanical proper- ties and discrete energy levels. 3. As a first approximation these materials
Joao Batista Rosa Silva; Rubens Viana Ramos
2006-07-26
Aiming the construction of quantum computers and quantum communication systems based on optical devices, in this work we present possible implementations of quantum and classical CNOTs gates, as well an optical setup for generation and distribution of bipartite entangled states, using linear optical devices and photon number quantum non-demolition measurement.
Nearest neighbor spacing distribution of prime numbers and quantum chaos
Marek Wolf
2014-01-07
We give heuristic arguments and computer results to support the hypothesis that, after appropriate rescaling, the statistics of spacings between adjacent prime numbers follows the Poisson distribution. The scaling transformation removes the oscillations in the NNSD of primes. These oscillations have the very profound period of length six. We also calculate the spectral rigidity $\\Delta_3$ for prime numbers by two methods. After suitable averaging one of these methods gives the Poisson dependence $\\Delta_3(L)=L/15$.
Nonradiative recombination --critical in choosing quantum well number for InGaN/GaN
Demir, Hilmi Volkan
results indicate that, though the efficiency droop is suppressed, the LED optical power is first improved-emitting diodes (LEDs) possessing varied quantum well (QW) numbers were systematically investigated both guidelines on choosing the critical QW number when designing LED structures. ©2014 Optical Society of America
Level repulsion, nuclear chaos, and conserved quantum numbers
Garrett, J.D.
1993-12-01
A statistical analysis of the distribution of level spacings for states with the same spin and parity is described in which the average spacing is calculated for the total ensemble. Though the resulting distribution of level spacings for states of deformed nuclei with Z = 62 - 75 and A = 155 - 185 is the closest to that of a Poisson distribution yet obtained for nuclear levels, significant deviations are observed for small level spacings. Many, but not all, of the very closely-spaced levels have K-values differing by several units. The analysis of level spacings in {sup 157}Ho indicate that considerable caution should be excerised when drawing conclusions from such an analysis for a single deformed nucleus, since the sizable number of spacings that can be obtained from a few rotational bands are not all independent.
Adam Miranowicz; Sahin K. Ozdemir; Jiri Bajer; Go Yusa; Nobuyuki Imoto; Yoshiro Hirayama; Franco Nori
2014-10-09
We discuss methods of quantum state tomography for solid-state systems with a large nuclear spin $I=3/2$ in nanometer-scale semiconductors devices based on a quantum well. Due to quadrupolar interactions, the Zeeman levels of these nuclear-spin devices become nonequidistant, forming a controllable four-level quantum system (known as quartit or ququart). The occupation of these levels can be selectively and coherently manipulated by multiphoton transitions using the techniques of nuclear magnetic resonance (NMR) [Yusa et al., Nature (London) 434, 101 (2005)]. These methods are based on an unconventional approach to NMR, where the longitudinal magnetization $M_z$ is directly measured. This is in contrast to the standard NMR experiments and tomographic methods, where the transverse magnetization $M_{xy}$ is detected. The robustness against errors in the measured data is analyzed by using condition numbers. We propose several methods with optimized sets of rotations. The optimization is applied to decrease the number of NMR readouts and to improve the robustness against errors, as quantified by condition numbers. An example of state reconstruction, using Monte Carlo methods, is presented. Tomographic methods for quadrupolar nuclei with higher-spin numbers (including $I=7/2$) are also described.
Multi-bit quantum random number generation by measuring positions of arrival photons
Yan, Qiurong; Zhao, Baosheng; Liao, Qinghong; Zhou, Nanrun
2014-10-15
We report upon the realization of a novel multi-bit optical quantum random number generator by continuously measuring the arrival positions of photon emitted from a LED using MCP-based WSA photon counting imaging detector. A spatial encoding method is proposed to extract multi-bits random number from the position coordinates of each detected photon. The randomness of bits sequence relies on the intrinsic randomness of the quantum physical processes of photonic emission and subsequent photoelectric conversion. A prototype has been built and the random bit generation rate could reach 8 Mbit/s, with random bit generation efficiency of 16 bits per detected photon. FPGA implementation of Huffman coding is proposed to reduce the bias of raw extracted random bits. The random numbers passed all tests for physical random number generator.
Stark broadening of high principal quantum number hydrogen Balmer lines in low-density laboratory an electron density di- agnostic, e.g., for tokamak edge plasmas 13 and other magnetic fusion energy MFE show a very good agreement. Density and temperature dependences of the linewidths, as well as relative
Attacks exploiting deviation of mean photon number in quantum key distribution and coin tossing
Shihan Sajeed; Igor Radchenko; Sarah Kaiser; Jean-Philippe Bourgoin; Anna Pappa; Laurent Monat; Matthieu Legre; Vadim Makarov
2015-03-30
The security of quantum communication using a weak coherent source requires an accurate knowledge of the source's mean photon number. Finite calibration precision or an active manipulation by an attacker may cause the actual emitted photon number to deviate from the known value. We model effects of this deviation on the security of three quantum communication protocols: the Bennett-Brassard 1984 (BB84) quantum key distribution (QKD) protocol without decoy states, Scarani-Acin-Ribordy-Gisin 2004 (SARG04) QKD protocol, and a coin-tossing protocol. For QKD, we model both a strong attack using technology possible in principle, and a realistic attack bounded by today's technology. To maintain the mean photon number in two-way systems, such as plug-and-play and relativistic quantum cryptography schemes, bright pulse energy incoming from the communication channel must be monitored. Implementation of a monitoring detector has largely been ignored so far, except for ID Quantique's commercial QKD system Clavis2. We scrutinize this implementation for security problems, and show that designing a hack-proof pulse-energy-measuring detector is far from trivial. Indeed the first implementation has three serious flaws confirmed experimentally, each of which may be exploited in a cleverly constructed Trojan-horse attack. We discuss requirements for a loophole-free implementation of the monitoring detector.
Quantum Chaos & Quantum Computers
D. L. Shepelyansky
2000-06-15
The standard generic quantum computer model is studied analytically and numerically and the border for emergence of quantum chaos, induced by imperfections and residual inter-qubit couplings, is determined. This phenomenon appears in an isolated quantum computer without any external decoherence. The onset of quantum chaos leads to quantum computer hardware melting, strong quantum entropy growth and destruction of computer operability. The time scales for development of quantum chaos and ergodicity are determined. In spite the fact that this phenomenon is rather dangerous for quantum computing it is shown that the quantum chaos border for inter-qubit coupling is exponentially larger than the energy level spacing between quantum computer eigenstates and drops only linearly with the number of qubits n. As a result the ideal multi-qubit structure of the computer remains rather robust against imperfections. This opens a broad parameter region for a possible realization of quantum computer. The obtained results are related to the recent studies of quantum chaos in such many-body systems as nuclei, complex atoms and molecules, finite Fermi systems and quantum spin glass shards which are also reviewed in the paper.
Nie, You-Qi; Zhang, Jun Pan, Jian-Wei; Zhang, Hong-Fei; Wang, Jian; Zhang, Zhen; Ma, Xiongfeng
2014-02-03
We present a practical high-speed quantum random number generator, where the timing of single-photon detection relative to an external time reference is measured as the raw data. The bias of the raw data can be substantially reduced compared with the previous realizations. The raw random bit rate of our generator can reach 109 Mbps. We develop a model for the generator and evaluate the min-entropy of the raw data. Toeplitz matrix hashing is applied for randomness extraction, after which the final random bits are able to pass the standard randomness tests.
Shepelyansky, Dima
of Quantum Chaos and Imperfection Effects Pil Hun Song1 and Dima L. Shepelyansky2 1 Max-Planck-Institut fÃ¼r model in the regime of quantum chaos. It is shown that there are two types of physical characteristics of imperfection effects we analyze in this paper their influence on a quantum compu- tation of quantum chaos
Suzuki, Kosuke Takubo, Shota; Kato, Tadashi; Yamazoe, Masatoshi; Hoshi, Kazushi; Sakurai, Hiroshi; Homma, Yoshiya; Itou, Masayoshi; Sakurai, Yoshiharu
2014-08-18
A spin specific magnetic hysteresis (SSMH) curve and an orbital specific magnetic hysteresis (OSMH) curve are obtained for Fe/Au/Fe/MgO multilayers by magnetic Compton scattering and SQUID magnetometer measurements. The SSMH curve with each contribution of magnetic quantum number |m|?=?0, 1, and 2 states is obtained by decomposition analyses of magnetic Compton profiles. Residual magnetization is observed for the SSMH curve with magnetic quantum number |m|?=?0, 2 and the OSMH curve. Although the SQUID magnetometer measurements do not show perpendicular magnetic anisotropy (PMA) in the present Fe/Au/Fe/MgO multilayer film, the SSMH curve with magnetic quantum number |m|?=?0, 2 and OSMH curve show switching behaviors of PMA.
Fluctuations of the number of particles within a given volume in cold quantum gases
Astrakharchik, G. E.; Combescot, R.; Pitaevskii, L. P.
2007-12-15
In ultracold gases many experiments use atom imaging as a basic observable. The resulting image is averaged over a number of realizations and mostly only this average is used. Only recently the noise has been measured to extract physical information. In the present paper we investigate the quantum noise arising in these gases at zero temperature. We restrict ourselves to the homogeneous situation and study the fluctuations in particle number found within a given volume in the gas, and more specifically inside a sphere of radius R. We show that zero-temperature fluctuations are not extensive and the leading term scales with sphere radius R as R{sup 2} ln R (or ln R) in three- (or one-) dimensional systems. We calculate systematically the next term beyond this leading order. We consider first the generic case of a compressible superfluid. Then we investigate the whole Bose-Einstein-condensation (BEC) -BCS crossover, and in particular the limiting cases of the weakly interacting Bose gas and of the free Fermi gas.
An On-Demand Optical Quantum Random Number Generator with In-Future Action and Ultra-Fast Response
Mario Stip?evi?; Rupert Ursin
2015-06-09
Random numbers are essential for our modern information based society e.g. in cryptography. Unlike frequently used pseudo-random generators, physical random number generators do not depend on complex algorithms but rather on a physical process to provide true randomness. Quantum random number generators (QRNG) do rely on a process, which can be described by a probabilistic theory only, even in principle. Here we present a conceptually simple implementation, which offers a 100% efficiency of producing a random bit upon a request and simultaneously exhibits an ultra low latency. A careful technical and statistical analysis demonstrates its robustness against imperfections of the actual implemented technology and enables to quickly estimate randomness of very long sequences. Generated random numbers pass standard statistical tests without any post-processing. The setup described, as well as the theory presented here, demonstrate the maturity and overall understanding of the technology.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Benioff, Paul
2009-01-01
This work is based on the field of reference frames based on quantum representations of real and complex numbers described in other work. Here frame domains are expanded to include space and time lattices. Strings of qukits are described as hybrid systems as they are both mathematical and physical systems. As mathematical systems they represent numbers. As physical systems in each frame the strings have a discrete Schrodinger dynamics on the lattices. The frame field has an iterative structure such that the contents of a stagejframe have images in a stagej-1(parent) frame. A discussion of parent frame images includes themore »proposal that points of stagejframe lattices have images as hybrid systems in parent frames. The resulting association of energy with images of lattice point locations, as hybrid systems states, is discussed. Representations and images of other physical systems in the different frames are also described.« less
Emile Okada; Richard Tanburn; Nikesh S. Dattani
2015-08-28
Quantum annealing has recently been used to determine the Ramsey numbers R(m,2) for 3 Ramsey number Hamiltonians used were tremendously smaller than the full 128-qubit capacity of the device used. The reason these auxiliary qubits were needed was because the best quantum annealing devices at the time (and still now) cannot implement multi-qubit interactions beyond 2-qubit interactions, and they are also limited in their capacity for 2-qubit interactions. We present a method which allows the full qubit capacity of a quantum annealing device to be used, by reducing multi-qubit and 2-qubit interactions. With our method, the device used in the 2013 Ramsey number quantum computation could have determined R(16,2) and R(4,3) with under 10 minutes of runtime.
New results for the missing quantum numbers labeling the quadrupole and octupole boson basis
A. Gheorghe; A. A. Raduta
2004-10-27
The many $2^k$-pole boson states, $|N_kv_k\\alpha_k I_kM_k>$ with $k=2,3$, realize the irreducible representation (IR) for the group reduction chains $SU(2k+1)\\supset R_{2k+1}\\supset R_3\\supset R_2$. They have been analytically studied and widely used for the description of nuclear systems. However, no analytical expression for the degeneracy $d_v(I)$ of the $R_{2k+1}$'s IR, determined by the reduction $R_{2k+1}\\supset R_3$, is available. Thus, the number of distinct values taken by $\\alpha_k$ has been so far obtained by solving some complex equations. Here we derive analytical expressions for the degeneracy $d_v(I)$ characterizing the octupole and quadrupole boson states, respectively. The merit of this work consists of the fact that it completes the analytical expressions for the $2^k$-pole boson basis.
Iyengar, Srinivasan S.
of obtaining these measurements is basically a dot product. The dot product can also be interpreted as a proAtomic and Molecular Quantum Theory Course Number: C561 C A Measurement is a Projection or a "dot" product (or inner product)!! 1. Lets go back and consider the Stern Gerlach experiment that we studied
Shepelyansky, Dima
of Quantum Chaos in Finite Interacting Fermi Systems Ph. Jacquod1 and D. L. Shepelyansky2, * 1 Institut de quantum chaos and thermalization set in. [S0031-9007(97)03971-9] PACS numbers: 05.45.+b, 05.30.Fk, 24 of them, we can quote models of quantum chaos, where RMT appears due to the classically chaotic
VOLUME 82, NUMBER 21 P H Y S I C A L R E V I E W L E T T E R S 24 MAY 1999 Quantum Chaos of Science and Technology of China, Hefei, China (Received 26 October 1998) We study quantum chaos in a non.65.Sq In the study of quantum chaos, most works have been concentrated on quantum systems whose
Finite groups and quantum physics
Kornyak, V. V.
2013-02-15
Concepts of quantum theory are considered from the constructive 'finite' point of view. The introduction of a continuum or other actual infinities in physics destroys constructiveness without any need for them in describing empirical observations. It is shown that quantum behavior is a natural consequence of symmetries of dynamical systems. The underlying reason is that it is impossible in principle to trace the identity of indistinguishable objects in their evolution-only information about invariant statements and values concerning such objects is available. General mathematical arguments indicate that any quantum dynamics is reducible to a sequence of permutations. Quantum phenomena, such as interference, arise in invariant subspaces of permutation representations of the symmetry group of a dynamical system. Observable quantities can be expressed in terms of permutation invariants. It is shown that nonconstructive number systems, such as complex numbers, are not needed for describing quantum phenomena. It is sufficient to employ cyclotomic numbers-a minimal extension of natural numbers that is appropriate for quantum mechanics. The use of finite groups in physics, which underlies the present approach, has an additional motivation. Numerous experiments and observations in the particle physics suggest the importance of finite groups of relatively small orders in some fundamental processes. The origin of these groups is unclear within the currently accepted theories-in particular, within the Standard Model.
Quantum Chaos and Quantum Algorithms
Daniel Braun
2001-10-05
It was recently shown (quant-ph/9909074) that parasitic random interactions between the qubits in a quantum computer can induce quantum chaos and put into question the operability of a quantum computer. In this work I investigate whether already the interactions between the qubits introduced with the intention to operate the quantum computer may lead to quantum chaos. The analysis focuses on two well--known quantum algorithms, namely Grover's search algorithm and the quantum Fourier transform. I show that in both cases the same very unusual combination of signatures from chaotic and from integrable dynamics arises.
Meyers, Steven D.
codes at usfweb2.usf.edu/supplierdiversity/how_to_do_business_with_usf.htm) Taxpayer Identification of perjury, I certify that: 1. The number shown on this form is my correct taxpayer identification number (or a TIN on Page 3. University of South Florida Request for Taxpayer Identification Number
Topological Characterization of Extended Quantum Ising Models
G. Zhang; Z. Song
2015-10-27
We show that a class of exactly solvable quantum Ising models, including the transverse-field Ising model and anisotropic XY model, can be characterized as the loops in a two-dimensional auxiliary space. The transverse-field Ising model corresponds to a circle and the XY model corresponds to an ellipse, while other models yield cardioid, limacon, hypocycloid, and Lissajous curves etc. It is shown that the variation of the ground state energy density, which is a function of the loop, experiences a nonanalytical point when the winding number of the corresponding loop changes. The winding number can serve as a topological quantum number of the quantum phases in the extended quantum Ising model, which sheds some light upon the relation between quantum phase transition and the geometrical order parameter characterizing the phase diagram.
Bingjie Xu; Xiang Peng; Hong Guo
2010-10-08
A passive scheme with a beam splitter and a photon-number-resolving (PNR) detector is proposed to verify the photon statistics of an untrusted source in a plug-and-play quantum-key-distribution system by applying a three-intensity decoy-state protocol. The practical issues due to statistical fluctuation and detection noise are analyzed. The simulation results show that the scheme can work efficiently when the total number of optical pulses sent from Alice to Bob is above 10^8, and the dark count rate of the PNR detector is below 0.5 counts/pulse, which is realizable with current techniques. Furthermore, we propose a practical realization of the PNR detector with a variable optical attenuator combined with a threshold detector.
Shepelyansky, Dima
in Quantum Computing of Quantum Chaos and Localization B. Georgeot and D. L. Shepelyansky Laboratoire de exponentially faster than classical algorithms. This shows that important physical problems of quantum chaos]. The corresponding quantum dynamics, called quantum chaos, demonstrates a rich and complex behavior even for systems
Entanglement Routers via Wireless Quantum Network Based on Arbitrary Two Qubit Systems
N. Metwally
2014-05-02
A wireless quantum network is generated between multi-hop, where each hop consists of two entangled nodes. These nodes share a finite number of entangled two qubit systems randomly. Different types of wireless quantum bridges are generated between the non-connected nodes. The efficiency of these wireless quantum bridges to be used as quantum channels between its terminals to perform quantum teleportation is investigated. We suggest a theoretical wireless quantum communication protocol to teleport unknown quantum signals from one node to another, where the more powerful wireless quantum bridges are used as quantum channels. It is shown that, by increasing the efficiency of the sources which emit the initial partial entangled states, one can increase the efficiency of the wireless quantum communication protocol.
Santa Fe New Mexican: For cybersecurity, in quantum encryption...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
quantum encryption we trust Los Alamos physicists developed a quantum random number generator and a quantum communication system, which exploit the laws of quantum physics to...
Nguyen Ba An
2006-02-28
Absolutely and asymptotically secure protocols for organizing an exam in a quantum way are proposed basing judiciously on multipartite entanglement. The protocols are shown to stand against common types of eavesdropping attack.
Smith, Bradley D.
phosphatidylethanolamine PIPn phosphoinositide polyphosphate TREN tris(aminoethyl)amine Introduction The facilitated/threonine side-chain hydroxyl groups, and positive helix dipoles (N-terminal ends); whereas cation selectivity
Algebraic Solutions for $U^{BF}(5)-O^{BF}(6)$ Quantum Phase Transition in Odd Mass Number Nuclei
M. A. Jafarizadeh; M. Ghapanvari; N. Fouladi
2015-09-17
The spherical to deformed $\\gamma -unstable$ shape- phase transition in odd-A nuclei is investigated by using the Dual algebraic structures and the affine $SU(1,1)$ Lie Algebra within the framework of the interacting boson - fermion model. The new algebraic solution for A-odd nuclei is introduced. In this model, Single $j = 1/2 $ and $ 3/2 $ fermions are coupled with an even-even boson core. Energy spectra, quadruple electromagnetic transitions and an expectation value of the d-boson number operator are presented. Experimental evidence for the $U^{BF} (5)-O^{BF} (6)$ transition in odd -A $Ba$ and $Rh$ isotopes is presented. The low-states energy spectra and $B(E2)$values for these nuclei have been also calculated and compared with the experimental data.
Federico Holik
2011-12-20
Since its origins, Quantum mechanics has presented problems with the concept of individuality. It is argued that quantum particles do not have individuality, and so, one can speak about "entities without identity". On the contrary, we claim that the problem of quantum non individuality goes deeper, and that one of its most important features is the fact that there are quantum systems for which particle number is not well defined. In this work, we continue this discussion in relation to the problem about the one and the many.
Hohls, Frank
VOLUME 86, NUMBER 22 P H Y S I C A L R E V I E W L E T T E R S 28 MAY 2001 High Frequency the complex conductivity sxx of a two-dimensional electron system in the quantum Hall regime up to frequencies can be scaled to a single function for different frequencies and several tran- sitions between
Glazman, Leonid
Effect in a Quantum Dot by External Irradiation A. Kaminski,1 Yu. V. Nazarov,2 and L. I. Glazman1 1 of Technology, 2600 GA Delft, The Netherlands (Received 2 April 1999) We demonstrate that external irradiation on the power of the irradiation, this dependence being determined by the decoherence. PACS numbers: 73.23.Hk
Mandelis, Andreas
-RADIATIVE QUANTUM EFFICIENCY OF URANYL FORMATE MONOHYDRATE, LJ0,(HCOO)Z~H20. POWDERS Andreas MANDELIS Rccervcd 28 June 1982 The non-radlaflvc quantum cftic~cncy for the Sy - Sg tmns~t~on III the uranyl formatc in the PAS stgnrtlstrength at 1111swavelength not observed 1n tfie optic31 spectrum The uranyl formate
Kane, Charles
magnetic field B. The model could be rele- vant for semiconductor quantum wires, ropes of carbon nanotubes in which interwire Josephson, charge- and spin-density wave, and single-particle couplings are irrele- vant
Quantum histories without contrary inferences
Losada, Marcelo; Laura, Roberto
2014-12-15
In the consistent histories formulation of quantum theory it was shown that it is possible to retrodict contrary properties. We show that this problem do not appear in our formalism of generalized contexts for quantum histories. - Highlights: • We prove ordinary quantum mechanics has no contrary properties. • Contrary properties in consistent histories are reviewed. • We prove generalized contexts for quantum histories have no contrary properties.
Palffy-Muhoray, Peter
Chapter 21 Nonlinear Susceptibility In the case of linear polarizability, we have shown that the electron may be thought of as being bound by a simple harmonic potential U = 1 2 k1x2 . ( Re- call , and solid is In case of non-linear response, the potential is anharmonic; that is, there are correction
VARIABILITY OF NEARSURFACE ZOOPLANKTON OFF SOUTHERN CALIFORNIA, AS SHOWN BY TOWED-PUMP SAMPLING
VARIABILITY OF NEAR·SURFACE ZOOPLANKTON OFF SOUTHERN CALIFORNIA, AS SHOWN BY TOWED-PUMP SAMPLING Cl of 1962. Samples were collected with a towed pump at a depth of 5 m. Allproximately 162 samples, each repl pump surveys re- llorted here were undertaken to obtain informa- tion on variability and trends
Matrix Inverses Consider the ordinary algebraic equation and its solution shown below
Lee, Carl
Matrix Inverses Consider the ordinary algebraic equation and its solution shown below: Since the linear system can be written as where , , and , (A = coefficient matrix, x = variable vector, b = constant vector) it is reasonable to ask if the matrix equation corresponding to above system of n linear
Foulger, G. R.
Reservoir depletion at The Geysers geothermal area, California, shown by four-dimensional seismic geothermal exploitation at The Geysers geothermal area, California, induces myriads of small of Vp, Vs, and Vp/Vs is an effective geothermal reservoir depletion monitoring tool and can potentially
Colle, C; Cosyn, W; Korover, I; Piasetzky, E; Ryckebusch, J; Weinstein, L B
2015-01-01
The nuclear mass dependence of the number of short-range correlated (SRC) proton-proton (pp) and proton-neutron (pn) pairs in nuclei is a sensitive probe of the dynamics of short-range pairs in the ground state of atomic nuclei. This work presents an analysis of electroinduced single-proton and two-proton knockout measurements off 12C, 27Al, 56Fe, and 208Pb in kinematics dominated by scattering off SRC pairs. The nuclear mass dependence of the observed A(e,e'pp)/12C(e,e'pp) cross-section ratios and the extracted number of pp- and pn-SRC pairs are much softer than the mass dependence of the total number of possible pairs. This is in agreement with a physical picture of SRC affecting predominantly nucleon-nucleon pairs in a nodeless relative-S state of the mean-field basis.
Wladyslaw A. Majewski; Marcin Marciniak
2005-10-28
It was shown that quantum analysis constitutes the proper analytic basis for quantization of Lyapunov exponents in the Heisenberg picture. Differences among various quantizations of Lyapunov exponents are clarified.
Efficiency in Quantum Key Distribution Protocols with Entangled Gaussian States
C. Rodó; O. Romero-Isart; K. Eckert; A. Sanpera
2007-03-21
Quantum key distribution (QKD) refers to specific quantum strategies which permit the secure distribution of a secret key between two parties that wish to communicate secretly. Quantum cryptography has proven unconditionally secure in ideal scenarios and has been successfully implemented using quantum states with finite (discrete) as well as infinite (continuous) degrees of freedom. Here, we analyze the efficiency of QKD protocols that use as a resource entangled gaussian states and gaussian operations only. In this framework, it has already been shown that QKD is possible (M. Navascu\\'es et al. Phys. Rev. Lett. 94, 010502 (2005)) but the issue of its efficiency has not been considered. We propose a figure of merit (the efficiency $E$) to quantify the number of classical correlated bits that can be used to distill a key from a sample of $N$ entangled states. We relate the efficiency of the protocol to the entanglement and purity of the states shared between the parties.
Quantum Equivalence and Quantum Signatures in Heat Engines
Raam Uzdin; Amikam Levy; Ronnie Kosloff
2015-04-15
Quantum heat engines (QHE) are thermal machines where the working substance is quantum. In the extreme case the working medium can be a single particle or a few level quantum system. The study of QHE has shown a remarkable similarity with the standard thermodynamical models, thus raising the issue what is quantum in quantum thermodynamics. Our main result is thermodynamical equivalence of all engine type in the quantum regime of small action. They have the same power, the same heat, the same efficiency, and they even have the same relaxation rates and relaxation modes. Furthermore, it is shown that QHE have quantum-thermodynamic signature, i.e thermodynamic measurements can confirm the presence of quantum coherence in the device. The coherent work extraction mechanism enables power outputs that greatly exceed the power of stochastic (dephased) engines.
A short remark on negative energy densities and quantum inequalities
Dan Solomon
2009-01-20
In quantum field theory it is generally known that the energy density may be negative at a given point in spacetime. A number of papers have shown that there is a restriction on this energy density which is called a quantum inequality (QI). A QI is the lower bound to the "weighted average" of the energy density at a given point integrated over a time dependent sampling function. In this paper we give an example of a sampling function for which there is no QI.
Anirban Pathak
2014-11-24
Recently, Hassanpour and Houshmand have proposed a protocol of controlled deterministic secure quantum communication (Quant. Info. Process, DOI 10.1007/s11128-014-0866-z (2014)). The authors compared the efficiency of their protocol with that of two other existing protocols and claimed that their protocol is efficient. Here, we have shown that the efficiency of Hassanpour Houshmand (HH) protocol is not high, and there exist several approaches through which more efficient protocols for the same task can be designed. To establish this point, we have proposed an efficient protocol of controlled deterministic secure quantum communication which is based on permutation of particles (PoP) technique and is considerably efficient compared to HH protocol. We have also generalized this protocol into its bidirectional counterpart. Interestingly, bipartite entanglement (Bell state) is sufficient for the realization of the proposed protocols, but HH protocol and other existing protocols require at least tripartite entanglement. Further, we have shown that it is possible to construct a large number of efficient protocols of unidirectional and bidirectional controlled deterministic secure quantum communication by using various alternative approaches and different quantum states. These alternative protocols can be realized by modifying the existing protocols of quantum secure direct communication and deterministic secure quantum communication. We have also shown that it is possible to design completely orthogonal-state-based protocols for unidirectional and bidirectional controlled deterministic secure quantum communication.
Suppression of quantum chaos in a quantum computer hardware
Lages, J.; Shepelyansky, D. L. [Laboratoire de Physique Theorique, UMR 5152 du CNRS, Universite Paul Sabatier, 31062 Toulouse Cedex 4 (France)
2006-08-15
We present numerical and analytical studies of a quantum computer proposed by the Yamamoto group in Phys. Rev. Lett. 89, 017901 (2002). The stable and quantum chaos regimes in the quantum computer hardware are identified as a function of magnetic field gradient and dipole-dipole couplings between qubits on a square lattice. It is shown that a strong magnetic field gradient leads to suppression of quantum chaos.
Suppression of quantum chaos in a quantum computer hardware
J. Lages; D. L. Shepelyansky
2005-10-14
We present numerical and analytical studies of a quantum computer proposed by the Yamamoto group in Phys. Rev. Lett. 89, 017901 (2002). The stable and quantum chaos regimes in the quantum computer hardware are identified as a function of magnetic field gradient and dipole-dipole couplings between qubits on a square lattice. It is shown that a strong magnetic field gradient leads to suppression of quantum chaos.
Selectivity in multiple quantum nuclear magnetic resonance
Warren, W.S.
1980-11-01
The observation of multiple-quantum nuclear magnetic resonance transitions in isotropic or anisotropic liquids is shown to give readily interpretable information on molecular configurations, rates of motional processes, and intramolecular interactions. However, the observed intensity of high multiple-quantum transitions falls off dramatically as the number of coupled spins increases. The theory of multiple-quantum NMR is developed through the density matrix formalism, and exact intensities are derived for several cases (isotropic first-order systems and anisotropic systems with high symmetry) to shown that this intensity decrease is expected if standard multiple-quantum pulse sequences are used. New pulse sequences are developed which excite coherences and produce population inversions only between selected states, even though other transitions are simultaneously resonant. One type of selective excitation presented only allows molecules to absorb and emit photons in groups of n. Coherent averaging theory is extended to describe these selective sequences, and to design sequences which are selective to arbitrarily high order in the Magnus expansion. This theory and computer calculations both show that extremely good selectivity and large signal enhancements are possible.
All inorganic colloidal quantum dot LEDs
Wood, Vanessa Claire
2007-01-01
This thesis presents the first colloidal quantum dot light emitting devices (QD-LEDs) with metal oxide charge transport layers. Colloidally synthesized quantum dots (QDs) have shown promise as the active material in ...
Sun, Yu
medium exchange · Develop alterna@ve so\\ware environment to simplify· Constructs have shown success in replacement of large- diameter vessels (e) constructs have shown more failure rates, resul@ng in aneurysm forma
Flambaum, V.V.; Izrailev, F.M. [School of Physics, University of New South Wales, Sydney 2052 (Australia)] [School of Physics, University of New South Wales, Sydney 2052 (Australia)
1997-01-01
A method is developed for calculation of single-particle occupation numbers in finite Fermi systems of interacting particles. It is more accurate than the canonical distribution method and gives the Fermi-Dirac distribution in the limit of large number of particles. It is shown that statistical effects of the interaction are absorbed by an increase of the effective temperature. Criteria for quantum chaos and statistical equilibrium are considered. All results are confirmed by numerical experiments in the two-body random interaction model. {copyright} {ital 1997} {ital The American Physical Society}
von Oppen, Felix
Statistics: A Criterion for Quantum Chaos Galya Blum, Sven Gnutzmann, and Uzy Smilansky The Weizmann independent). Thus, a new criterion for quantum chaos is provided by the statistics of the wave functions themes of quantum chaos [16]. Here, we present a new approach which is based on the distribution
Stafford, Charles
in Metallic Nanocohesion: A Quantum Chaos Approach C. A. Stafford,1,2,3 F. Kassubek,1,2,3 J. Bürki,1 from quantum chaos [1215] to describe the quantum mechanics of such an open system. It is found
Stockman, Mark I.
and Spatial Correlation of Currents in Quantum Chaos John R. Evans and Mark I. Stockman* Department of Physics of quantum chaos [1] became experimentally observable in a variety of physical systems. One of the most actively studied classes of such systems are semiconductor heterostructures [2,3]. Quantum chaos affects
Wilkinson, Michael
for Quantum Chaos on a Torus Itzhack Dana,1 Mario Feingold,2 and Michael Wilkinson3 1 Department of Physics in the field of quantum chaos, can be reduced to a torus, either in configuration space (e.g., the Sinai in the quantum-chaos literature [4Â12], although attention has often been confined to strict periodicity. General
Superradiant Quantum Heat Engine
Ali Ü. C. Hardal; Özgür E. Müstecapl?oglu
2015-07-16
Quantum physics revolutionized classical disciplines of mechanics, statistical physics, and electrodynamics. One branch of scientific knowledge however seems untouched: thermodynamics. Major motivation behind thermodynamics is to develop efficient heat engines. Technology has a trend to miniaturize engines, reaching to quantum regimes. Development of quantum heat engines (QHEs) requires emerging field of quantum thermodynamics. Studies of QHEs debate whether quantum coherence can be used as a resource. We explore an alternative where it can function as an effective catalyst. We propose a QHE which consists of a photon gas inside an optical cavity as the working fluid and quantum coherent atomic clusters as the fuel. Utilizing the superradiance, where a cluster can radiate quadratically faster than a single atom, we show that the work output becomes proportional to the square of the number of the atoms. In addition to practical value of cranking up QHE, our result is a fundamental difference of a quantum fuel from its classical counterpart.
Superradiant Quantum Heat Engine
Ali Ü. C. Hardal; Özgür E. Müstecapl?oglu
2015-04-22
Quantum physics revolutionized classical disciplines of mechanics, statistical physics, and electrodynamics. One branch of scientific knowledge however seems untouched: thermodynamics. Major motivation behind thermodynamics is to develop efficient heat engines. Technology has a trend to miniaturize engines, reaching to quantum regimes. Development of quantum heat engines (QHEs) requires emerging field of quantum thermodynamics. Studies of QHEs debate whether quantum coherence can be used as a resource. We explore an alternative where it can function as an effective catalyst. We propose a QHE which consists of a photon gas inside an optical cavity as the working fluid and quantum coherent atomic clusters as the fuel. Utilizing the superradiance, where a cluster can radiate quadratically faster than a single atom, we show that the work output becomes proportional to the square of the number of the atoms. In addition to practical value of cranking up QHE, our result is a fundamental difference of a quantum fuel from its classical counterpart.
Fault-tolerant quantum computer architectures using hierarchies of quantum error-correcting codes
Cross, Andrew W. (Andrew William), 1979-
2008-01-01
Quantum computers have been shown to efficiently solve a class of problems for which no efficient solution is otherwise known. Physical systems can implement quantum computation, but devising realistic schemes is an extremely ...
Physical interpretation of Jeans instability in quantum plasmas
Akbari-Moghanjoughi, M.
2014-08-15
In this paper, we use the quantum hydrodynamics and its hydrostatic limit to investigate the newly posed problem of Jeans instability in quantum plasmas from a different point of view in connection with the well-known Chandrasekhar mass-limit on highly collapsed degenerate stellar configurations. It is shown that the hydrodynamic stability of a spherically symmetric uniform quantum plasma with a given fixed mass is achieved by increase in its mass-density or decrease in the radius under the action of gravity. It is also remarked that for masses beyond the limiting Jeans-mass, the plasma becomes completely unstable and the gravitational collapse would proceed forever. This limiting mass is found to depend strongly on the composition of the quantum plasma and the atomic-number of the constituent ions, where it is observed that heavier elements rather destabilize the quantum plasma hydrodynamically. It is also shown that the Chandrasekhar mass-limit for white dwarf stars can be directly obtained from the hydrostatic limit of our model.
Quantum cards and quantum rods
Milan Batista; Joze Peternelj
2006-11-02
Quantum mechanical analysis of a rigid rod with one end fixed to a flat table is presented. It is shown, that for a macroscopic rod the ground state is orientationally delocalized only if the table is absolutely horizontal. In this latter case the rod, assumed to be initally in the upright orientation, falls down symmetrically and simultaneously in both directions, as claimed by Tegmark and Wheeler. In addition, the time of fall is calculated using WKB wavefunctions representing energy eigenstates near the barrier summit.
Askin cream developed and tested by UAB Professor Mohammad Athar, Ph.D., has shown it can hyper-
Bedwell, David M.
. The cream could one day be added to sunscreen as a cancer-fighting ingredient if it is shown to have
Invariance in adelic quantum mechanics
Branko Dragovich
2006-12-07
Adelic quantum mechanics is form invariant under an interchange of real and p-adic number fields as well as rings of p-adic integers. We also show that in adelic quantum mechanics Feynman's path integrals for quadratic actions with rational coefficients are invariant under changes of their entries within nonzero rational numbers.
Information and noise in quantum measurement
Holger F. Hofmann
2000-03-30
Even though measurement results obtained in the real world are generally both noisy and continuous, quantum measurement theory tends to emphasize the ideal limit of perfect precision and quantized measurement results. In this article, a more general concept of noisy measurements is applied to investigate the role of quantum noise in the measurement process. In particular, it is shown that the effects of quantum noise can be separated from the effects of information obtained in the measurement. However, quantum noise is required to ``cover up'' negative probabilities arising as the quantum limit is approached. These negative probabilities represent fundamental quantum mechanical correlations between the measured variable and the variables affected by quantum noise.
Simulated Quantum Computation of Molecular Energies
Alán Aspuru-Guzik; Anthony D. Dutoi; Peter J. Love; Martin Head-Gordon
2006-04-26
The calculation time for the energy of atoms and molecules scales exponentially with system size on a classical computer but polynomially using quantum algorithms. We demonstrate that such algorithms can be applied to problems of chemical interest using modest numbers of quantum bits. Calculations of the water and lithium hydride molecular ground-state energies have been carried out on a quantum computer simulator using a recursive phase-estimation algorithm. The recursive algorithm reduces the number of quantum bits required for the readout register from about 20 to 4. Mappings of the molecular wave function to the quantum bits are described. An adiabatic method for the preparation of a good approximate ground-state wave function is described and demonstrated for a stretched hydrogen molecule. The number of quantum bits required scales linearly with the number of basis functions, and the number of gates required grows polynomially with the number of quantum bits.
Markus Arndt; Thomas Juffmann; Vlatko Vedral
2009-11-01
Quantum physics and biology have long been regarded as unrelated disciplines, describing nature at the inanimate microlevel on the one hand and living species on the other hand. Over the last decades the life sciences have succeeded in providing ever more and refined explanations of macroscopic phenomena that were based on an improved understanding of molecular structures and mechanisms. Simultaneously, quantum physics, originally rooted in a world view of quantum coherences, entanglement and other non-classical effects, has been heading towards systems of increasing complexity. The present perspective article shall serve as a pedestrian guide to the growing interconnections between the two fields. We recapitulate the generic and sometimes unintuitive characteristics of quantum physics and point to a number of applications in the life sciences. We discuss our criteria for a future quantum biology, its current status, recent experimental progress and also the restrictions that nature imposes on bold extrapolations of quantum theory to macroscopic phenomena.
Hyper-Hamiltonian quantum mechanics
Vladimir Trifonov
2006-03-02
We present a modification of quantum mechanics with a *possible worlds* semantics. It is shown that `gauge' degrees of freedom along possible worlds can be used to encode gravitational information.
Danilov, Viatcheslav; /Oak Ridge; Nagaitsev, Sergei; /Fermilab
2011-11-01
Many quantum integrable systems are obtained using an accelerator physics technique known as Ermakov (or normalized variables) transformation. This technique was used to create classical nonlinear integrable lattices for accelerators and nonlinear integrable plasma traps. Now, all classical results are carried over to a nonrelativistic quantum case. In this paper we have described an extension of the Ermakov-like transformation to the Schroedinger and Pauli equations. It is shown that these newly found transformations create a vast variety of time dependent quantum equations that can be solved in analytic functions, or, at least, can be reduced to time-independent ones.
Quantum measurement and decoherence
G. W. Ford; J. T. Lewis; R. F. O'Connell
2003-01-13
Distribution functions defined in accord with the quantum theory of measurement are combined with results obtained from the quantum Langevin equation to discuss decoherence in quantum Brownian motion. Closed form expressions for wave packet spreading and the attenuation of coherence of a pair of wave packets are obtained. The results are exact within the context of linear passive dissipation. It is shown that, contrary to widely accepted current belief, decoherence can occur at high temperature in the absence of dissipation. Expressions for the decoherence time with and without dissipation are obtained that differ from those appearing in earlier discussions.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity ofkandz-cm11 OutreachProductswsicloudwsiclouddenDVA N C E D BGene Network ShapingDate: M-16-04-04 Federal FacilityChange Number
Bohmian mechanics contradicts quantum mechanics
Neumaier, Arnold
Bohmian mechanics contradicts quantum mechanics Arnold Neumaier Institut fur Mathematik, Universit://solon.cma.univie.ac.at/#24;neum/ Abstract. It is shown that, for a harmonic oscillator in the ground state, Bohmian mechanics and quantum mechanics predict values of opposite sign for certain time correlations. The discrepancy can
Ludwig-Maximilians-Universität, München
of semiconductors seems to dominate optoelectronic properties since the strength of interband transitions is largely expose a semiconductor quantum well of a direct gap material to a moving potential superlattice modulated accompanying a surface acoustic wave on a semiconductor quantum well structure are employed to dissociate
Modulational instability of electromagnetic waves in a collisional quantum magnetoplasma
Niknam, A. R.; Rastbood, E.; Bafandeh, F.; Khorashadizadeh, S. M.
2014-04-15
The modulational instability of right-hand circularly polarized electromagnetic electron cyclotron (CPEM-EC) wave in a magnetized quantum plasma is studied taking into account the collisional effects. Employing quantum hydrodynamic and nonlinear Schrödinger equations, the dispersion relation of modulated CPEM-EC wave in a collisional plasma has been derived. It is found that this wave is unstable in such a plasma system and the growth rate of the associated instability depends on various parameters such as electron Fermi temperature, plasma number density, collision frequency, and modulation wavenumber. It is shown that while the increase of collision frequency leads to increase of the growth rate of instability, especially at large wavenumber limit, the increase of plasma number density results in more stable modulated CPEM-EC wave. It is also found that in contrast to collisionless plasma in which modulational instability is restricted to small wavenumbers, in collisional plasma, the interval of instability occurrence can be extended to a large domain.
Quantum phase transitions of the Dirac oscillator in a minimal length scenario
L. Menculini; O. Panella; P. Roy
2014-11-19
We obtain exact solutions of the (2+1) dimensional Dirac oscillator in a homogeneous magnetic field within a minimal length ($\\Delta x_0=\\hbar \\sqrt{\\beta}$), or generalised uncertainty principle (GUP) scenario. This system in ordinary quantum mechanics has a single left-right chiral quantum phase transition (QPT). We show that a non zero minimal length turns on a infinite number of quantum phase transitions which accumulate towards the known QPT when $\\beta \\to 0$. It is also shown that the presence of the minimal length modifies the degeneracy of the states and that in this case there exist a new class of states which do not survive in the ordinary quantum mechanics limit $\\beta \\to 0$.
QUANTUM CHAOS IN QUANTUM NETWORKS()
Shepelyansky, Dima
QUANTUM CHAOS IN QUANTUM NETWORKS() Chepelianskii Alexei LycÂ´ee Pierre de Fermat and Quantware MIPS Computers and Quantum Chaos", June 28 - 30, 2001, Villa Olmo, Como, Italy #12;SHORT DESCRIPTION OF THE RESULTS Quantum chaos in a quantum small world We introduce and study a quantum small world model
Shepelyansky, Dima
Entanglement versus relaxation and decoherence in a quantum algorithm for quantum chaos S. Bettelli in a quantum computer operating an efficient algorithm for quantum chaos. Our results show that in an ideal of quantum chaos with a small number of qubits. Since the entanglement can be efficiently measured experi
Gevorgyan, T. V. [Institute for Physical Research, National Academy of Sciences, Ashtarak-2, 0203 Ashtarak (Armenia); Shahinyan, A. R. [Yerevan State University, A. Manoogian 1, 0025 Yerevan (Armenia); Kryuchkyan, G. Yu. [Institute for Physical Research, National Academy of Sciences, Ashtarak-2, 0203 Ashtarak (Armenia); Yerevan State University, A. Manoogian 1, 0025 Yerevan (Armenia)
2009-05-15
We show that quantum-interference phenomena can be realized for the dissipative nonlinear systems exhibiting hysteresis-cycle behavior and quantum chaos. Such results are obtained for a driven dissipative nonlinear oscillator with time-dependent parameters and take place for the regimes of long time intervals exceeding dissipation time and for macroscopic levels of oscillatory excitation numbers. Two schemas of time modulation, (i) periodic variation in the strength of the {chi}(3) nonlinearity; (ii) periodic modulation of the amplitude of the driving force, are considered. These effects are obtained within the framework of phase-space quantum distributions. It is demonstrated that the Wigner functions of oscillatory mode in both bistable and chaotic regimes acquire negative values and interference patterns in parts of phase-space due to appropriately time modulation of the oscillatory nonlinear dynamics. It is also shown that the time modulation of the oscillatory parameters essentially improves the degree of sub-Poissonian statistics of excitation numbers.
Suppression of quantum chaos in a quantum computer hardware J. Lages* and D. L. Shepelyansky
Shepelyansky, Dima
Suppression of quantum chaos in a quantum computer hardware J. Lages* and D. L. Shepelyansky computer proposed by the Yamamoto group in Phys. Rev. Lett. 89, 017901 2002 . The stable and quantum chaos gradient leads to suppression of quantum chaos. DOI: 10.1103/PhysRevE.74.026208 PACS number s : 05.45.Mt
Recoverability in quantum information theory
Wilde, Mark M
2015-01-01
The fact that the quantum relative entropy is non-increasing with respect to quantum physical evolutions lies at the core of many optimality theorems in quantum information theory and has applications in other areas of physics. In this work, we establish improvements of this entropy inequality in the form of physically meaningful remainder terms. One of the main results can be summarized informally as follows: if the decrease in quantum relative entropy between two quantum states after a quantum physical evolution is relatively small, then it is possible to perform a recovery operation, such that one can perfectly recover one state while approximately recovering the other. This can be interpreted as quantifying how well one can reverse a quantum physical evolution. Our proof method is elementary, relying on the method of complex interpolation, basic linear algebra, and the recently introduced Renyi generalization of a relative entropy difference. The theorem has a number of applications in quantum information...
Schwinger, Pegg and Barnett and a relationship between angular and Cartesian quantum descriptions
M. Ruzzi
2002-01-08
From a development of an original idea due to Schwinger, it is shown that it is possible to recover, from the quantum description of a degree of freedom characterized by a finite number of states (\\QTR{it}{i.e}., without classical counterpart) the usual canonical variables of position/momentum \\QTR{it}{and} angle/angular momentum, relating, maybe surprisingly, the first as a limit of the later.
Quantum computing for pattern classification
Maria Schuld; Ilya Sinayskiy; Francesco Petruccione
2014-12-11
It is well known that for certain tasks, quantum computing outperforms classical computing. A growing number of contributions try to use this advantage in order to improve or extend classical machine learning algorithms by methods of quantum information theory. This paper gives a brief introduction into quantum machine learning using the example of pattern classification. We introduce a quantum pattern classification algorithm that draws on Trugenberger's proposal for measuring the Hamming distance on a quantum computer (CA Trugenberger, Phys Rev Let 87, 2001) and discuss its advantages using handwritten digit recognition as from the MNIST database.
Stapp, Henry
2011-11-10
Robert Griffiths has recently addressed, within the framework of a ‘consistent quantum theory’ (CQT) that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues, on the basis of his examination of certain arguments that claim to demonstrate the existence of such nonlocal influences, that such influences do not exist. However, his examination was restricted mainly to hidden-variable-based arguments that include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. One cannot logically prove properties of a system by attributing to the system properties alien to that system. Hence Griffiths’ rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence for nonlocal influences. But he did not examine the particular proof that he cites. An examination of that particular proof by the method specified by his ‘consistent quantum theory’ shows that the cited proof is valid within that restrictive framework. This necessary existence, within the ‘consistent’ framework, of long range essentially instantaneous influences refutes the claim made by Griffiths that his ‘consistent’ framework is superior to the orthodox quantum theory of von Neumann because it does not entail instantaneous influences. An added section responds to Griffiths’ reply, which cites a litany of ambiguities that seem to restrict, devastatingly, the scope of his CQT formalism, apparently to buttress his claim that my use of that formalism to validate the nonlocality theorem is flawed. But the vagaries that he cites do not upset the proof in question. It is show here in detail why the precise statement of this theorem justifies the specified application of CQT. It is also shown, in response to his challenge, why a putative proof of locality that he has proposed is not valid.
On the Existence of certain Quantum Algorithms
Bjoern Grohmann
2009-04-11
We investigate the question if quantum algorithms exist that compute the maximum of a set of conjugated elements of a given number field in quantum polynomial time. We will relate the existence of these algorithms for a certain family of number fields to an open conjecture from elementary number theory.
Super-radiance and open quantum systems
Volya, Alexander [Department of Physics, Florida State University, Tallahassee, FL 32306-4350 (United States); Zelevinsky, Vladimir [NSCL, Michigan State University, East Lansing, MI 48824-1321 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-1321 (United States)
2005-07-08
Quantum wires, loosely bound nuclei, molecules in chemical reactions and exotic narrow pentaquark states are different examples of open quantum mesoscopic systems. The coupling with and through continuum is their common feature. We discuss general properties of quantum systems in the regime of strong continuum coupling, when the mechanism of Dicke super-radiance changes intrinsic dynamics, signatures of quantum chaos, lifetime of unstable states and reaction cross sections. The examples are shown for various areas of mesoscopic physics.
Decoherence in adiabatic quantum computation
Tameem Albash; Daniel A. Lidar
2015-06-19
Recent experiments with increasingly larger numbers of qubits have sparked renewed interest in adiabatic quantum computation, and in particular quantum annealing. A central question that is repeatedly asked is whether quantum features of the evolution can survive over the long time-scales used for quantum annealing relative to standard measures of the decoherence time. We reconsider the role of decoherence in adiabatic quantum computation and quantum annealing using the adiabatic quantum master equation formalism. We restrict ourselves to the weak-coupling and singular-coupling limits, which correspond to decoherence in the energy eigenbasis and in the computational basis, respectively. We demonstrate that decoherence in the instantaneous energy eigenbasis does not necessarily detrimentally affect adiabatic quantum computation, and in particular that a short single-qubit $T_2$ time need not imply adverse consequences for the success of the quantum adiabatic algorithm. We further demonstrate that boundary cancellation methods, designed to improve the fidelity of adiabatic quantum computing in the closed system setting, remain beneficial in the open system setting. To address the high computational cost of master equation simulations, we also demonstrate that a quantum Monte Carlo algorithm that explicitly accounts for a thermal bosonic bath can be used to interpolate between classical and quantum annealing. Our study highlights and clarifies the significantly different role played by decoherence in the adiabatic and circuit models of quantum computing.
Quantum correlation cost of the weak measurement
Jun Zhang; Shao-xiong Wu; Chang-shui Yu
2014-09-14
Quantum correlation cost (QCC) characterizing how much quantum correlation is used in a weak-measurement process is presented based on the trace norm. It is shown that the QCC is related to the trace-norm-based quantum discord (TQD) by only a factor that is determined by the strength of the weak measurement, so it only catches partial quantumness of a quantum system compared with the TQD. We also find that the residual quantumness can be `extracted' not only by the further von Neumann measurement, but also by a sequence of infinitesimal weak measurements. As an example, we demonstrate our outcomes by the Bell-diagonal state.
Beigl, Michael
consumption and for about 50% of the total electricity consumption [1]. Therefore it is important to explore one of them. The interviewees preferred receiving electricity consumption feedback from a bill, a web1 Abstract--Numerous studies have shown that households' consumption is an important part
Tolbert, Leon M.
in switching applications such as AC motor control, motion/servo control, uninterruptible power suppliesAbstract -- Research on silicon carbide (SiC) power electronics has shown their advantages in high is verified to have low power loss, fast switching characteristics at 650 V dc bus voltage, 60 A drain current
A close-up of the Sun (shown in ultraviolet light) reveals a mottled surface, bright flares,
Christian, Eric
#12;#12;A close-up of the Sun (shown in ultraviolet light) reveals a mottled surface, bright flares, and tongues of hot gas leaping into space. Though they look like burns in the face of the Sun, sunspots circle in the center of the photo--allows scientists to see the solar wind streaming away from the Sun
Quantum Simulator for Transport Phenomena in Fluid Flows
Mezzacapo, A; Lamata, L; Egusquiza, I L; Succi, S; Solano, E
2015-01-01
Transport phenomena are one of the most challenging problems in computational physics. We present a quantum simulator based on pseudospin-boson quantum systems, which is suitable for encoding fluid dynamics problems within a lattice kinetic formalism. This quantum simulator is obtained by exploiting the analogies between Dirac and lattice Boltzmann equations. It is shown that both the streaming and collision processes of lattice Boltzmann dynamics can be implemented with controlled quantum operations, using a heralded quantum protocol to encode non-unitary scattering processes. The proposed simulator is amenable to realization in controlled quantum platforms, such as ion-trap quantum computers or circuit quantum electrodynamics processors.
Termination of Nondeterministic Quantum Programs
Yangjia Li; Nengkun Yu; Mingsheng Ying
2012-01-04
We define a language-independent model of nondeterministic quantum programs in which a quantum program consists of a finite set of quantum processes. These processes are represented by quantum Markov chains over the common state space. An execution of a nondeterministic quantum program is modeled by a sequence of actions of individual processes. These actions are described by super-operators on the state Hilbert space. At each step of an execution, a process is chosen nondeterministically to perform the next action. A characterization of reachable space and a characterization of diverging states of a nondeterministic quantum program are presented. We establish a zero-one law for termination probability of the states in the reachable space of a nondeterministic quantum program. A combination of these results leads to a necessary and sufficient condition for termination of nondeterministic quantum programs. Based on this condition, an algorithm is found for checking termination of nondeterministic quantum programs within a fixed finite-dimensional state space. A striking difference between nondeterministic classical and quantum programs is shown by example: it is possible that each of several quantum programs simulates the same classical program which terminates with probability 1, but the nondeterministic program consisting of them terminates with probability 0 due to the interference carried in the execution of them.
Delocalization and quantum chaos in atom-field systems
M. A. Bastarrachea-Magnani; B. López-del-Carpio; J. Chávez-Carlos; S. Lerma-Hernández; J. G. Hirsch
2015-09-19
Employing efficient diagonalization techniques, we perform a detailed quantitative study of the regular and chaotic regions in phase space in the simplest non-integrable atom-field system, the Dicke model. A close correlation between the classical Lyapunov exponents and the quantum Participation Ratio of coherent states on the eigenenergy basis is exhibited for different points in the phase space. It is also shown that the Participation Ratio scales linearly with the number of atoms in chaotic regions, and with its square root in the regular ones.
Record statistics in random vectors and quantum chaos
Srivastava, Shashi C L; Jain, Sudhir R
2012-01-01
The record statistics of complex random states are analytically calculated, and shown that the probability of a record intensity is a Bernoulli process. The correlation due to normalization leads to a probability distribution of the records that is non-universal but tends to the Gumbel distribution asymptotically. The quantum standard map is used to study these statistics for the effect of correlations apart from normalization. It is seen that in the mixed phase space regime the number of intensity records is a power law in the dimensionality of the state as opposed to the logarithmic growth for random states.
Quantum statistical calculation of cluster abundances in hot dense matter
Gerd Ropke
2014-07-01
The cluster abundances are calculated from a quantum statistical approach taking into account in-medium corrections. For arbitrary cluster size the self-energy and Pauli blocking shifts are considered. Exploratory calculations are performed for symmetric matter at temperature $T=5$ MeV and baryon density $\\varrho=0.0156$ fm$^{-3}$ to be compared with the solar element distribution. It is shown that the abundances of weakly bound nuclei with mass number $4
Playing Prisoner's Dilemma with Quantum Rules
Jiangfeng Du; Xiaodong Xu; Hui Li; Xianyi Zhou; Rongdian Han
2003-01-11
Quantum game theory is a recently developing field of physical research. In this paper, we investigate quantum games in a systematic way. With the famous instance of the Prisoner's Dilemma, we present the fascinating properties of quantum games in different conditions, i.e. different number of the players, different strategic space of the players and different amount of the entanglement involved.
Shepelyansky, Dima
statistics of energy level spacings. On the contrary, chaotic dynamics leads to level repulsion where quantum chaos and random matrix level statistics emerge from the integrable limits of weak been intensively investigated in the past decade [1]. It has been realized that the statistical
Mukamel, Shaul
of Physics, University of California at Berkeley, Berkeley, California 94720 Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California at Berkeley, Berkeley, California 94720,2]. In the case of transport the carrier de Broglie wavelength lB determines the length scale at which quantum
Random Numbers Certified by Bell's Theorem
S. Pironio; A. Acin; S. Massar; A. Boyer de la Giroday; D. N. Matsukevich; P. Maunz; S. Olmschenk; D. Hayes; L. Luo; T. A. Manning; C. Monroe
2010-10-19
Randomness is a fundamental feature in nature and a valuable resource for applications ranging from cryptography and gambling to numerical simulation of physical and biological systems. Random numbers, however, are difficult to characterize mathematically, and their generation must rely on an unpredictable physical process. Inaccuracies in the theoretical modelling of such processes or failures of the devices, possibly due to adversarial attacks, limit the reliability of random number generators in ways that are difficult to control and detect. Here, inspired by earlier work on nonlocality based and device independent quantum information processing, we show that the nonlocal correlations of entangled quantum particles can be used to certify the presence of genuine randomness. It is thereby possible to design of a new type of cryptographically secure random number generator which does not require any assumption on the internal working of the devices. This strong form of randomness generation is impossible classically and possible in quantum systems only if certified by a Bell inequality violation. We carry out a proof-of-concept demonstration of this proposal in a system of two entangled atoms separated by approximately 1 meter. The observed Bell inequality violation, featuring near-perfect detection efficiency, guarantees that 42 new random numbers are generated with 99% confidence. Our results lay the groundwork for future device-independent quantum information experiments and for addressing fundamental issues raised by the intrinsic randomness of quantum theory.
The Unreasonable Success of Quantum Probability II: Quantum Measurements as Universal Measurements
Diederik Aerts; Massimiliano Sassoli de Bianchi
2014-09-10
In the first part of this two-part article, we have introduced and analyzed a multidimensional model, called the 'general tension-reduction' (GTR) model, able to describe general quantum-like measurements with an arbitrary number of outcomes, and we have used it as a general theoretical framework to study the most general possible condition of lack of knowledge in a measurement, so defining what we have called a 'universal measurement'. In this second part, we present the formal proof that universal measurements, which are averages over all possible forms of fluctuations, produce the same probabilities as measurements characterized by 'uniform' fluctuations on the measurement situation. Since quantum probabilities can be shown to arise from the presence of such uniform fluctuations, we have proven that they can be interpreted as the probabilities of a first-order non-classical theory, describing situations in which the experimenter lacks complete knowledge about the nature of the interaction between the measuring apparatus and the entity under investigation. This same explanation can be applied -- mutatis mutandis -- to the case of cognitive measurements, made by human subjects on conceptual entities, or in decision processes, although it is not necessarily the case that the structure of the set of states would be in this case strictly Hilbertian. We also show that universal measurements correspond to maximally 'robust' descriptions of indeterministic reproducible experiments, and since quantum measurements can also be shown to be maximally robust, this adds plausibility to their interpretation as universal measurements, and provides a further element of explanation for the great success of the quantum statistics in the description of a large class of phenomena.
A. Yu. Samarin
2015-05-10
The change with time of the system consisting of the quantum object and the macroscopic measuring instrument is described on the base of the uniform dynamic law, which is suitable both evolution and reduction processes description. It is the integral wave equation with kernel in the form of a path integral. It is shown, that wave function collapse is the specific transformation which is fundamentally differ from Shr\\"odinger's evolution. Specifically, a formal cause of the collapse is a local time derivative (infinite large) of the potential energy. Such transformation can not be described using mathematical apparatus of conventional quantum mechanics.
Experimental determination of Ramsey numbers
Zhengbing Bian; Fabian Chudak; William G. Macready; Lane Clark; Frank Gaitan
2013-08-14
Ramsey theory is a highly active research area in mathematics that studies the emergence of order in large disordered structures. Ramsey numbers mark the threshold at which order first appears and are extremely difficult to calculate due to their explosive rate of growth. Recently, an algorithm that can be implemented using adiabatic quantum evolution has been proposed that calculates the two-color Ramsey numbers $R(m,n)$. Here we present results of an experimental implementation of this algorithm and show that it correctly determines the Ramsey numbers R(3,3) and $R(m,2)$ for $4\\leq m\\leq 8$. The R(8,2) computation used 84 qubits of which 28 were computational qubits. This computation is the largest experimental implementation of a scientifically meaningful adiabatic evolution algorithm that has been done to date.
Smagina, Zh. V.; Stepina, N. P., E-mail: stepina@isp.nsc.ru; Zinovyev, V. A.; Kuchinskaya, P. A. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Lavrenteva 13, 630090 Novosibirsk (Russian Federation); Novikov, P. L.; Dvurechenskii, A. V. [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Lavrenteva 13, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova, 2, 630090 Novosibirsk (Russian Federation)
2014-10-13
An original approach based on the combination of nanoimprint lithography and ion irradiation through mask has been developed for fabrication of large-area periodical pattern on Si(100). Using the selective etching of regions amorphized by ion irradiation ordered structures with grooves and ridges were obtained. The shape and depth of the relief were governed by ion energy and by the number of etching stages as well. Laterally ordered chains of Ge quantum dots were fabricated by molecular beam epitaxy of Ge on the pre-patterned Si substrates. For small amount of Ge deposited chains contain separate quantum dot molecules. The increase of deposition amount leads to overlapping of quantum dot molecules with formation of dense homogeneous chains of quantum dots. It was shown that the residual irradiation-induced bulk defects underneath the grooves suppress nucleation of Ge islands at the bottom of grooves. On pre-patterned substrates with whole defect regions, etched quantum dots grow at the bottom of grooves. The observed location of Ge quantum dots is interpreted in terms of local strain-mediated surface chemical potential which controls the sites of islands nucleation. The local chemical potential is affected by additional strain formed by the residual defects. It was shown by molecular dynamics calculations that these defects form the compressive strain at the bottom of grooves.
Quantum interference as a resource for quantum speedup
Dan Stahlke
2014-08-01
Quantum states can in a sense be thought of as generalizations of classical probability distributions, but are more powerful than probability distributions when used for computation or communication. Quantum speedup therefore requires some feature of quantum states that classical probability distributions lack. One such feature is interference. We quantify interference and show that there can be no quantum speedup due to a small number of operations incapable of generating large amounts of interference (although large numbers of such operations can in fact lead to quantum speedup). Low-interference operations include sparse unitaries, Grover reflections, short time/low energy Hamiltonian evolutions, and the Haar wavelet transform. Circuits built from such operations can be classically simulated via a Monte Carlo technique making use of a convex combination of two Markov chains. Applications to query complexity, communication complexity, and the Wigner representation are discussed.
On an example of genuine quantum chaos Department of Physics
On an example of genuine quantum chaos M. Kuna Department of Physics Pedagogical College of S@halina.univ.gda.pl Abstract: The first example of a quantum system with the genuine quantum chaos is presented. PACS numbers the definition of ``quantum chaos''. Several defiÂ nitions exist and their interconnections have not been fully
P. Pfeiffer; I. L. Egusquiza; M. Di Ventra; M. Sanz; E. Solano
2015-11-06
Technology based on memristors, resistors with memory whose resistance depends on the history of the crossing charges, has lately enhanced the classical paradigm of computation with neuromorphic architectures. However, in contrast to the known quantized models of passive circuit elements, such as inductors, capacitors or resistors, the design and realization of a quantum memristor is still missing. Here, we introduce the concept of a quantum memristor as a quantum dissipative device, whose decoherence mechanism is controlled by a continuous-measurement feedback scheme, which accounts for the memory. Indeed, we provide numerical simulations showing that memory effects actually persist in the quantum regime. Our quantization method, specifically designed for superconducting circuits, may be extended to other quantum platforms, allowing for memristor-type constructions in different quantum technologies. The proposed quantum memristor is then a building block for neuromorphic quantum computation and quantum simulations of non-Markovian systems.
Michele Mosca
2008-08-04
This article surveys the state of the art in quantum computer algorithms, including both black-box and non-black-box results. It is infeasible to detail all the known quantum algorithms, so a representative sample is given. This includes a summary of the early quantum algorithms, a description of the Abelian Hidden Subgroup algorithms (including Shor's factoring and discrete logarithm algorithms), quantum searching and amplitude amplification, quantum algorithms for simulating quantum mechanical systems, several non-trivial generalizations of the Abelian Hidden Subgroup Problem (and related techniques), the quantum walk paradigm for quantum algorithms, the paradigm of adiabatic algorithms, a family of ``topological'' algorithms, and algorithms for quantum tasks which cannot be done by a classical computer, followed by a discussion.
Transport and Dissipation in Quantum Pumps
J. E. Avron; A. Elgart; G. M. Graf; L. Sadun
2003-05-23
This paper is about adiabatic transport in quantum pumps. The notion of ``energy shift'', a self-adjoint operator dual to the Wigner time delay, plays a role in our approach: It determines the current, the dissipation, the noise and the entropy currents in quantum pumps. We discuss the geometric and topological content of adiabatic transport and show that the mechanism of Thouless and Niu for quantized transport via Chern numbers cannot be realized in quantum pumps where Chern numbers necessarily vanish.
Quantum Simulator for Transport Phenomena in Fluid Flows
A. Mezzacapo; M. Sanz; L. Lamata; I. L. Egusquiza; S. Succi; E. Solano
2015-08-19
Transport phenomena still stand as one of the most challenging problems in computational physics. By exploiting the analogies between Dirac and lattice Boltzmann equations, we develop a quantum simulator based on pseudospin-boson quantum systems, which is suitable for encoding fluid dynamics transport phenomena within a lattice kinetic formalism. It is shown that both the streaming and collision processes of lattice Boltzmann dynamics can be implemented with controlled quantum operations, using a heralded quantum protocol to encode non-unitary scattering processes. The proposed simulator is amenable to realization in controlled quantum platforms, such as ion-trap quantum computers or circuit quantum electrodynamics processors.
Quantum interference within the complex quantum Hamilton-Jacobi formalism
Chia-Chun Chou; Angel S. Sanz; Salvador Miret-Artes; Robert E. Wyatt
2010-05-26
Quantum interference is investigated within the complex quantum Hamilton-Jacobi formalism. As shown in a previous work [Phys. Rev. Lett. 102, 250401 (2009)], complex quantum trajectories display helical wrapping around stagnation tubes and hyperbolic deflection near vortical tubes, these structures being prominent features of quantum caves in space-time Argand plots. Here, we further analyze the divergence and vorticity of the quantum momentum function along streamlines near poles, showing the intricacy of the complex dynamics. Nevertheless, despite this behavior, we show that the appearance of the well-known interference features (on the real axis) can be easily understood in terms of the rotation of the nodal line in the complex plane. This offers a unified description of interference as well as an elegant and practical method to compute the lifetime for interference features, defined in terms of the average wrapping time, i.e., considering such features as a resonant process.
Fresnel-transform's quantum correspondence and quantum optical ABCD Law
Fan Hongyi; Hu Liyun
2007-05-29
Corresponding to Fresnel transform there exists a unitary operator in quantum optics theory, which could be named Fresnel operator (FO). We show that the multiplication rule of FO naturally leads to the quantum optical ABCD law. The canonical operator methods as mapping of ray-transfer ABCD matrix is explicitly shown by FO's normally ordered expansion through the coherent state representation and the technique of integration within an ordered product of operators. We show that time evolution of the damping oscillator embodies the quantum optical ABCD law.
Ronnie Kosloff
2013-05-10
Quantum thermodynamics addresses the emergence of thermodynamical laws from quantum mechanics. The link is based on the intimate connection of quantum thermodynamics with the theory of open quantum systems. Quantum mechanics inserts dynamics into thermodynamics giving a sound foundation to finite-time-thermodynamics. The emergence of the 0-law I-law II-law and III-law of thermodynamics from quantum considerations is presented. The emphasis is on consistence between the two theories which address the same subject from different foundations. We claim that inconsistency is the result of faulty analysis pointing to flaws in approximations.
Continuous Variable Quantum Information Processing
Ulrik L. Andersen; Gerd Leuchs; Christine Silberhorn
2010-08-20
Observables of quantum systems can posses either a discrete or a continuous spectrum. For example, upon measurements of the photon number of a light state, discrete outcomes will result whereas measurements of the light's quadrature amplitudes result in continuous outcomes. If one uses the continuous degree of freedom of a quantum system either for encoding, processing or detecting information, one enters the field of continuous variable (CV) quantum information processing. In this paper we review the basic principles of CV quantum information processing with main focus on recent developments in the field. We will be addressing the three main stages of a quantum informational system; the preparation stage where quantum information is encoded into CVs of coherent states and single photon states, the processing stage where CV information is manipulated to carry out a specified protocol and a detection stage where CV information is measured using homodyne detection or photon counting.
Efficient Networks for Quantum Factoring
David Beckman; Amalavoyal N. Chari; Srikrishna Devabhaktuni; John Preskill
1996-02-21
We consider how to optimize memory use and computation time in operating a quantum computer. In particular, we estimate the number of memory qubits and the number of operations required to perform factorization, using the algorithm suggested by Shor. A $K$-bit number can be factored in time of order $K^3$ using a machine capable of storing $5K+1$ qubits. Evaluation of the modular exponential function (the bottleneck of Shor's algorithm) could be achieved with about $72 K^3$ elementary quantum gates; implementation using a linear ion trap would require about $396 K^3$ laser pulses. A proof-of-principle demonstration of quantum factoring (factorization of 15) could be performed with only 6 trapped ions and 38 laser pulses. Though the ion trap may never be a useful computer, it will be a powerful device for exploring experimentally the properties of entangled quantum states.
Bohmian mechanics contradicts quantum mechanics
Arnold Neumaier
2000-02-16
It is shown that, for a harmonic oscillator in the ground state, Bohmian mechanics and quantum mechanics predict values of opposite sign for certain time correlations. The discrepancy can be explained by the fact that Bohmian mechanics has no natural way to accomodate the Heisenberg picture, since the local expectation values that define the beables of the theory depend on the Heisenberg time being used to define the operators. Relations to measurement are discussed, too, and shown to leave no loophole for claiming that Bohmian mechanics reproduces all predictions of quantum mechanics exactly.
A Description of Quantum Chaos
Kei Inoue; Andrzej Kossakowski; Masanori Ohya
2004-06-30
A measure describing the chaos of a dynamics was introduced by two complexities in information dynamics, and it is called the chaos degree. In particular, the entropic chaos degree has been used to characterized several dynamical maps such that logistis, Baker's, Tinckerbel's in classical or quantum systems. In this paper, we give a new treatment of quantum chaos by defining the entropic chaos degree for quantum transition dynamics, and we prove that every non-chaotic quantum dynamics, e.g., dissipative dynamics, has zero chaos degree. A quantum spin 1/2 system is studied by our chaos degree, and it is shown that this degree well describes the chaotic behavior of the spin system.
Zumbühl, Dominik
Spins in few-electron quantum dots R. Hanson* Center for Spintronics and Quantum Computation these subjects are directly relevant for the fields of quantum information processing and spintronics with single spins i.e., single spintronics . DOI: 10.1103/RevModPhys.79.1217 PACS number s : 73.63.Kv, 03.67.Lx, 85
Experimental Quantum Process Discrimination
Anthony Laing; Terry Rudolph; Jeremy L. O'Brien
2008-07-01
Discrimination between unknown processes chosen from a finite set is experimentally shown to be possible even in the case of non-orthogonal processes. We demonstrate unambiguous deterministic quantum process discrimination (QPD) of non-orthogonal processes using properties of entanglement, additional known unitaries, or higher dimensional systems. Single qubit measurement and unitary processes and multipartite unitaries (where the unitary acts non-separably across two distant locations) acting on photons are discriminated with a confidence of $\\geq97%$ in all cases.
Keith R. Motes; Jonathan P. Olson; Evan J. Rabeaux; Jonathan P. Dowling; S. Jay Olson; Peter P. Rohde
2015-05-04
Quantum number-path entanglement is a resource for super-sensitive quantum metrology and in particular provides for sub-shotnoise or even Heisenberg-limited sensitivity. However, such number-path entanglement has thought to have been resource intensive to create in the first place --- typically requiring either very strong nonlinearities, or nondeterministic preparation schemes with feed-forward, which are difficult to implement. Very recently, arising from the study of quantum random walks with multi-photon walkers, as well as the study of the computational complexity of passive linear optical interferometers fed with single-photon inputs, it has been shown that such passive linear optical devices generate a superexponentially large amount of number-path entanglement. A logical question to ask is whether this entanglement may be exploited for quantum metrology. We answer that question here in the affirmative by showing that a simple, passive, linear-optical interferometer --- fed with only uncorrelated, single-photon inputs, coupled with simple, single-mode, disjoint photodetection --- is capable of significantly beating the shotnoise limit. Our result implies a pathway forward to practical quantum metrology with readily available technology.
Black hole spectroscopy from Loop Quantum Gravity models
Aurelien Barrau; Xiangyu Cao; Karim Noui; Alejandro Perez
2015-04-21
Using Monte Carlo simulations, we compute the integrated emission spectra of black holes in the framework of Loop Quantum Gravity (LQG). The black hole emission rates are governed by the entropy whose value, in recent holographic loop quantum gravity models, was shown to agree at leading order with the Bekenstein-Hawking entropy. Quantum corrections depend on the Barbero-Immirzi parameter $\\gamma$. Starting with black holes of initial horizon area $A \\sim 10^2$ in Planck units, we present the spectra for different values of $\\gamma$. Each spectrum clearly decomposes in two distinct parts: a continuous background which corresponds to the semi-classical stages of the evaporation and a series of discrete peaks which constitutes a signature of the deep quantum structure of the black hole. We show that $\\gamma$ has an effect on both parts that we analyze in details. Finally, we estimate the number of black holes and the instrumental resolution required to experimentally distinguish between the considered models.
Large-amplitude solitons in gravitationally balanced quantum plasmas
Akbari-Moghanjoughi, M.
2014-08-15
Using the quantum fluid model for self-gravitating quantum plasmas with the Bernoulli pseudopotential method and taking into account the relativistic degeneracy effect, it is shown that gravity-induced large-amplitude density rarefaction solitons can exist in gravitationally balanced quantum plasmas. These nonlinear solitons are generated due to the force imbalance between the gravity and the quantum fluid pressure via local density perturbations, similar to that on shallow waters. It is found that both the fluid mass-density and the atomic-number of the constituent ions have significant effect on the amplitude and width of these solitonic profiles. Existence of a large-scale gravity-induced solitonic activities on neutron-star surface, for instance, can be a possible explanation for the recently proposed resonant shattering mechanism [D. Tsang et al., Phys. Rev. Lett. 108, 011102 (2012)] causing the intense short gamma ray burst phenomenon, in which release of ?10{sup 46}–10{sup 47} ergs would be possible from the surface. The resonant shattering of the crust in a neutron star has been previously attributed to the crust-core interface mode and the tidal surface tensions. We believe that current model can be a more natural explanation for the energy liberation by solitonic activities on the neutron star surfaces, without a requirement for external mergers like other neutron stars or black holes for the crustal shatter.
On a realistic interpretation of quantum mechanics
Arnold Neumaier
1999-08-22
The best mathematical arguments against a realistic interpretation of quantum mechanics - that gives definite but partially unknown values to all observables - are analysed and shown to be based on reasoning that is not compelling. This opens the door for an interpretation that, while respecting the indeterministic nature of quantum mechanics, allows to speak of definite values for all observables at any time that are, however, only partially measurable. The analysis also suggests new ways to test the foundations of quantum theory.
Volkmar Putz; Karl Svozil
2015-08-17
We consider ways of conceptualizing, rendering and perceiving quantum music, and quantum art in general. Thereby, we give particular emphasis to its non-classical aspects, such as coherent superposition and entanglement.
Putz, Volkmar
2015-01-01
We consider ways of conceptualizing, rendering and perceiving quantum music, and quantum art in general. Thereby we give particular emphasis to its non-classical aspects, such as coherent superposition and entanglement.
Quaternionic Formulation of Supersymmetric Quantum Mechanics
Seema Rawat; O. P. S. Negi
2007-03-18
Quaternionic formulation of supersymmetric quantum mechanics has been developed consistently in terms of Hamiltonians, superpartner Hamiltonians, and supercharges for free particle and interacting field in one and three dimensions. Supercharges, superpartner Hamiltonians and energy eigenvalues are discussed and it has been shown that the results are consistent with the results of quantum mechanics.
Efficiency of quantum state tomography for qubits
Koichi Yamagata
2011-05-19
The efficiency of quantum state tomography is discussed from the point of view of quantum parameter estimation theory, in which the trace of the weighted covariance is to be minimized. It is shown that tomography is optimal only when a special weight is adopted.
Continuous-Variable Quantum Computing in Optical Time-Frequency Modes using Quantum Memories
Peter C. Humphreys; W. Steven Kolthammer; Joshua Nunn; Marco Barbieri; Animesh Datta; Ian A. Walmsley
2014-11-21
We develop a scheme for time-frequency encoded continuous-variable cluster-state quantum computing using quantum memories. In particular, we propose a method to produce, manipulate and measure 2D cluster states in a single spatial mode by exploiting the intrinsic time-frequency selectivity of Raman quantum memories. Time-frequency encoding enables the scheme to be extremely compact, requiring a number of memories that is a linear function of only the number of different frequencies in which the computational state is encoded, independent of its temporal duration. We therefore show that quantum memories can be a powerful component for scalable photonic quantum information processing architectures.
Certification of Taxpayer Identification Number for Individuals Please check one
Zallen, Richard
Substitute Form W-9 Certification of Taxpayer Identification Number for Individuals Please check: ________________________ Middle: _____________________ Last: _______________________________ 2. U.S. taxpayer identification statements are true, correct, and complete and that: 1. The number shown on this form is my correct taxpayer
I, Quantum Robot: Quantum Mind control on a Quantum Computer
Paola Zizzi
2009-05-28
The logic which describes quantum robots is not orthodox quantum logic, but a deductive calculus which reproduces the quantum tasks (computational processes, and actions) taking into account quantum superposition and quantum entanglement. A way toward the realization of intelligent quantum robots is to adopt a quantum metalanguage to control quantum robots. A physical implementation of a quantum metalanguage might be the use of coherent states in brain signals.
Entanglement Cost of Quantum Channels
Mario Berta; Fernando Brandao; Matthias Christandl; Stephanie Wehner
2012-03-23
The entanglement cost of a quantum channel is the minimal rate at which entanglement (between sender and receiver) is needed in order to simulate many copies of a quantum channel in the presence of free classical communication. In this paper we show how to express this quantity as a regularized optimization of the entanglement formation over states that can be generated between sender and receiver. Our formula is the channel analog of a well-known formula for the entanglement cost of quantum states in terms of the entanglement of formation; and shares a similar relation to the recently shattered hope for additivity. The entanglement cost of a quantum channel can be seen as the analog of the quantum reverse Shannon theorem in the case where free classical communication is allowed. The techniques used in the proof of our result are then also inspired by a recent proof of the quantum reverse Shannon theorem and feature the one-shot formalism for quantum information theory, the post-selection technique for quantum channels as well as von Neumann's minimax theorem. We discuss two applications of our result. First, we are able to link the security in the noisy-storage model to a problem of sending quantum rather than classical information through the adversary's storage device. This not only improves the range of parameters where security can be shown, but also allows us to prove security for storage devices for which no results were known before. Second, our result has consequences for the study of the strong converse quantum capacity. Here, we show that any coding scheme that sends quantum information through a quantum channel at a rate larger than the entanglement cost of the channel has an exponentially small fidelity.
Entanglement Cost of Quantum Channels
Mario Berta; Fernando Brandao; Matthias Christandl; Stephanie Wehner
2015-11-02
The entanglement cost of a quantum channel is the minimal rate at which entanglement (between sender and receiver) is needed in order to simulate many copies of a quantum channel in the presence of free classical communication. In this paper we show how to express this quantity as a regularised optimisation of the entanglement formation over states that can be generated between sender and receiver. Our formula is the channel analog of a well-known formula for the entanglement cost of quantum states in terms of the entanglement of formation; and shares a similar relation to the recently shattered hope for additivity. The entanglement cost of a quantum channel can be seen as the analog of the quantum reverse Shannon theorem in the case where free classical communication is allowed. The techniques used in the proof of our result are then also inspired by a recent proof of the quantum reverse Shannon theorem and feature the one-shot formalism for quantum information theory, the post-selection technique for quantum channels as well as Sion's minimax theorem. We discuss two applications of our result. First, we are able to link the security in the noisy-storage model to a problem of sending quantum rather than classical information through the adversary's storage device. This not only improves the range of parameters where security can be shown, but also allows us to prove security for storage devices for which no results were known before. Second, our result has consequences for the study of the strong converse quantum capacity. Here, we show that any coding scheme that sends quantum information through a quantum channel at a rate larger than the entanglement cost of the channel has an exponentially small fidelity.
Quantum to Classical Transition in a Single-Ion Laser
François Dubin; Carlos Russo; Helena G. Barros; Andreas Stute; Christoph Becher; Piet O. Schmidt; Rainer Blatt
2010-02-18
Stimulated emission of photons from a large number of atoms into the mode of a strong light field is the principle mechanism for lasing in "classical" lasers. The onset of lasing is marked by a threshold which can be characterised by a sharp increase in photon flux as a function of external pumping strength. The same is not necessarily true for the fundamental building block of a laser: a single trapped atom interacting with a single optical radiation mode. It has been shown that such a "quantum" laser can exhibit thresholdless lasing in the regime of strong coupling between atom and radiation field. However, although theoretically predicted, a threshold at the single-atom level could not be experimentally observed so far. Here, we demonstrate and characterise a single-atom laser with and without threshold behaviour by changing the strength of atom-light field coupling. We observe the establishment of a laser threshold through the accumulation of photons in the optical mode even for a mean photon number substantially lower than for the classical case. Furthermore, self-quenching occurs for very strong external pumping and constitutes an intrinsic limitation of single-atom lasers. Moreover, we find that the statistical properties of the emitted light can be adjusted for weak external pumping, from the quantum to the classical domain. Our observations mark an important step towards fundamental understanding of laser operation in the few-atom limit including systems based on semiconductor quantum dots or molecules.
Nicolas Gisin
2015-07-18
Quantum Communication is the art of transferring an unknown quantum state from one location, Alice, to a distant one, Bob. This is a non-trivial task because of the quantum no-cloning theorem which prevents one from merely using only classical means.
Static Quantum Games Revisited
Marcin Markiewicz; Adrian Kosowski; Tomasz Tylec; Jaroslaw Pykacz; Cyril Gavoille
2010-03-23
The so called \\emph{quantum game theory} has recently been proclaimed as one of the new branches in the development of both quantum information theory and game theory. However, the notion of a quantum game itself has never been strictly defined, which has led to a lot of conceptual confusion among different authors. In this paper we introduce a new conceptual framework of a \\emph{scenario} and an \\emph{implementation} of a game. It is shown that the procedures of "quantization" of games proposed in the literature lead in fact to several different games which can be defined within the same scenario, but apart from this they may have nothing in common with the original game. Within the framework we put forward, a lot of conceptual misunderstandings that have arisen around "quantum games" can be stated clearly and resolved uniquely. In particular, the proclaimed essential role of entanglement in several static "quantum games", and their connection with Bell inequalities, is disproved.
STABILITY OF ULTRAVIOLETCUTOFF QUANTUM ELECTRODYNAMICS
, the contribution of the nuclear Zeeman energies to the ground state energy of the system is much smaller than that the quantumÂmechanical ground state energy of a system consisting of an arbitrary number, M , of static nuclei/2 and a bare gyroÂmagnetic factor g = 2, an arbitrary number, M , of nuclei of nuclear charge Å¸ Ze, for some
Shepelyansky, Dima
Applications of quantum chaos to realistic quantum computations and sound treatment on quantum speech and sound of complex quantum wavefunctions. Keywords: Quantum computers, quantum chaos
Albert Schwarz
2014-08-16
One says that a pair (P,Q) of ordinary differential operators specify a quantum curve if [P,Q]=const. If a pair of difference operators (K,L) obey the relation KL=const LK we say that they specify a discrete quantum curve. This terminology is prompted by well known results about commuting differential and difference operators, relating pairs of such operators with pairs of meromorphic functions on algebraic curves obeying some conditions. The goal of this paper is to study the moduli spaces of quantum curves. We will show how to quantize a pair of commuting differential or difference operators (i.e. to construct the corresponding quantum curve or discrete quantum curve). The KP-hierarchy acts on the moduli space of quantum curves; we prove that similarly the discrete KP-hierarchy acts on the moduli space of discrete quantum curves.
Dhananjay P. Mehendale
2006-05-24
In this paper we define new numbers called the Neo-Ramsay numbers. We show that these numbers are in fact equal to the Ramsay numbers. Neo-Ramsey numbers are easy to compute and for finding them it is not necessary to check all possible graphs but enough to check only special kind of graphs having a well-defined adjacency pattern.
Quantum information science and complex quantum systems
Michael A. Nielsen
2002-10-01
What makes quantum information science a science? This paper explores the idea that quantum information science may offer a powerful approach to the study of complex quantum systems.
Wunderlich, Christof
radiation in the radiofrequency or microwave regime. DOI: 10.1103/PhysRevLett.87.257904 PACS numbers: 03 Logic Using Long-Wavelength Radiation Florian Mintert1 and Christof Wunderlich2,* 1 I. Institut fÃ¼r radiation; the atom with mass m is trapped in a harmonic potential characterized by angular frequency vl
Argyris Nicolaidis
2012-11-09
We suggest that the inner syntax of Quantum Mechanics is relational logic, a form of logic developed by C. S. Peirce during the years 1870 - 1880. The Peircean logic has the structure of category theory, with relation serving as an arrow (or morphism). At the core of the relational logical system is the law of composition of relations. This law leads to the fundamental quantum rule of probability as the square of an amplitude. Our study of a simple discrete model, extended to the continuum, indicates that a finite number of degrees of freedom can live in phase space. This "granularity" of phase space is determined by Planck's constant h. We indicate also the broader philosophical ramifications of a relational quantum mechanics.
Quantum informatics with plasmonic metamaterials
Ali A. Kamli; Sergey A. Moiseev; Barry C. Sanders
2010-08-07
Surface polaritons at a meta-material interface are proposed as qubits. The SP fields are shown to have low losses, subwavelength confinement and can demonstrate very small modal volume. These important properties are used to demonstatre interesting applications in quantum information, i.e., coherent control of weak fields and large Kerr nonlinearity at the low photon level.
Quantum Fourier transform and tomographic Renyi entropic inequalities
M. A. Man'ko; V. I. Man'ko
2009-02-25
Renyi entropy associated with spin tomograms of quantum states is shown to obey to new inequalities containing the dependence on quantum Fourier transform. The limiting inequality for the von Neumann entropy of spin quantum states and a new kind of entropy associated with quantum Fourier transform are obtained. Possible connections with subadditivity and strong subadditivity conditions for tomographic entropies and von Neumann entropies are discussed.
Emergence of classical behavior from the quantum spin
M. Radonjic; S. Prvanovic; N. Buric
2012-02-09
Classical Hamiltonian system of a point moving on a sphere of fixed radius is shown to emerge from the constrained evolution of quantum spin. The constrained quantum evolution corresponds to an appropriate coarse-graining of the quantum states into equivalence classes, and forces the equivalence classes to evolve as single units representing the classical states. The coarse-grained quantum spin with the constrained evolution in the limit of the large spin becomes indistinguishable from the classical system.
Quantum walks and quantum search on graphene lattices
Iain Foulger; Sven Gnutzmann; Gregor Tanner
2015-01-29
Quantum walks have been very successful in the development of search algorithms in quantum information, in particular in the development of spatial search algorithms. However, the construction of continuous-time quantum search algorithms in two-dimensional lattices has proved difficult, requiring additional degrees of freedom. Here, we demonstrate that continuous-time quantum walk search is possible in two-dimensions by changing the search topology to a graphene lattice, utilising the Dirac point in the energy spectrum. This is made possible by making a change to standard methods of marking a particular site in the lattice. Various ways of marking a site are shown to result in successful search protocols. We further establish that the search can be adapted to transfer probability amplitude across the lattice between specific lattice sites thus establishing a line of communication between these sites.
Quantum walks and quantum search on graphene lattices
Iain Foulger; Sven Gnutzmann; Gregor Tanner
2015-07-01
Quantum walks have been very successful in the development of search algorithms in quantum information, in particular in the development of spatial search algorithms. However, the construction of continuous-time quantum search algorithms in two-dimensional lattices has proved difficult, requiring additional degrees of freedom. Here, we demonstrate that continuous-time quantum walk search is possible in two-dimensions by changing the search topology to a graphene lattice, utilising the Dirac point in the energy spectrum. This is made possible by making a change to standard methods of marking a particular site in the lattice. Various ways of marking a site are shown to result in successful search protocols. We further establish that the search can be adapted to transfer probability amplitude across the lattice between specific lattice sites thus establishing a line of communication between these sites.
Some Aspects of Planck Scale Quantum Optics
Kourosh Nozari
2005-08-11
This paper considers the effects of gravitational induced uncertainty on some well-known quantum optics issues. First we will show that gravitational effects at quantum level destroy the notion of harmonic oscillations. Then it will be shown that, although it is possible(at least in principle) to have complete coherency and vanishing broadening in usual quantum optics, gravitational induced uncertainty destroys complete coherency and it is impossible to have a monochromatic ray. We will show that there is an additional wave packet broadening due to quantum gravitational effects.
Quantum potential energy as concealed motion
Peter Holland
2014-11-13
It is known that the Schroedinger equation may be derived from a hydrodynamic model in which the Lagrangian position coordinates of a continuum of particles represent the quantum state. Using Routh\\s method of ignorable coordinates it is shown that the quantum potential energy of particle interaction that represents quantum effects in this model may be regarded as the kinetic energy of additional concealed freedoms. The method brings an alternative perspective to Planck\\s constant, which plays the role of a hidden variable, and to the canonical quantization procedure, since what is termed kinetic energy in quantum mechanics may be regarded literally as energy due to motion.
1 -Routing Number 2 -Account Number
Chen, Yiling
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Sparse Quantum Codes from Quantum Circuits
Dave Bacon; Steven T. Flammia; Aram W. Harrow; Jonathan Shi
2015-07-10
We describe a general method for turning quantum circuits into sparse quantum subsystem codes. Using this prescription, we can map an arbitrary stabilizer code into a new subsystem code with the same distance and number of encoded qubits but where all the generators have constant weight, at the cost of adding some ancilla qubits. With an additional overhead of ancilla qubits, the new code can also be made spatially local. Applying our construction to certain concatenated stabilizer codes yields families of subsystem codes with constant-weight generators and with minimum distance $d = n^{1-\\varepsilon}$, where $\\varepsilon = O(1/\\sqrt{\\log n})$. For spatially local codes in $D$ dimensions we nearly saturate a bound due to Bravyi and Terhal and achieve $d = n^{1-\\varepsilon-1/D}$. Previously the best code distance achievable with constant-weight generators in any dimension, due to Freedman, Meyer and Luo, was $O(\\sqrt{n\\log n})$ for a stabilizer code.
Weedbrook, Christian
The science of quantum information has arisen over the last two decades centered on the manipulation of individual quanta of information, known as quantum bits or qubits. Quantum computers, quantum cryptography, and quantum ...
Quantum Differential and Linear Cryptanalysis
Marc Kaplan; Gaëtan Leurent; Anthony Leverrier; María Naya-Plasencia
2015-10-20
Quantum computers, that may become available one day, will impact many scientific fields. Cryptography is certainly one of them since many asymmetric primitives would become insecure against an adversary with quantum capabilities. Cryptographers are already anticipating this threat by proposing and studying a number of potentially quantum-safe alternatives for those primitives. On the other hand, the situation of symmetric primitives which seem less vulnerable against quantum computing, has received much less attention. We need to prepare symmetric cryptography for the eventual arrival of the post-quantum world, as it is done with other cryptography branches. Cryptanalysis and security analysis are the only proper way to evaluate the security of symmetric primitives: our trust in specific ciphers relies on their ability to resist all known cryptanalysis tools. This requires a proper investigation of the toolkit of quantum cryptanalysis, that might include radically new attacks. This toolkit has not been much developed so far. In this paper, we study how some of the main cryptanalytic attacks behave in the post-quantum world. More specifically, we consider here quantum versions of differential and linear cryptanalysis. While running Grover's search algorithm on a quantum computer brings a quadratic speedup for brute-force attacks, we show that the situation is more subtle when considering specific cryptanalysis techniques. In particular, we give the quantum version of various classes of differential and linear attacks and show that the best attacks in the classical world do not necessarily lead to the best quantum ones. Some non-intuitive examples of application on ciphers LAC and KLEIN are provided.
A reconfigurable spintronic device for quantum and classical logic
Bhowmik, Debanjan; Sarkar, Angik; Bhattacharyya, Tarun Kanti
2010-01-01
Quantum superposition and entanglement of physical states can be harnessed to solve some problems which are intractable on a classical computer implementing binary logic. Several algorithms have been proposed to utilize the quantum nature of physical states and solve important problems. For example, Shor's quantum algorithm is extremely important in the field of cryptography since it factors large numbers exponentially faster than any known classical algorithm. Another celebrated example is the Grovers quantum algorithm. These algorithms can only be implemented on a quantum computer which operates on quantum bits (qubits). Rudimentary implementations of quantum processor have already been achieved through linear optical components, ion traps, NMR etc. However demonstration of a solid state quantum processor had been elusive till DiCarlo et al demonstrated two qubit algorithms in superconducting quantum processor. Though this has been a significant step, scalable semiconductor based room temperature quantum co...
Sai Vinjanampathy; Janet Anders
2015-08-25
Quantum thermodynamics is an emerging research field aiming to extend standard thermodynamics and non-equilibrium statistical physics to ensembles of sizes well below the thermodynamic limit, in non-equilibrium situations, and with the full inclusion of quantum effects. Fuelled by experimental advances and the potential of future nanoscale applications this research effort is pursued by scientists with different backgrounds, including statistical physics, many-body theory, mesoscopic physics and quantum information theory, who bring various tools and methods to the field. A multitude of theoretical questions are being addressed ranging from issues of thermalisation of quantum systems and various definitions of "work", to the efficiency and power of quantum engines. This overview provides a perspective on a selection of these current trends accessible to postgraduate students and researchers alike.
Quantum Secret Sharing and Random Hopping; Using single states instead of entanglement
Vahid Karimipour; Marzieh Asoudeh
2015-07-18
Quantum protocols for secret sharing usually rely on multi-party entanglement which with present technology is very difficult to achieve. Recently it has been shown that sequential manipulation and communication of a single $d-$ level state can do the same task of secret sharing between $N$ parties, hence alleviating the need for entanglement. However the suggested protocol which is based on using mutually unbiased bases, works only when $d$ is a prime number. We propose a new sequential protocol which is valid for any $d$.
Algorithmic cooling and scalable NMR quantum computers
Mor, Tal
Algorithmic cooling and scalable NMR quantum computers P. Oscar Boykin*, Tal MorÂ§ , Vwani cooling (via polarization heat bath)--a powerful method for obtaining a large number of highly polarized (quantum) bits, algorithmic cooling cleans dirty bits beyond the Shannon's bound on data compression
Entropy of quantum channel in the theory of quantum information
Wojciech Roga
2011-10-03
Quantum channels, also called quantum operations, are linear, trace preserving and completely positive transformations in the space of quantum states. Such operations describe discrete time evolution of an open quantum system interacting with an environment. The thesis contains an analysis of properties of quantum channels and different entropies used to quantify the decoherence introduced into the system by a given operation. Part I of the thesis provides a general introduction to the subject. In Part II, the action of a quantum channel is treated as a process of preparation of a quantum ensemble. The Holevo information associated with this ensemble is shown to be bounded by the entropy exchanged during the preparation process between the initial state and the environment. A relation between the Holevo information and the entropy of an auxiliary matrix consisting of square root fidelities between the elements of the ensemble is proved in some special cases. Weaker bounds on the Holevo information are also established. The entropy of a channel, also called the map entropy, is defined as the entropy of the state corresponding to the channel by the Jamiolkowski isomorphism. In Part III of the thesis, the additivity of the entropy of a channel is proved. The minimal output entropy, which is difficult to compute, is estimated by an entropy of a channel which is much easier to obtain. A class of quantum channels is specified, for which additivity of channel capacity is conjectured. The last part of the thesis contains characterization of Davies channels, which correspond to an interaction of a state with a thermal reservoir in the week coupling limit, under the condition of quantum detailed balance and independence of rotational and dissipative evolutions. The Davies channels are characterized for one-qubit and one-qutrit systems.
Autonomous Perceptron Neural Network Inspired from Quantum computing
M. Zidan; A. Sagheer; N. Metwally
2015-10-02
Recently with the rapid development of technology, there are a lot of applications require to achieve low-cost learning in order to accomplish inexpensive computation. However the known computational power of classical artificial neural networks (CANN), they are not capable to provide low-cost learning due to many reasons such as linearity, complexity of architecture, etc. In contrast, quantum neural networks (QNN) may be representing a good computational alternate to CANN, based on the computational power of quantum bit (qubit) over the classical bit. In this paper, a new algorithm of quantum perceptron neural network based only on one neuron is introduced to overcome some limitations of the classical perceptron neural networks. The proposed algorithm is capable to construct its own set of activation operators that enough to accomplish the learning process in a limited number of iterations and, consequently, reduces the cost of computation. For evaluation purpose, we utilize the proposed algorithm to solve five problems using real and artificial data. It is shown throughout the paper that promising results are provided and compared favorably with other reported algorithms
From the Academy Random matrices and quantum chaos
Marklof, Jens
From the Academy Random matrices and quantum chaos Thomas Kriecherbauer*, Jens Marklof appearances of random matrices, namely in the theory of quantum chaos and in the theory of prime numbers, in fact, are not only used to describe statistical properties of physical systems (e.g., in quantum chaos
Set discrimination of quantum states Shengyu Zhang* and Mingsheng Ying
Zhang, Shengyu
Set discrimination of quantum states Shengyu Zhang* and Mingsheng Ying State Key Laboratory discrimination, which is an interesting extension of quantum state discrimina- tion. A state is secretly chosen from a number of quantum states, which are partitioned into some disjoint sets. A set discrimination
Quantum hoop conjecture and a natural cutoff for vacuum energy
Yang, Rong-Jia
2015-01-01
We propose here a quantum hoop conjecture which states: the de Broglie wavelength of a quantum system can not be infinitely small, otherwise it will collapse into a quantum black hole. Based on this conjecture, we find an upper bound for the wave number of a particle, which offers a natural cutoff for the vacuum energy.
Shape invariance and the exactness of quantum Hamilton-Jacobi formalism
Charles Cherqui; Yevgeny Binder; Asim Gangopadhyaya
2007-09-25
Quantum Hamilton-Jacobi Theory and supersymmetric quantum mechanics (SUSYQM) are two parallel methods to determine the spectra of a quantum mechanical systems without solving the Schr\\"odinger equation. It was recently shown that the shape invariance, which is an integrability condition in SUSYQM formalism, can be utilized to develop an iterative algorithm to determine the quantum momentum functions. In this paper, we show that shape invariance also suffices to determine the eigenvalues in Quantum Hamilton-Jacobi Theory.
Geometry and symmetry of quantum and classical-quantum variational principles
Esther Bonet Luz; Cesare Tronci
2015-01-28
This paper presents the geometric setting of quantum variational principles and extends it to comprise the interaction between classical and quantum degrees of freedom. Euler-Poincar\\'e reduction theory is applied to the Schr\\"odinger, Heisenberg and Wigner-Moyal dynamics of pure states. This construction leads to new variational principles for the description of mixed quantum states. The corresponding momentum map properties are presented as they arise from the underlying unitary symmetries. Finally, certain semidirect-product group structures are shown to produce new variational principles for Dirac's interaction picture and the equations of hybrid classical-quantum dynamics.
Two-particle quantum transmission
Ron Folman
2012-11-25
Two-photon interference is a fundamental phenomenon in quantum mechanics and stands at the base of numerous experimental observations. Here another manifestation of this phenomenon is described, taking place at a Y junction. Specifically it is shown how the r^2+t^2 term which is behind previous observations of two-photon interference, may give rise to different states at a beam-splitter and different two-particle transmission coefficients at a Y junction. Different from previous descriptions of quantum transmission based on one-particle physics, the enhanced transmission described here is due to two-particle physics.
Quantum Indeterminacy of Cosmic Systems
Hogan, Craig J.
2013-12-30
It is shown that quantum uncertainty of motion in systems controlled mainly by gravity generally grows with orbital timescale $H^{-1}$, and dominates classical motion for trajectories separated by distances less than $\\approx H^{-3/5}$ in Planck units. For example, the cosmological metric today becomes indeterminate at macroscopic separations, $H_0^{-3/5}\\approx 60$ meters. Estimates suggest that entangled non-localized quantum states of geometry and matter may significantly affect fluctuations during inflation, and connect the scale of dark energy to that of strong interactions.
Quantum Coding with Finite Resources
Marco Tomamichel; Mario Berta; Joseph M. Renes
2015-05-28
The quantum capacity of a memoryless channel is often used as a single figure of merit to characterize its ability to transmit quantum information coherently. The capacity determines the maximal rate at which we can code reliably over asymptotically many uses of the channel. We argue that this asymptotic treatment is insufficient to the point of being irrelevant in the quantum setting where decoherence severely limits our ability to manipulate large quantum systems in the encoder and decoder. For all practical purposes we should instead focus on the trade-off between three parameters: the rate of the code, the number of coherent uses of the channel, and the fidelity of the transmission. The aim is then to specify the region determined by allowed combinations of these parameters. Towards this goal, we find approximate and exact characterizations of the region of allowed triplets for the qubit dephasing channel and for the erasure channel with classical post-processing assistance. In each case the region is parametrized by a second channel parameter, the quantum channel dispersion. In the process we also develop several general inner (achievable) and outer (converse) bounds on the coding region that are valid for all finite-dimensional quantum channels and can be computed efficiently. Applied to the depolarizing channel, this allows us to determine a lower bound on the number of coherent uses of the channel necessary to witness super-additivity of the coherent information.
Quantum technology and its applications
Boshier, Malcolm; Berkeland, Dana; Govindan, Tr; Abo - Shaeer, Jamil
2010-12-10
Quantum states of matter can be exploited as high performance sensors for measuring time, gravity, rotation, and electromagnetic fields, and quantum states of light provide powerful new tools for imaging and communication. Much attention is being paid to the ultimate limits of this quantum technology. For example, it has already been shown that exotic quantum states can be used to measure or image with higher precision or higher resolution or lower radiated power than any conventional technologies, and proof-of-principle experiments demonstrating measurement precision below the standard quantum limit (shot noise) are just starting to appear. However, quantum technologies have another powerful advantage beyond pure sensing performance that may turn out to be more important in practical applications: the potential for building devices with lower size/weight/power (SWaP) and cost requirements than existing instruments. The organizers of Quantum Technology Applications Workshop (QTAW) have several goals: (1) Bring together sponsors, researchers, engineers and end users to help build a stronger quantum technology community; (2) Identify how quantum systems might improve the performance of practical devices in the near- to mid-term; and (3) Identify applications for which more long term investment is necessary to realize improved performance for realistic applications. To realize these goals, the QTAW II workshop included fifty scientists, engineers, managers and sponsors from academia, national laboratories, government and the private-sector. The agenda included twelve presentations, a panel discussion, several breaks for informal exchanges, and a written survey of participants. Topics included photon sources, optics and detectors, squeezed light, matter waves, atomic clocks and atom magnetometry. Corresponding applications included communication, imaging, optical interferometry, navigation, gravimetry, geodesy, biomagnetism, and explosives detection. Participants considered the physics and engineering of quantum and conventional technologies, and how quantum techniques could (or could not) overcome limitations of conventional systems. They identified several auxiliary technologies that needed to be further developed in order to make quantum technology more accessible. Much of the discussion also focused on specific applications of quantum technology and how to push the technology into broader communities, which would in turn identify new uses of the technology. Since our main interest is practical improvement of devices and techniques, we take a liberal definition of 'quantum technology': a system that utilizes preparation and measurement of a well-defined coherent quantum state. This nomenclature encompasses features broader than entanglement, squeezing or quantum correlations, which are often more difficult to utilize outside of a laboratory environment. Still, some applications discussed in the workshop do take advantage of these 'quantum-enhanced' features. They build on the more established quantum technologies that are amenable to manipulation at the quantum level, such as atom magnetometers and atomic clocks. Understanding and developing those technologies through traditional engineering will clarify where quantum-enhanced features can be used most effectively, in addition to providing end users with improved devices in the near-term.
Shannon Capacity Ramsey Numbers
Radziszowski, Stanislaw P.
Shannon Capacity Ramsey Numbers Old links between Shannon and Ramsey New links between Shannon and Ramsey Bounds on Shannon Capacity and Ramsey Numbers from Product of Graphs Xiaodong Xu1 Stanislaw Institute of Technology, NY, USA March 2014 1/24 #12;Shannon Capacity Ramsey Numbers Old links between
Strongly Intensive Measures for Particle Number Fluctuations: Effects of Hadronic Resonances
Viktor V. Begun; Mark I. Gorenstein; Katarzyna Grebieszkow
2015-05-15
Strongly intensive measures $\\Delta$ and $\\Sigma$ are used to study event-by-event fluctuations of hadron multiplicities in nucleus-nucleus collisions. The effects of resonance decays are investigated within statistical model and relativistic transport model. Two specific examples are considered: resonance decays to two positively charged particles (e.g., $\\Delta^{++}\\rightarrow p+ \\pi^+$) and to $\\pi^+\\pi^-$-pairs. (e.g., $\\rho^0\\rightarrow \\pi^-+\\pi^+$). It is shown that resonance abundances at the chemical freeze-out can be estimated by measuring the fluctuations of the number of stable hadrons. These model results are compared to the full hadron-resonance gas analysis within both the grand canonical and canonical ensemble. The ultra-relativistic quantum molecular dynamics (UrQMD) model of nucleus-nucleus collisions is used to illustrate the role of global charge conservation, centrality selection, and limited experimental acceptance.
Unpredictability and the transmission of numbers
Myers, John M
2015-01-01
Curiously overlooked in physics is its dependence on the transmission of numbers. For example the transmission of numerical clock readings is implicit in the concept of a coordinate system. The transmission of numbers and other logical distinctions is often achieved over a computer-mediated communications network in the face of an unpredictable environment. By unpredictable we mean something stronger than the spread of probabilities over given possible outcomes, namely an opening to unforeseeable possibilities. Unpredictability, until now overlooked in theoretical physics, makes the transmission of numbers interesting. Based on recent proofs within quantum theory that provide a theoretical foundation to unpredictability, here we show how regularities in physics rest on a background of channels over which numbers are transmitted. As is known to engineers of digital communications, numerical transmissions depend on coordination reminiscent of the cycle of throwing and catching by players tossing a ball back and...
Frank Steiner
1994-02-07
A short historical overview is given on the development of our knowledge of complex dynamical systems with special emphasis on ergodicity and chaos, and on the semiclassical quantization of integrable and chaotic systems. The general trace formula is discussed as a sound mathematical basis for the semiclassical quantization of chaos. Two conjectures are presented on the basis of which it is argued that there are unique fluctuation properties in quantum mechanics which are universal and, in a well defined sense, maximally random if the corresponding classical system is strongly chaotic. These properties constitute the quantum mechanical analogue of the phenomenon of chaos in classical mechanics. Thus quantum chaos has been found.
Physicalism versus quantum mechanics
Stapp, Henry P; Theoretical Physics Group; Physics Division
2009-01-01
Foundations of Quantum Mechanics. (Princeton UniversityMind, Matter, and Quantum Mechanics, (Springer, Berlin & NewMindful Universe: Quantum Mechanics and the Participating
Bernd Fröhlich; James F. Dynes; Marco Lucamarini; Andrew W. Sharpe; Zhiliang Yuan; Andrew J. Shields
2014-09-02
The theoretically proven security of quantum key distribution (QKD) could revolutionise how information exchange is protected in the future. Several field tests of QKD have proven it to be a reliable technology for cryptographic key exchange and have demonstrated nodal networks of point-to-point links. However, so far no convincing answer has been given to the question of how to extend the scope of QKD beyond niche applications in dedicated high security networks. Here we show that adopting simple and cost-effective telecommunication technologies to form a quantum access network can greatly expand the number of users in quantum networks and therefore vastly broaden their appeal. We are able to demonstrate that a high-speed single-photon detector positioned at a network node can be shared between up to 64 users for exchanging secret keys with the node, thereby significantly reducing the hardware requirements for each user added to the network. This point-to-multipoint architecture removes one of the main obstacles restricting the widespread application of QKD. It presents a viable method for realising multi-user QKD networks with resource efficiency and brings QKD closer to becoming the first widespread technology based on quantum physics.
Quantum Coherence and Its Distribution
Asutosh Kumar
2015-08-04
Quantum coherence is the yield of the superposition principle. Recently, it has been theorized as a quantum resource, and is the premise of quantum correlations in multipartite systems. However, coherence is degraded by environmental interactions. It is therefore natural to study the coherence content and its distribution in a multipartite quantum system. In this work, we show analytically as well as numerically the reciprocity between coherence and mixedness of a quantum state. It appears that this trade-off is a general feature rather being exotic. We also study the distribution of coherence in multipartite systems and prove several interesting results. Numerical investigation unravels the fact that the percent of quantum states satisfying the additivity relation of coherence increases with increasing number of parties, the rank of quantum state and raising the power of coherence measure under investigation. We also study distribution of coherence in X states. We further show that for Dicke states, while the normalized measures of coherence violate the additivity relation, the unnormalized ones do satisfy the same.
Semi-Poisson statistics in quantum chaos
Antonio M. Garcia-Garcia; Jiao Wang
2006-05-01
We investigate the quantum properties of a non-random Hamiltonian with a step-like singularity. It is shown that the eigenfunctions are multifractals and, in a certain range of parameters, the level statistics is described exactly by Semi-Poisson statistics (SP) typical of pseudo-integrable systems. It is also shown that our results are universal; namely, they depend exclusively on the presence of the step-like singularity and are not modified by smooth perturbations of the potential or the addition of a magnetic flux. Although the quantum properties of our system are similar to those of a disordered conductor at the Anderson transition, we report important quantitative differences in both the level statistics and the multifractal dimensions controlling the transition. Finally the study of quantum transport properties suggests that the classical singularity induces quantum anomalous diffusion. We discuss how these findings may be experimentally corroborated by using ultra cold atoms techniques.
Giovannetti, Vittorio
We give a consistent quantum description of time, based on Page and Wootters’s conditional probabilities mechanism, which overcomes the criticisms that were raised against similar previous proposals. In particular we show ...
Controlled quantum-state transfer in a spin chain
Gong, Jiangbin [Department of Physics and Center for Computational Science and Engineering, National University of Singapore, 117542 (Singapore); Brumer, Paul [Chemical Physics Theory Group and Center for Quantum Information and Quantum Control, University of Toronto, Toronto M5S 3H6 (Canada)
2007-03-15
Control of the transfer of quantum information encoded in quantum wave packets moving along a spin chain is demonstrated. Specifically, based on a relationship with control in a paradigm of quantum chaos, it is shown that wave packets with slow dispersion can automatically emerge from a class of initial superposition states involving only a few spins, and that arbitrary unspecified traveling wave packets can be nondestructively stopped and later relaunched with perfection. The results establish an interesting application of quantum chaos studies in quantum information science.
Michael Mazilu
2015-08-06
The electromagnetic momentum transferred transfered to scattering particles is proportional to the intensity of the incident fields, however, the momentum of single photons ($\\hbar k$) does not naturally appear in these classical expressions. Here, we discuss an alternative to Maxwell's stress tensor that renders the classical electromagnetic field momentum compatible to the quantum mechanical one. This is achieved through the introduction of the quantum conversion which allows the transformation, including units, of the classical fields to wave-function equivalent fields.
Ludwig-Maximilians-Universität, München
of Two Quantum Dots Embedded in an Aharonov-Bohm Interferometer A. W. Holleitner,1,* C. R. Decker,1 H quantum dots. In an intermediate coupling regime we study molecular states of the double dot and extract focus on coherently coupled states within the double quantum dot, first evidence of which has been found
Finite size scaling for quantum criticality using the finite-element method
Edwin Antillon; Birgit Wehefritz-Kaufmann; Sabre Kais
2012-03-08
Finite size scaling for the Schr\\"{o}dinger equation is a systematic approach to calculate the quantum critical parameters for a given Hamiltonian. This approach has been shown to give very accurate results for critical parameters by using a systematic expansion with global basis-type functions. Recently, the finite element method was shown to be a powerful numerical method for ab initio electronic structure calculations with a variable real-space resolution. In this work, we demonstrate how to obtain quantum critical parameters by combining the finite element method (FEM) with finite size scaling (FSS) using different ab initio approximations and exact formulations. The critical parameters could be atomic nuclear charges, internuclear distances, electron density, disorder, lattice structure, and external fields for stability of atomic, molecular systems and quantum phase transitions of extended systems. To illustrate the effectiveness of this approach we provide detailed calculations of applying FEM to approximate solutions for the two-electron atom with varying nuclear charge; these include Hartree-Fock, density functional theory under the local density approximation, and an "exact"' formulation using FEM. We then use the FSS approach to determine its critical nuclear charge for stability; here, the size of the system is related to the number of elements used in the calculations. Results prove to be in good agreement with previous Slater-basis set calculations and demonstrate that it is possible to combine finite size scaling with the finite-element method by using ab initio calculations to obtain quantum critical parameters. The combined approach provides a promising first-principles approach to describe quantum phase transitions for materials and extended systems.
Quantum heuristic algorithm for traveling salesman problem
Jeongho Bang; Seokwon Yoo; James Lim; Junghee Ryu; Changhyoup Lee; Jinhyoung Lee
2012-11-06
We propose a quantum heuristic algorithm to solve a traveling salesman problem by generalizing Grover search. Sufficient conditions are derived to greatly enhance the probability of finding the tours with extremal costs, reaching almost to unity and they are shown characterized by statistical properties of tour costs. In particular for a Gaussian distribution of the tours along the cost we show that the quantum algorithm exhibits the quadratic speedup of its classical counterpart, similarly to Grover search.
How detrimental is decoherence in adiabatic quantum computation?
Albash, Tameem
2015-01-01
Recent experiments with increasingly larger numbers of qubits have sparked renewed interest in adiabatic quantum computation, and in particular quantum annealing. A central question that is repeatedly asked is whether quantum features of the evolution can survive over the long time-scales used for quantum annealing relative to standard measures of the decoherence time. We reconsider the role of decoherence in adiabatic quantum computation and quantum annealing using the adiabatic quantum master equation formalism. We restrict ourselves to the weak-coupling and singular-coupling limits, which correspond to decoherence in the energy eigenbasis and in the computational basis, respectively. We demonstrate that decoherence in the instantaneous energy eigenbasis does not necessarily detrimentally affect adiabatic quantum computation, and in particular that a short single-qubit $T_2$ time need not imply adverse consequences for the success of the quantum adiabatic algorithm. We further demonstrate that boundary canc...
PHYSICAL REVIEW E 83, 066216 (2011) "Weak quantum chaos" and its resistor network modeling
Cohen, Doron
2011-01-01
PHYSICAL REVIEW E 83, 066216 (2011) "Weak quantum chaos" and its resistor network modeling number(s): 05.45.Mt, 03.65.-w, 73.23.-b I. INTRODUCTION So-called quantum chaos is the study of quantized. This is the case if we have weak quantum chaos (WQC) circumstances, in which the traditional RMT modeling does
Min Liang; Li Yang
2012-05-10
Public-key cryptosystems for quantum messages are considered from two aspects: public-key encryption and public-key authentication. Firstly, we propose a general construction of quantum public-key encryption scheme, and then construct an information-theoretic secure instance. Then, we propose a quantum public-key authentication scheme, which can protect the integrity of quantum messages. This scheme can both encrypt and authenticate quantum messages. It is information-theoretic secure with regard to encryption, and the success probability of tampering decreases exponentially with the security parameter with regard to authentication. Compared with classical public-key cryptosystems, one private-key in our schemes corresponds to an exponential number of public-keys, and every quantum public-key used by the sender is an unknown quantum state to the sender.
Liang, Min
2012-01-01
Public-key cryptosystems for quantum messages are considered from two aspects: public-key encryption and public-key authentication. Firstly, we propose a general construction of quantum public-key encryption scheme, and then construct an information-theoretic secure instance. Then, we propose a quantum public-key authentication scheme, which can protect the integrity of quantum messages. This scheme can both encrypt and authenticate quantum messages. It is information-theoretic secure with regard to encryption, and the success probability of tampering decreases exponentially with the security parameter with regard to authentication. Compared with classical public-key cryptosystems, one private-key in our schemes corresponds to an exponential number of public-keys, and every quantum public-key used by the sender is an unknown quantum state to the sender.
Dorje C. Brody; Lane P. Hughston
2014-11-17
A model for a quantum heat bath is introduced. When the bath molecules have finitely many degrees of freedom, it is shown that the assumption that the molecules are weakly interacting is sufficient to enable one to derive the canonical distribution for the energy of a small system immersed in the bath. While the specific form of the bath temperature, for which we provide an explicit formula, depends on (i) spectral properties of the bath molecules, and (ii) the choice of probability measure on the state space of the bath, we are in all cases able to establish the existence of a strictly positive lower bound on the temperature of the bath. The results can be used to test the merits of different hypotheses for the equilibrium states of quantum systems. Two examples of physically plausible choices for the probability measure on the state space of a quantum heat bath are considered in detail, and the associated lower bounds on the temperature of the bath are worked out.
Sandia Energy - Quantum Optics
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Quantum Optics Home Energy Research EFRCs Solid-State Lighting Science EFRC Quantum Optics Quantum OpticsTara Camacho-Lopez2015-03-30T16:37:03+00:00 Quantum Optics with a Single...
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2014-12-03
Dec 3, 2014 ... TBA, Rachel Davis ... September 26, Rachel Davis .... Dessins d'Enfants · Indiana Pi Bill · Notes and Publications · Number Theory Seminar ...
Electrical resistivity as quantum chaos
Laughlin, R.B.
1987-08-01
The physics of quantum transport is re-examined as a problem in quantum chaos. It is proposed that the ''random potential'' in which electrons in dirty metals move is not random at all, but rather any potential inducing the electron motion to be chaotic. The Liapunov characteristic exponent of classical electron motion in this potential is identified with the collision rate l/tau appearing in Ohm's law. A field theory for chaotic systems, analogous to that used to describe dirty metals, is developed and used to investigate the quantum Sinai billiard problem. It is shown that a noninteracting degenerate electron gas moving in this potential exhibits Drude conductivity in the limit h-bar ..-->.. 0. 15 refs., 4 figs.
Quantum Control and Representation Theory
A. Ibort; J. M. Pérez-Pardo
2012-03-11
A new notion of controllability for quantum systems that takes advantage of the linear superposition of quantum states is introduced. We call such notion von Neumann controllabilty and it is shown that it is strictly weaker than the usual notion of pure state and operator controlability. We provide a simple and effective characterization of it by using tools from the theory of unitary representations of Lie groups. In this sense we are able to approach the problem of control of quantum states from a new perspective, that of the theory of unitary representations of Lie groups. A few examples of physical interest and the particular instances of compact and nilpotent dynamical Lie groups are discussed.
Quantum effects near future singularities
John D. Barrow; Antonio B. Batista; Giuseppe Dito; Julio C. Fabris; M. J. S. Houndjo
2012-01-09
General relativity allows a variety of future singularities to occur in the evolution of the universe. At these future singularities, the universe will end in a singular state after a finite proper time and geometrical invariants of the space time will diverge. One question that naturally arises with respect to these cosmological scenarios is the following: can quantum effects lead to the avoidance of these future singularities? We analyze this problem considering massless and conformally coupled scalar fields in an isotropic and homogeneous background leading to future singularities. It is shown that near strong, big rip-type singularities, with violation of the energy conditions, the quantum effects are very important, while near some milder classes of singularity like the sudden singularity, which preserve the energy conditions, quantum effects are irrelevant.
Effect of noise on time-dependent quantum chaos
Ott, E.; Antonsen T.M. Jr.; Hanson, J.D.
1984-12-03
The dynamics of a time-dependent quantum system can be qualitatively different from that of its classical counterpart when the latter is chaotic. It is shown that small noise can strongly alter this situation.
Quantum Artificial Intelligence
B. Aoun; M. Tarifi
2011-06-04
This report introduces researchers in AI to some of the concepts in quantum heurisitics and quantum AI.
White, Andrew G.
© 2010 Macmillan Publishers Limited. All rights reserved. Towards quantum chemistry on a quantum computer B. P. Lanyon1,2 *, J. D. Whitfield4, G. G. Gillett1,2, M. E. Goggin1,5, M. P. Almeida1,2, I their computational cost grows exponentially with both the number of atoms and basis set size. A solution is to move
A conjecture concerning determinism and phases in quantum mechanics
Arthur Jabs
2015-02-04
It is shown that it is possible to introduce determinism into quantum mechanics by tracing the probabilities in the Born rules back to pseudorandomness in the absolute phase constants of the wave functions. Each wave function is conceived to contain an individual phase factor exp(i alpha). In an ensemble of systems the phase constants alpha are taken to be pseudorandom numbers. A reduction process (collapse) of the wave function, independent of any measurement, is conceived to be a spatial contraction, and a criterion is conjectured of when and where it occurs. It depends on the phase constants of both the considered wave function and that of a small cluster in its environment. A measurement apparatus offers an appropriate environment and associates the point of contraction with an eigenvalue of the observable. The theory is nonlocal and contextual.
Quantum master equation with balanced gain and loss
Dennis Dast; Daniel Haag; Holger Cartarius; Günter Wunner
2014-11-20
We present a quantum master equation describing a Bose-Einstein condensate with particle loss on one lattice site and particle gain on the other lattice site whose mean-field limit is a non-Hermitian PT-symmetric Gross-Pitaevskii equation. It is shown that the characteristic properties of PT-symmetric systems, such as the existence of stationary states and the phase shift of pulses between two lattice sites, are also found in the many-particle system. Visualizing the dynamics on a Bloch sphere allows us to compare the complete dynamics of the master equation with that of the Gross-Pitaevskii equation. We find that even for a relatively small number of particles the dynamics are in excellent agreement and the master equation with balanced gain and loss is indeed an appropriate many-particle description of a PT-symmetric Bose-Einstein condensate.
Xavier Calmet; Priscila de Aquino
2009-10-08
It has recently been shown that if there is a large hidden sector in Nature, the scale of quantum gravity could be much lower than traditionally expected. We study the production of massless gravitons at the LHC and compare our results to those obtained in extra dimensional models. The signature in both cases is missing energy plus jets. In case of non observation, the LHC could be used to put the tightest limit to date on the value of the Planck mass.
Joint probabilities and quantum cognition
Acacio de Barros, J. [Liberal Studies, 1600 Holloway Ave., San Francisco State University, San Francisco, CA 94132 (United States)
2012-12-18
In this paper we discuss the existence of joint probability distributions for quantumlike response computations in the brain. We do so by focusing on a contextual neural-oscillator model shown to reproduce the main features of behavioral stimulus-response theory. We then exhibit a simple example of contextual random variables not having a joint probability distribution, and describe how such variables can be obtained from neural oscillators, but not from a quantum observable algebra.
Schrödinger group and quantum finance
Juan M. Romero; Ulises Lavana; Elio Martínez
2013-04-18
Using the one dimensional free particle symmetries, the quantum finance symmetries are obtained. Namely, it is shown that Black-Scholes equation is invariant under Schr\\"odinger group. In order to do this, the one dimensional free non-relativistic particle and its symmetries are revisited. To get the Black-Scholes equation symmetries, the particle mass is identified as the inverse of square of the volatility. Furthermore, using financial variables, a Schr\\"odinger algebra representation is constructed.
Nuclear quantum effects in water
Joseph A. Morrone; Roberto Car
2008-03-25
In this work, a path integral Car-Parrinello molecular dynamics simulation of liquid water is performed. It is found that the inclusion of nuclear quantum effects systematically improves the agreement of first principles simulations of liquid water with experiment. In addition, the proton momentum distribution is computed utilizing a recently developed open path integral molecular dynamics methodology. It is shown that these results are in good agreement with neutron Compton scattering data for liquid water and ice.
Is there a "most perfect fluid" consistent with quantum field theory?
Thomas D. Cohen
2007-03-05
It was recently conjectured that the ratio of the shear viscosity to entropy density, $ \\eta/ s$, for any fluid always exceeds $\\hbar/(4 \\pi k_B)$. This conjecture was motivated by quantum field theoretic results obtained via the AdS/CFT correspondence and from empirical data with real fluids. A theoretical counterexample to this bound can be constructed from a nonrelativistic gas by increasing the number of species in the fluid while keeping the dynamics essentially independent of the species type. The question of whether the underlying structure of relativistic quantum field theory generically inhibits the realization of such a system and thereby preserves the possibility of a universal bound is considered here. Using rather conservative assumptions, it is shown here that a metastable gas of heavy mesons in a particular controlled regime of QCD provides a realization of the counterexample and is consistent with a well-defined underlying relativistic quantum field theory. Thus, quantum field theory appears to impose no lower bound on $\\eta/s$, at least for metastable fluids.
Tunneling through high energy barriers in simulated quantum annealing
Elizabeth Crosson; Mingkai Deng
2014-10-30
We analyze the performance of simulated quantum annealing (SQA) on an optimization problem for which simulated classical annealing (SA) is provably inefficient because of a high energy barrier. We present evidence that SQA can pass through this barrier to find the global minimum efficiently. This demonstrates the potential for SQA to inherit some of the advantages of quantum annealing (QA), since this problem has been previously shown to be efficiently solvable by quantum adiabatic optimization.
Alessandro Sergi
2009-07-11
A critical assessment of the recent developments of molecular biology is presented. The thesis that they do not lead to a conceptual understanding of life and biological systems is defended. Maturana and Varela's concept of autopoiesis is briefly sketched and its logical circularity avoided by postulating the existence of underlying {\\it living processes}, entailing amplification from the microscopic to the macroscopic scale, with increasing complexity in the passage from one scale to the other. Following such a line of thought, the currently accepted model of condensed matter, which is based on electrostatics and short-ranged forces, is criticized. It is suggested that the correct interpretation of quantum dispersion forces (van der Waals, hydrogen bonding, and so on) as quantum coherence effects hints at the necessity of including long-ranged forces (or mechanisms for them) in condensed matter theories of biological processes. Some quantum effects in biology are reviewed and quantum mechanics is acknowledged as conceptually important to biology since without it most (if not all) of the biological structures and signalling processes would not even exist. Moreover, it is suggested that long-range quantum coherent dynamics, including electron polarization, may be invoked to explain signal amplification process in biological systems in general.
Separation of variables for the classical and quantum Neumann model
O. Babelon; M. Talon
1992-01-16
The method of separation of variables is shown to apply to both the classical and quantum Neumann model. In the classical case this nicely yields the linearization of the flow on the Jacobian of the spectral curve. In the quantum case the Schr\\"odinger equation separates into one--dimensional equations belonging to the class of generalized Lam\\'e differential equations.
Stapp, Henry P
2011-01-01
Robert Griffiths has recently addressed, within the framework of a 'consistent quantum theory' that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues that the putative proofs of this property that involve hidden variables include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. One cannot logically prove properties of a system by establishing, instead, properties of a system modified by adding properties alien to the original system. Hence Griffiths' rejection of hidden-variable-based proofs is logically warranted. Griffiths mentions the existence of a certain alternative proof that does not involve hidden variables, and that uses only macroscopically described observable properties. He notes that he had examined in his book proofs of this general kind, and concluded that they provide no evidence...
Low Energy Quantum System Simulation
Peter Cho; Karl Berggren
2003-10-26
A numerical method for solving Schrodinger's equation based upon a Baker-Campbell-Hausdorff (BCH) expansion of the time evolution operator is presented herein. The technique manifestly preserves wavefunction norm, and it can be applied to problems in any number of spatial dimensions. We also identify a particular dimensionless ratio of potential to kinetic energies as a key coupling constant. This coupling establishes characteristic length and time scales for a large class of low energy quantum states, and it guides the choice of step sizes in numerical work. Using the BCH method in conjunction with an imaginary time rotation, we compute low energy eigenstates for several quantum systems coupled to non-trivial background potentials. The approach is subsequently applied to the study of 1D propagating wave packets and 2D bound state time development. Failures of classical expectations uncovered by simulations of these simple systems help develop quantum intuition. Finally, we investigate the response of a Superconducting Quantum Interference Device (SQUID) to a time dependent potential. We discuss how to engineer the potential's energy and time scales so that the SQUID acts as a quantum NOT gate. The notional simulation we present for this gate provides useful insight into the design of one candidate building block for a quantum computer.
Alliance to lower electricity costs and increase reliance on clean energy sources. The group government agencies to increase their reliance on clean energy sources. As part of this effort, Chicago has Technology shown here. CityofChicago Aggregated Purchasing--A Clean Energy Strategy SOLAR TODAY Aggregated
K. Wiesner
2008-08-05
Quantum cellular automata (QCA) are reviewed, including early and more recent proposals. QCA are a generalization of (classical) cellular automata (CA) and in particular of reversible CA. The latter are reviewed shortly. An overview is given over early attempts by various authors to define one-dimensional QCA. These turned out to have serious shortcomings which are discussed as well. Various proposals subsequently put forward by a number of authors for a general definition of one- and higher-dimensional QCA are reviewed and their properties such as universality and reversibility are discussed.
Photonic quantum walk in a single beam with twisted light
Cardano, Filippo; Karimi, Ebrahim; Slussarenko, Sergei; Paparo, Domenico; de Lisio, Corrado; Sciarrino, Fabio; Santamato, Enrico; Marrucci, Lorenzo
2014-01-01
Inspired by the classical phenomenon of random walk, the concept of quantum walk has emerged recently as a powerful platform for the dynamical simulation of complex quantum systems, entanglement production and universal quantum computation. Such a wide perspective motivates a renewing search for efficient, scalable and stable implementations of this quantum process. Photonic approaches have hitherto mainly focused on multi-path schemes, requiring interferometric stability and a number of optical elements that scales quadratically with the number of steps. Here we report the experimental realization of a quantum walk taking place in the orbital angular momentum space of light, both for a single photon and for two simultaneous indistinguishable photons. The whole process develops in a single light beam, with no need of interferometers, and requires optical resources scaling linearly with the number of steps. Our demonstration introduces a novel versatile photonic platform for implementing quantum simulations, b...
Quantum computer of wire circuit architecture
S. A. Moiseev; F. F. Gubaidullin; S. N. Andrianov
2010-01-07
First solid state quantum computer was built using transmons (cooper pair boxes). The operation of the computer is limited because of using a number of the rigit cooper boxes working with fixed frequency at temperatures of superconducting material. Here, we propose a novel architecture of quantum computer based on a flexible wire circuit of many coupled quantum nodes containing controlled atomic (molecular) ensembles. We demonstrate wide opportunities of the proposed computer. Firstly, we reveal a perfect storage of external photon qubits to multi-mode quantum memory node and demonstrate a reversible exchange of the qubits between any arbitrary nodes. We found optimal parameters of atoms in the circuit and self quantum modes for quantum processing. The predicted perfect storage has been observed experimentally for microwave radiation on the lithium phthalocyaninate molecule ensemble. Then also, for the first time we show a realization of the efficient basic two-qubit gate with direct coupling of two arbitrary nodes by using appropriate atomic frequency shifts in the circuit nodes. Proposed two-qubit gate runs with a speed drastically accelerated proportionally to the number of atoms in the node. The direct coupling and accelerated two-qubit gate can be realized for large number of the circuit nodes. Finally, we describe two and three-dimensional scalable architectures that pave the road to construction of universal multi-qubit quantum computer operating at room temperatures.
New Hampshire, University of
Rabies Requirements for NH 4-H Animals Upon the recommendation of the New Hampshire State Veterinarian, all mammals shown or exhibited at New Hampshire 4-H events including fairs, shows, clinics, 4-H and fairs may have additional vaccination and health requirements as recommended by the New Hampshire State
LaValle, Steven M.
1 Nash Equilibrium for mixed strategies Nash shown that every nonÂcooperative game with finite sets of pure strategies has at least one mixed strategy equilibrium pair. We define such pair as a Nash respectively, the strategy (y # , z # ) is a Nash equilibrium if: y # T Az # # y T Az # #y # Y y # T Bz # # y
Norris, Ray
to the enormous sensitivity of the Square Kilometre Array, which is still a decade away, but due to its of galaxies. Keywords: astronomy; data; radio-astronomy I. INTRODUCTION The Square Kilometre Array (SKA in 2012. Shown are a few of the 36 12-metre dishes, each equipped with a 100-pixel Phased Array Feed
Touch, Joe
as a "parking lot", where packets from different "roads" are parked and separately retrieved. Current electronicAbstract A 32x32 optical packet switch design using only four packets of variable delay is shown 95 packet multiplexing. Our design shows that only four packets of optical switched-delay line can multiplex
de Weck, Olivier L.
Air-Breathing Propulsion Qualifier Question - 2012 A gas turbine jet engine, shown schematically compressor, a combustion chamber (combustor), a single stage turbine, and an ideally expanded nozzle (nozzle ratio ( C = Tt2 /Tt1 ), what is the turbine stagnation temperature ratio T = Tt4 /Tt3 ? (Suggestion
Maini, Philip K.
Spots and stripes: Pleomorphic patterning of stem cells via p-ERK-dependent cell chemotaxis shown cells Placode ERK Mathematical modeling Chemotaxis A key issue in stem cell biology patterns, ranging from stripes to spots, can be obtained when the level of p-ERK activity is adjusted
Shoubridge, Eric
#12;THE `TEST STATISTICS REPORT' provides a synopsis of the test attributes and some important statistics. A sample is shown here to the right. The Test reliability indicators are measures of how well: Are formulae for testing reliability as a measure of internal consistency. Higher values indicate a stronger
Landers, Robert G.
ElectroMechanical Systems QUESTION 1 A transducer used to measure translational motion is shown variables and inputs. #12;ElectroMechanical Systems 2 L R ei(t) + - M K B N S I(t) Figure 2.1 QUESTION 3 of state equations describing the system dynamics. d. Determine the state variables and inputs. #12;ElectroMechanical
Gates, Kent. S.
Name______________________________________Drug-like Properties all answers must fit in space provided 1 Imagine that a drug discovery program generated the two lead compounds shown below designed to facilitate drug discovery. We'll be using a free, web-based application that calculates drug
Fish, Frank
Several groups of fishes have been shown to use or are suspected of using water jets from, 1987; Pietsch and Grobecker, 1987). Most studies of jet propulsion in fishes have been concerned with multiple jets that produce continuous, if somewhat staccato, locomotion. Some sources, however, have
Thole, Karen A.
along a gas turbine airfoil, particularly for the first stage nozzle guide vane. For this study of the variables affecting boundary layer development on gas turbine airfoils, studies need to be performed of a variety of gas turbine combustors have shown that the levels can range between 8% and 40% (Kuotmos and Mc
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
with a length of 35 cm, which certainly helps . With Avogadro's number and the density of liquid hydrogen, we have about 1024 protons per cm2. We then take the beam of 160...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
September 2002 Page 1 KPA Activity Number KPA Activity SEM Section SME Work Product SQSE Web Site http:cio.doe.govsqse REQUIREMENTS MANAGEMENT RM-1 The software engineering...
Surface code quantum communication
Austin G. Fowler; David S. Wang; Charles D. Hill; Thaddeus D. Ladd; Rodney Van Meter; Lloyd C. L. Hollenberg
2010-02-05
Quantum communication typically involves a linear chain of repeater stations, each capable of reliable local quantum computation and connected to their nearest neighbors by unreliable communication links. The communication rate in existing protocols is low as two-way classical communication is used. We show that, if Bell pairs are generated between neighboring stations with a probability of heralded success greater than 0.65 and fidelity greater than 0.96, two-way classical communication can be entirely avoided and quantum information can be sent over arbitrary distances with arbitrarily low error at a rate limited only by the local gate speed. The number of qubits per repeater scales logarithmically with the communication distance. If the probability of heralded success is less than 0.65 and Bell pairs between neighboring stations with fidelity no less than 0.92 are generated only every T_B seconds, the logarithmic resource scaling remains and the communication rate through N links is proportional to 1/(T_B log^2 N).
Quantum arithmetic with the Quantum Fourier Transform
Lidia Ruiz-Perez; Juan Carlos Garcia-Escartin
2014-11-21
The Quantum Fourier Transform offers an interesting way to perform arithmetic operations on a quantum computer. We review existing Quantum Fourier Transform adders and multipliers and propose some modifications that extend their capabilities. Among the new circuits, we propose a quantum method to compute the weighted average of a series of inputs in the transform domain.
Quantum chaos viewed from quantum action
D. Huard; H. Kröger; G. Melkonyan; L. P. Nadeau; K. J. M. Moriarty
2004-06-18
We consider a mixed chaotic Hamiltonian system and compare classical with quantum chaos. As alternative to the methods of enegy level spacing statistics and trace formulas, we construct a quantum action and a quantum analogue phase space to analyse quantum chaos.
Quantum Chaos via the Quantum Action
H. Kröger
2002-12-16
We discuss the concept of the quantum action with the purpose to characterize and quantitatively compute quantum chaos. As an example we consider in quantum mechanics a 2-D Hamiltonian system - harmonic oscillators with anharmonic coupling - which is classically a chaotic system. We compare Poincar\\'e sections obtained from the quantum action with those from the classical action.
Quantum++ - A C++11 quantum computing library
Vlad Gheorghiu
2014-12-15
Quantum++ is a general-purpose multi-threaded quantum computing library written in C++11 and composed solely of header files. The library is not restricted to qubit systems or specific quantum information processing tasks, being capable of simulating arbitrary quantum processes. The main design factors taken in consideration were ease of use, portability, and performance.
Mode Competition in Dual-Mode Quantum Dots Semiconductor Microlaser
Chusseau, Laurent; Viktorovitch, P; Letartre, Xavier
2013-01-01
This paper describes the modeling of quantum dots lasers with the aim of assessing the conditions for stable cw dual-mode operation when the mode separation lies in the THz range. Several possible models suited for InAs quantum dots in InP barriers are analytically evaluated, in particular quantum dots electrically coupled through a direct exchange of excitation by the wetting layer or quantum dots optically coupled through the homogeneous broadening of their optical gain. A stable dual-mode regime is shown possible in all cases when quantum dots are used as active layer whereas a gain medium of quantum well or bulk type inevitably leads to bistable behavior. The choice of a quantum dots gain medium perfectly matched the production of dual-mode lasers devoted to THz generation by photomixing.
Mode Competition in Dual-Mode Quantum Dots Semiconductor Microlaser
Laurent Chusseau; Fabrice Philippe; P. Viktorovitch; Xavier Letartre
2013-03-07
This paper describes the modeling of quantum dots lasers with the aim of assessing the conditions for stable cw dual-mode operation when the mode separation lies in the THz range. Several possible models suited for InAs quantum dots in InP barriers are analytically evaluated, in particular quantum dots electrically coupled through a direct exchange of excitation by the wetting layer or quantum dots optically coupled through the homogeneous broadening of their optical gain. A stable dual-mode regime is shown possible in all cases when quantum dots are used as active layer whereas a gain medium of quantum well or bulk type inevitably leads to bistable behavior. The choice of a quantum dots gain medium perfectly matched the production of dual-mode lasers devoted to THz generation by photomixing.
Surface electromagnetic wave equations in a warm magnetized quantum plasma
Li, Chunhua; Yang, Weihong [Department of Modern Physics, University of Science and Technology of China, 230026 Hefei (China); Wu, Zhengwei, E-mail: wuzw@ustc.edu.cn [Department of Modern Physics, University of Science and Technology of China, 230026 Hefei (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Center of Low Temperature Plasma Application, Yunnan Aerospace Industry Company, Kunming, 650229 Yunnan (China); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)
2014-07-15
Based on the single-fluid plasma model, a theoretical investigation of surface electromagnetic waves in a warm quantum magnetized inhomogeneous plasma is presented. The surface electromagnetic waves are assumed to propagate on the plane between a vacuum and a warm quantum magnetized plasma. The quantum magnetohydrodynamic model includes quantum diffraction effect (Bohm potential), and quantum statistical pressure is used to derive the new dispersion relation of surface electromagnetic waves. And the general dispersion relation is analyzed in some special cases of interest. It is shown that surface plasma oscillations can be propagated due to quantum effects, and the propagation velocity is enhanced. Furthermore, the external magnetic field has a significant effect on surface wave's dispersion equation. Our work should be of a useful tool for investigating the physical characteristic of surface waves and physical properties of the bounded quantum plasmas.
Heavy pair production currents with general quantum numbers in...
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(c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA) Country of Publication: United States Language: English Subject: 72...
Heavy pair production currents with general quantum numbers in
Office of Scientific and Technical Information (OSTI)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefieldSulfate Reducing(Journal Article)lasers (Journal Article) |different| SciTech
The Chern-Simons Number as a Dynamical Variable
Tye, S -H Henry
2016-01-01
In the standard electroweak theory that describes nature, the Chern-Simons number associated with the vacua as well as the unstable sphaleron solutions play a crucial role in the baryon number violating processes. We recall why the Chern-Simons number should be generalized from a set of discrete values to a dynamical (quantum) variable. Via the construction of an appropriate Hopf invariant and the winding number, we discuss how the geometric information in the gauge fields is also captured in the Higgs field. We then discuss the choice of the Hopf variable in relation to the Chern-Simons variable.
John Ashmead
2010-05-05
Normally we quantize along the space dimensions but treat time classically. But from relativity we expect a high level of symmetry between time and space. What happens if we quantize time using the same rules we use to quantize space? To do this, we generalize the paths in the Feynman path integral to include paths that vary in time as well as in space. We use Morlet wavelet decomposition to ensure convergence and normalization of the path integrals. We derive the Schr\\"odinger equation in four dimensions from the short time limit of the path integral expression. We verify that we recover standard quantum theory in the non-relativistic, semi-classical, and long time limits. Quantum time is an experiment factory: most foundational experiments in quantum mechanics can be modified in a way that makes them tests of quantum time. We look at single and double slits in time, scattering by time-varying electric and magnetic fields, and the Aharonov-Bohm effect in time.
Nikolaj Moll; Andreas Fuhrer; Peter Staar; Ivano Tavernelli
2015-10-14
Quantum chemistry simulations on a quantum computer suffer from the overhead needed for encoding the fermionic problem in a bosonic system of qubits. By exploiting the block diagonality of a fermionic Hamiltonian, we show that the number of required qubits can be reduced by a factor of two or more. There is no need to go into the basis of the Hilbert space for this reduction because all operations can be performed in the operator space. The scheme is conceived as a pre-computational step that would be performed on a classical computer prior to the actual quantum simulation. We apply this scheme to reduce the number of qubits necessary to simulate both the Hamiltonian of the two-site Fermi-Hubbard model and the hydrogen molecule. Both quantum systems can then be simulated with a two-qubit quantum computer.
Quantum Error Correction for Quantum Memories
Barbara M. Terhal
2015-04-10
Active quantum error correction using qubit stabilizer codes has emerged as a promising, but experimentally challenging, engineering program for building a universal quantum computer. In this review we consider the formalism of qubit stabilizer and subsystem stabilizer codes and their possible use in protecting quantum information in a quantum memory. We review the theory of fault-tolerance and quantum error-correction, discuss examples of various codes and code constructions, the general quantum error correction conditions, the noise threshold, the special role played by Clifford gates and the route towards fault-tolerant universal quantum computation. The second part of the review is focused on providing an overview of quantum error correction using two-dimensional (topological) codes, in particular the surface code architecture. We discuss the complexity of decoding and the notion of passive or self-correcting quantum memories. The review does not focus on a particular technology but discusses topics that will be relevant for various quantum technologies.
Quantum Computation of Scattering in Scalar Quantum Field Theories
Stephen P. Jordan; Keith S. M. Lee; John Preskill
2011-12-20
Quantum field theory provides the framework for the most fundamental physical theories to be confirmed experimentally, and has enabled predictions of unprecedented precision. However, calculations of physical observables often require great computational complexity and can generally be performed only when the interaction strength is weak. A full understanding of the foundations and rich consequences of quantum field theory remains an outstanding challenge. We develop a quantum algorithm to compute relativistic scattering amplitudes in massive phi-fourth theory in spacetime of four and fewer dimensions. The algorithm runs in a time that is polynomial in the number of particles, their energy, and the desired precision, and applies at both weak and strong coupling. Thus, it offers exponential speedup over existing classical methods at high precision or strong coupling.
Quantum computing in a piece of glass
Warner A. Miller; Grigoriy Kreymerman; Christopher Tison; Paul M. Alsing; Jonathan R. McDonald
2011-12-15
Quantum gates and simple quantum algorithms can be designed utilizing the diffraction phenomena of a photon within a multiplexed holographic element. The quantum eigenstates we use are the photon's linear momentum (LM) as measured by the number of waves of tilt across the aperture. Two properties of quantum computing within the circuit model make this approach attractive. First, any conditional measurement can be commuted in time with any unitary quantum gate - the timeless nature of quantum computing. Second, photon entanglement can be encoded as a superposition state of a single photon in a higher-dimensional state space afforded by LM. Our theoretical and numerical results indicate that OptiGrate's photo-thermal refractive (PTR) glass is an enabling technology. We will review our previous design of a quantum projection operator and give credence to this approach on a representative quantum gate grounded on coupled-mode theory and numerical simulations, all with parameters consistent with PTR glass. We discuss the strengths (high efficiencies, robustness to environment) and limitations (scalability, crosstalk) of this technology. While not scalable, the utility and robustness of such optical elements for broader quantum information processing applications can be substantial.
When is a quantum heat engine quantum?
Alexander Friedenberger; Eric Lutz
2015-08-17
Quantum thermodynamics studies quantum effects in thermal machines. But when is a heat engine, which cyclically interacts with external reservoirs that unavoidably destroy its quantum coherence, really quantum? We here use the Leggett-Garg inequality to assess the nonclassical properties of a single two-level Otto engine. We provide the complete phase diagram characterizing the quantumness of the engine as a function of its parameters and identify three distinct phases. We further derive an explicit expression for the transition temperature.
Quantum Heat Engines Using Superconducting Quantum Circuits
H. T. Quan; Y. D. Wang; Yu-xi Liu; C. P. Sun; Franco Nori
2006-09-14
We propose a quantum analog of the internal combustion engine used in most cars. Specifically, we study how to implement the Otto-type quantum heat engine (QHE) with the assistance of a Maxwell's demon. Three steps are required: thermalization, quantum measurement, and quantum feedback controlled by the Maxwell demon. We derive the positive-work condition of this composite QHE. Our QHE can be constructed using superconducting quantum circuits. We explicitly demonstrate the essential role of the demon in this macroscopic QHE.
Dual trapped-ion quantum simulators: an alternative route towards exotic quantum magnets
Graß, Tobias; Bermudez, Alejandro
2015-01-01
We present a route towards the quantum simulation of exotic quantum magnetism in ion traps by exploiting dual relations between different spin models. Our strategy allows one to start from Hamiltonians that can be realized with current technology, while properties of an exotic dual model are inferred from measurements of non-local, string-order-like, operators. The latter can be achieved from fluorescence, or from certain spectroscopic measurements, both of which can be combined with finite-size scaling by controlling the number of ions in the dual quantum simulator. We apply this concept to propose quantum simulators of frustrated quantum magnets, and Ising models with multi-spin interactions. We test the validity of the idea by showing numerically that the predictions of an ideal dual quantum simulator are not qualitatively modified by relevant perturbations that occur naturally in the trapped-ion scenario.
Nelson, R.N.
1985-05-01
This publication lists all report number codes processed by the Office of Scientific and Technical Information. The report codes are substantially based on the American National Standards Institute, Standard Technical Report Number (STRN)-Format and Creation Z39.23-1983. The Standard Technical Report Number (STRN) provides one of the primary methods of identifying a specific technical report. The STRN consists of two parts: The report code and the sequential number. The report code identifies the issuing organization, a specific program, or a type of document. The sequential number, which is assigned in sequence by each report issuing entity, is not included in this publication. Part I of this compilation is alphabetized by report codes followed by issuing installations. Part II lists the issuing organization followed by the assigned report code(s). In both Parts I and II, the names of issuing organizations appear for the most part in the form used at the time the reports were issued. However, for some of the more prolific installations which have had name changes, all entries have been merged under the current name.
Treating Time Travel Quantum Mechanically
John-Mark A. Allen
2014-10-10
The fact that closed timelike curves (CTCs) are permitted by general relativity raises the question as to how quantum systems behave when time travel to the past occurs. Research into answering this question by utilising the quantum circuit formalism has given rise to two theories: Deutschian-CTCs (D-CTCs) and "postselected" CTCs (P-CTCs). In this paper the quantum circuit approach is thoroughly reviewed, and the strengths and shortcomings of D-CTCs and P-CTCs are presented in view of their non-linearity and time travel paradoxes. In particular, the "equivalent circuit model"---which aims to make equivalent predictions to D-CTCs, while avoiding some of the difficulties of the original theory---is shown to contain errors. The discussion of D-CTCs and P-CTCs is used to motivate an analysis of the features one might require of a theory of quantum time travel, following which two overlapping classes of new theories are identified. One such theory, the theory of "transition probability" CTCs (T-CTCs), is fully developed. The theory of T-CTCs is shown not to have certain undesirable features---such as time travel paradoxes, the ability to distinguish non-orthogonal states with certainty, and the ability to clone or delete arbitrary pure states---that are present with D-CTCs and P-CTCs. The problems with non-linear extensions to quantum mechanics are discussed in relation to the interpretation of these theories, and the physical motivations of all three theories are discussed and compared.
LaValle, Steven M.
1 Nash Equilibrium for mixed strategies Nash shown that every non-cooperative game with finite sets of pure strategies has at least one mixed strategy equilibrium pair. We define such pair as a Nash respectively, the strategy (y, z) is a Nash equilibrium if: yT Az y T Az y Y yT Bz yT Bz z Z in which Y
Harsij, Zeynab Mirza, Behrouz
2014-12-15
A helicity entangled tripartite state is considered in which the degree of entanglement is preserved in non-inertial frames. It is shown that Quantum Entanglement remains observer independent. As another measure of quantum correlation, Quantum Discord has been investigated. It is explicitly shown that acceleration has no effect on the degree of quantum correlation for the bipartite and tripartite helicity entangled states. Geometric Quantum Discord as a Hilbert–Schmidt distance is computed for helicity entangled states. It is shown that living in non-inertial frames does not make any influence on this distance, either. In addition, the analysis has been extended beyond single mode approximation to show that acceleration does not have any impact on the quantum features in the limit beyond the single mode. As an interesting result, while the density matrix depends on the right and left Unruh modes, the Negativity as a measure of Quantum Entanglement remains constant. Also, Quantum Discord does not change beyond single mode approximation. - Highlights: • The helicity entangled states here are observer independent in non-inertial frames. • It is explicitly shown that Quantum Discord for these states is observer independent. • Geometric Quantum Discord is also not affected by acceleration increase. • Extending to beyond single mode does not change the degree of entanglement. • Beyond single mode approximation the degree of Quantum Discord is also preserved.
Quantum coherent states in cosmology
Houri Ziaeepour
2015-02-15
Coherent states consist of superposition of infinite number of particles and do not have a classical analogue. We study their evolution in a FLRW cosmology and show that only when full quantum corrections are considered, they may survive the expansion of the Universe and form a global condensate. This state of matter can be the origin of accelerating expansion of the Universe, generally called dark energy, and inflation in the early universe. Additionally, such a quantum pool may be the ultimate environment for decoherence at shorter distances. If dark energy is a quantum coherent state, its dominant contribution to the total energy of the Universe at present provides a low entropy state which may be necessary as an initial condition for a new Big Bang in the framework of bouncing cosmology models.
Massive Parallel Quantum Computer Simulator
K. De Raedt; K. Michielsen; H. De Raedt; B. Trieu; G. Arnold; M. Richter; Th. Lippert; H. Watanabe; N. Ito
2006-08-30
We describe portable software to simulate universal quantum computers on massive parallel computers. We illustrate the use of the simulation software by running various quantum algorithms on different computer architectures, such as a IBM BlueGene/L, a IBM Regatta p690+, a Hitachi SR11000/J1, a Cray X1E, a SGI Altix 3700 and clusters of PCs running Windows XP. We study the performance of the software by simulating quantum computers containing up to 36 qubits, using up to 4096 processors and up to 1 TB of memory. Our results demonstrate that the simulator exhibits nearly ideal scaling as a function of the number of processors and suggest that the simulation software described in this paper may also serve as benchmark for testing high-end parallel computers.
Integrability and nonintegrability of quantum systems. II. Dynamics in quantum phase space
Zhang, Weimin (Department of Physics, FM-15, University of Washington, Seattle, WA (USA) Department of Physics and Atmospheric Science, Drexel University, Philadelphia, PA (USA)); Feng, D.H.; Yuan, Jianmin (Department of Physics and Atmospheric Science, Drexel University, Philadelphia, PA (USA))
1990-12-15
Based on the concepts of integrability and nonintegrability of a quantum system presented in a previous paper (Zhang, Feng, Yuan, and Wang, Phys. Rev. A 40, 438 (1989)), a realization of the dynamics in the quantum phase space is now presented. For a quantum system with dynamical group {ital G-script} and in one of its unitary irreducible-representation carrier spaces {ital h-german}{sub {Lambda}}, the quantum phase space is a 2{ital M}{sub {Lambda}}-dimensional topological space, where {ital M}{sub {Lambda}} is the quantum-dynamical degrees of freedom. This quantum phase space is isomorphic to a coset space {ital G-script}/{ital H-script} via the unitary exponential mapping of the elementary excitation operator subspace of {ital g-script} (algebra of {ital G-script}), where {ital H-script} ({contained in}{ital G-script}) is the maximal stability subgroup of a fixed state in {ital h-german}{sub {Lambda}}. The phase-space representation of the system is realized on {ital G-script}/{ital H-script}, and its classical analogy can be obtained naturally. It is also shown that there is consistency between quantum and classical integrability. Finally, a general algorithm for seeking the manifestation of quantum chaos'' via the classical analogy is provided. Illustrations of this formulation in several important quantum systems are presented.
Energy Content of Quantum Systems and the Alleged Collapse of the Wavefunction
Peter J. Riggs
2009-10-15
It is shown that within a quantum system, the wave field has a (potential) energy content that can be exchanged with quantum particles. Energy conservation in quantum systems holds if potential energy is correctly taken to be a field attribute. From this perspective, a transfer of energy occurs on measurement from the wave field to a quantum particle and this provides a physical explanation of what is commonly referred to as the collapse of the wavefunction.
Quantum Nonsymmetric Gravity and The Superfiber Bundle Formalism
Mebarki, N
1999-01-01
The formalism of the principal superfiber-bundle is applied to quantum Nonsymmetric gravitationl theory. It is shown that the metric and Faddev-Popov fields arise as superfields components of the superconnection. Moreover,the BRST and anti-BRST transformations are shown to be the gauge transformations of parameters the ghost and anti-ghost superfields.
Quantum Strongly Secure Ramp Secret Sharing
Paul Zhang; Ryutaroh Matsumoto
2014-08-08
Quantum secret sharing is a scheme for encoding a quantum state (the secret) into multiple shares and distributing them among several participants. If a sufficient number of shares are put together, then the secret can be fully reconstructed. If an insufficient number of shares are put together however, no information about the secret can be revealed. In quantum ramp secret sharing, partial information about the secret is allowed to leak to a set of participants, called an unqualified set, that cannot fully reconstruct the secret. By allowing this, the size of a share can be drastically reduced. This paper introduces a quantum analog of classical strong security in ramp secret sharing schemes. While the ramp secret sharing scheme still leaks partial information about the secret to unqualified sets of participants, the strong security condition ensures that qudits with critical information can no longer be leaked.
A bridge to lower overhead quantum computation
Austin G. Fowler; Simon J. Devitt
2013-04-09
Two primary challenges stand in the way of practical large-scale quantum computation, namely achieving sufficiently low error rate quantum gates and implementing interesting quantum algorithms with a physically reasonable number of qubits. In this work we address the second challenge, presenting a new technique, bridge compression, which enables remarkably low volume structures to be found that implement complex computations in the surface code. The surface code has a number of highly desirable properties, including the ability to achieve arbitrarily reliable computation given sufficient qubits and quantum gate error rates below approximately 1%, and the use of only a 2-D array of qubits with nearest neighbor interactions. As such, our compression technique is of great practical relevance.
Strong quantum scarring by local impurities
Perttu J. J. Luukko; Byron Drury; Anna Klales; Lev Kaplan; Eric J. Heller; Esa Räsänen
2015-12-07
We discover and characterize strong quantum scars, or eigenstates resembling classical periodic orbits, in two-dimensional quantum wells perturbed by local impurities. These scars are not explained by ordinary scar theory, which would require the existence of short, moderately unstable periodic orbits in the perturbed system. Instead, they are supported by classical resonances in the unperturbed system and the resulting quantum near-degeneracy. Even in the case of a large number of randomly scattered impurities, the scars prefer distinct orientations that extremize the overlap with the impurities. We demonstrate that these preferred orientations can be used for highly efficient transport of quantum wave packets across the perturbed potential landscape. Assisted by the scars, wave-packet recurrences are significantly stronger than in the unperturbed system. Together with the controllability of the preferred orientations, this property may be very useful for quantum transport applications.
What is Dynamics in Quantum Gravity?
Malkiewicz, Przemyslaw
2015-01-01
Dynamics of general relativistic systems is given with respect to internal clocks. We investigate the extent to which the choice of internal clock in quantum description of the gravitational field determines the quantum dynamics. We develop our method by making use of the Hamilton-Jacobi theory, which is extended to include time coordinate transformations. Next, we apply our method to a quantum model of the flat Friedmann universe and compute some clock-induced deviations to semiclassical phase space portrait. Within a fixed quantization we find the abundance of possible semiclassical extensions to general relativity by switching between clocks. It follows that quantities like minimal volume, maximal curvature and even a number of quantum bounces, often used to describe quantum effects in gravity, are ill-defined.
What is Dynamics in Quantum Gravity?
Przemyslaw Malkiewicz
2015-05-18
Dynamics of general relativistic systems is given with respect to internal clocks. We investigate the extent to which the choice of internal clock in quantum description of the gravitational field determines the quantum dynamics. We develop our method by making use of the Hamilton-Jacobi theory, which is extended to include time coordinate transformations. Next, we apply our method to a quantum model of the flat Friedmann universe and compute some clock-induced deviations to semiclassical phase space portrait. Within a fixed quantization we find the abundance of possible semiclassical extensions to general relativity by switching between clocks. It follows that quantities like minimal volume, maximal curvature and even a number of quantum bounces, often used to describe quantum effects in gravity, are ill-defined.
Investigating student understanding of quantum entanglement
Kohnle, Antje
2015-01-01
Quantum entanglement is a central concept of quantum theory for multiple particles. Entanglement played an important role in the development of the foundations of the theory and makes possible modern applications in quantum information technology. As part of the QuVis Quantum Mechanics Visualization Project, we developed an interactive simulation "Entanglement: The nature of quantum correlations" using two-particle entangled spin states. We investigated student understanding of entanglement at the introductory and advanced undergraduate levels by collecting student activity and post-test responses using two versions of the simulation and carrying out a small number of student interviews. Common incorrect ideas found include statements that all entangled states must be maximally entangled (i.e. show perfect correlations or anticorrelations along all common measurement axes), that the spins of particles in a product state must have definite values (cannot be in a superposition state with respect to spin) and di...
Quantum Properties of Double Kicked Systems with Classical Translational Invariance in Momentum
Itzhack Dana
2015-01-21
Double kicked rotors (DKRs) appear to be the simplest nonintegrable Hamiltonian systems featuring classical translational symmetry in phase space (i.e., in angular momentum) for an \\emph{infinite} set of values (the rational ones) of a parameter $\\eta$. The experimental realization of quantum DKRs by atom-optics methods motivates the study of the double kicked particle (DKP). The latter reduces, at any fixed value of the conserved quasimomentum $\\beta\\hbar$, to a generalized DKR, the \\textquotedblleft $\\beta $-DKR\\textquotedblright . We determine general quantum properties of $\\beta $-DKRs and DKPs for arbitrary rational $\\eta $. The quasienergy problem of $\\beta $-DKRs is shown to be equivalent to the energy eigenvalue problem of a finite strip of coupled lattice chains. Exact connections are then obtained between quasienergy spectra of $\\beta $-DKRs for all $\\beta $ in a generically infinite set. The general conditions of quantum resonance for $\\beta $-DKRs are shown to be the simultaneous rationality of $\\eta $, $\\beta$, and a scaled Planck constant $\\hbar _{\\mathrm{S}}$. For rational $\\hbar _{\\mathrm{S}}$ and generic values of $\\beta $, the quasienergy spectrum is found to have a staggered-ladder structure. Other spectral structures, resembling Hofstadter butterflies, are also found. Finally, we show the existence of particular DKP wave-packets whose quantum dynamics is \\emph{free}, i.e., the evolution frequencies of expectation values in these wave-packets are independent of the nonintegrability. All the results for rational $\\hbar _{\\mathrm{S}}$ exhibit unique number-theoretical features involving $\\eta $, $\\hbar _{\\mathrm{S}}$, and $\\beta $.
Holography from quantum cosmology
M. Rashki; S. Jalalzadeh
2014-12-12
The Weyl-Wigner-Groenewold-Moyal formalism of deformation quantization is applied to the closed Friedmann-Lema\\^itre-Robertson-Walker (FLRW) cosmological model. We show that the phase space average for the surface of the apparent horizon is quantized in units of the Planck's surface, and that the total entropy of the universe is also quantized. Taking into account these two concepts, it is shown that 't Hooft conjecture on the cosmological holographic principle (CHP) in radiation and dust dominated quantum universes is satisfied as a manifestation of quantization. This suggests that the entire universe (not only inside the apparent horizon) can be seen as a two-dimensional information structure encoded on the apparent horizon.
Antieigenvalue Analysis, New Applications: Continuum Mechanics, Economics, Number Theory
Karl Gustafson
2015-04-20
My recent book Antieigenvalue Analysis, World-Scientific, 2012, presented the theory of antieigenvalues from its inception in 1966 up to 2010, and its applications within those forty-five years to Numerical Analysis, Wavelets, Statistics, Quantum Mechanics, Finance, and Optimization. Here I am able to offer three further areas of application: Continuum Mechanics, Economics, and Number Theory.
Unpredictability and the transmission of numbers
John M. Myers; F. Hadi Madjid
2015-08-05
Curiously overlooked in physics is its dependence on the transmission of numbers. For example the transmission of numerical clock readings is implicit in the concept of a coordinate system. The transmission of numbers and other logical distinctions is often achieved over a computer-mediated communications network in the face of an unpredictable environment. By unpredictable we mean something stronger than the spread of probabilities over given possible outcomes, namely an opening to unforeseeable possibilities. Unpredictability, until now overlooked in theoretical physics, makes the transmission of numbers interesting. Based on recent proofs within quantum theory that provide a theoretical foundation to unpredictability, here we show how regularities in physics rest on a background of channels over which numbers are transmitted. As is known to engineers of digital communications, numerical transmissions depend on coordination reminiscent of the cycle of throwing and catching by players tossing a ball back and forth. In digital communications, the players are computers, and the required coordination involves unpredictably adjusting "live clocks" that step these computers through phases of a cycle. We show how this phasing, which we call `logical synchronization,' constrains number-carrying networks, and, if a spacetime manifold in invoked, put "stripes" on spacetime. Via its logically synchronized channels, a network of live clocks serves as a reference against which to locate events. Such a network in any case underpins a coordinate frame, and in some cases the direct use of a network can be tailored to investigate an unpredictable environment. Examples include explorations of gravitational variations near Earth.
Ancilla-Assisted Discrimination of Quantum Gates
Jianxin Chen; Mingsheng Ying
2008-09-02
The intrinsic idea of superdense coding is to find as many gates as possible such that they can be perfectly discriminated. In this paper, we consider a new scheme of discrimination of quantum gates, called ancilla-assisted discrimination, in which a set of quantum gates on a $d-$dimensional system are perfectly discriminated with assistance from an $r-$dimensional ancilla system. The main contribution of the present paper is two-fold: (1) The number of quantum gates that can be discriminated in this scheme is evaluated. We prove that any $rd+1$ quantum gates cannot be perfectly discriminated with assistance from the ancilla, and there exist $rd$ quantum gates which can be perfectly discriminated with assistance from the ancilla. (2) The dimensionality of the minimal ancilla system is estimated. We prove that there exists a constant positive number $c$ such that for any $k\\leq cr$ quantum gates, if they are $d$-assisted discriminable, then they are also $r$-assisted discriminable, and there are $c^{\\prime}r\\textrm{}(c^{\\prime}>c)$ different quantum gates which can be discriminated with a $d-$dimensional ancilla, but they cannot be discriminated if the ancilla is reduced to an $r-$dimensional system. Thus, the order $O(r)$ of the number of quantum gates that can be discriminated with assistance from an $r-$dimensional ancilla is optimal. The results reported in this paper represent a preliminary step toward understanding the role ancilla system plays in discrimination of quantum gates as well as the power and limit of superdense coding.
Control Landscapes for Observable Preparation with Open Quantum Systems
Rebing Wu; Alexander Pechen; Herschel Rabitz; Michael Hsieh; Benjamin Tsou
2007-08-16
A quantum control landscape is defined as the observable as a function(al) of the system control variables. Such landscapes were introduced to provide a basis to understand the increasing number of successful experiments controlling quantum dynamics phenomena. This paper extends the concept to encompass the broader context of the environment having an influence. For the case that the open system dynamics are fully controllable, it is shown that the control landscape for open systems can be lifted to the analysis of an equivalent auxiliary landscape of a closed composite system that contains the environmental interactions. This inherent connection can be analyzed to provide relevant information about the topology of the original open system landscape. Application to the optimization of an observable expectation value reveals the same landscape simplicity observed in former studies on closed systems. In particular, no false sub-optimal traps exist in the system control landscape when seeking to optimize an observable, even in the presence of complex environments. Moreover, a quantitative study of the control landscape of a system interacting with a thermal environment shows that the enhanced controllability attainable with open dynamics significantly broadens the range of the achievable observable values over the control landscape.
Computational costs of data definition at the quantum - classical interface
Chris Fields
2010-05-26
Model-independent semantic requirements for user specification and interpretation of data before and after quantum computations are characterized. Classical computational costs of assigning classical data values to quantum registers and to run-time parameters passed across a classical-to-quantum application programming interface are derived. It is shown that the classical computational costs of data definition equal or exceed the classical computational cost of solving the problem of interest for all applications of quantum computing except computations defined over the integers and the simulation of linear systems with linear boundary conditions.
Rebentrost, Patrick; Yuen-Zhou, Joel; Aspuru-Guzik, Alán
2010-01-01
Long-lived electronic coherences in various photosynthetic complexes at cryogenic and room temperature have generated vigorous efforts both in theory and experiment to understand their origins and explore their potential role to biological function. The ultrafast signals resulting from the experiments that show evidence for these coherences result from many contributions to the molecular polarization. Quantum process tomography (QPT) was conceived in the context of quantum information processing to characterize and understand general quantum evolution of controllable quantum systems, for example while carrying out quantum computational tasks. We introduce our QPT method for ultrafast experiments, and as an illustrative example, apply it to a simulation of a two-chromophore subsystem of the Fenna-Matthews-Olson photosynthetic complex, which was recently shown to have long-lived quantum coherences. Our Fenna-Matthews-Olson model is constructed using an atomistic approach to extract relevant parameters for the s...
Calgary, University of
ABSTRACT Oil and gas are global fuels obtained primarily from drilling wells in underground terrestrial reservoirs. Vertical drilling is preferred because of its simplicity and therefore low cost, but subsurfaceUCGE Reports Number 20284 Department of Geomatics Engineering Continuous Measurement-While-Drilling
Student Code Number: Thermodynamics
Feeny, Brian
Student Code Number: Thermodynamics Ph.D. Qualifying Exam Department of Mechanical Engineering;Thermodynamics Qualifier January 2013 Problem 1 Air is compressed in an axial-flow compressor operating at steady of exergy destruction within the compressor, in kJ per kg of air flowing. #12;Thermodynamics Qualifier
Calgary, University of
in considerable operational cost savings for many exploration and open-pit mining companies in the energy sectorUCGE Reports Number 20146 Department of Geomatics Engineering Development of a Mobile Equipment Equipment Management System solution. In the open-pit mining industries there is a need for these companies
Australia NO REGISTRATION NUMBER
Portugal Romania Slovenia Spain Turkey UK USA Australia Austria Belgium Cyprus France Germany Greece#12;#12;Australia Austria Belgium Cyprus France Germany Greece Ireland Italy Japan Macedonia Ireland Italy Japan Macedonia Portugal Romania Slovenia Spain Turkey UK USA #12;NO REGISTRATION NUMBER 1
Stapp, H.P.
1988-04-01
It is argued that the validity of the predictions of quantum theory in certain spin-correlation experiments entails a violation of Einstein's locality idea that no causal influence can act outside the forward light cone. First, two preliminary arguments suggesting such a violation are reviewed. They both depend, in intermediate stages, on the idea that the results of certain unperformed experiments are physically determinate. The second argument is entangled also with the problem of the meaning of physical reality. A new argument having neither of these characteristics is constructed. It is based strictly on the orthodox ideas of Bohr and Heisenberg, and has no realistic elements, or other ingredients, that are alien to orthodox quantum thinking.
Resonator-quantum well infrared photodetectors
Choi, K. K. Sun, J.; Olver, K.; Jhabvala, M. D.; Jhabvala, C. A.; Waczynski, A.
2013-11-11
We applied a recent electromagnetic model to design the resonator-quantum well infrared photodetector (R-QWIP). In this design, we used an array of rings as diffractive elements to diffract normal incident light into parallel propagation and used the pixel volume as a resonator to intensify the diffracted light. With a proper pixel size, the detector resonates at certain optical wavelengths and thus yields a high quantum efficiency (QE). To test this detector concept, we fabricated a number of R-QWIPs with different quantum well materials and detector geometries. The experimental result agrees satisfactorily with the prediction, and the highest QE achieved is 71%.
Heisenberg scaling in relativistic quantum metrology
Friis, Nicolai; Fuentes, Ivette; Dür, Wolfgang
2015-01-01
We address the issue of precisely estimating small parameters encoded in a general linear transformation of the modes of a bosonic quantum field. Such Bogoliubov transformations frequently appear in the context of quantum optics. We provide a recipe for computing the quantum Fisher information for arbitrary pure initial states. We show that the maximally achievable precision of estimation is inversely proportional to the squared average particle number, and that such Heisenberg scaling requires non-classical, but not necessarily entangled states. Our method further allows to quantify losses in precision arising from being able to monitor only finitely many modes, for which we identify a lower bound.
Quantum Vacuum Experiments Using High Intensity Lasers
Mattias Marklund; Joakim Lundin
2009-04-02
The quantum vacuum constitutes a fascinating medium of study, in particular since near-future laser facilities will be able to probe the nonlinear nature of this vacuum. There has been a large number of proposed tests of the low-energy, high intensity regime of quantum electrodynamics (QED) where the nonlinear aspects of the electromagnetic vacuum comes into play, and we will here give a short description of some of these. Such studies can shed light, not only on the validity of QED, but also on certain aspects of nonperturbative effects, and thus also give insights for quantum field theories in general.
Dynamical Objectivity in Quantum Brownian Motion
J. Tuziemski; J. K. Korbicz
2015-01-05
We analyze one of the fundamental models of decoherence and quantum-to-classical transition---Quantum Brownian Motion, and show formation of a, so called, spectrum broadcast structure. As recently shown, this is a specific structure of multi-partite quantum states responsible for appearance of classical objective features in quantum mechanics. Working in the limit of a very massive central system and in a weak-coupling regime, we derive a surprising time-evolving, rather than time-asymptotic, spectrum broadcast structure, leading to perceived objectivity of a state of motion. We do it for realistic, noisy random environment, modeled as a thermal bath, and present some generalization to arbitrary single-mode Gaussian states. We study numerically the formation of the spectrum broadcast structure as a function of the temperature, showing its certain noise-robustness.
Quantum Monte Carlo methods and lithium cluster properties
Owen, R.K.
1990-12-01
Properties of small lithium clusters with sizes ranging from n = 1 to 5 atoms were investigated using quantum Monte Carlo (QMC) methods. Cluster geometries were found from complete active space self consistent field (CASSCF) calculations. A detailed development of the QMC method leading to the variational QMC (V-QMC) and diffusion QMC (D-QMC) methods is shown. The many-body aspect of electron correlation is introduced into the QMC importance sampling electron-electron correlation functions by using density dependent parameters, and are shown to increase the amount of correlation energy obtained in V-QMC calculations. A detailed analysis of D-QMC time-step bias is made and is found to be at least linear with respect to the time-step. The D-QMC calculations determined the lithium cluster ionization potentials to be 0.1982(14) [0.1981], 0.1895(9) [0.1874(4)], 0.1530(34) [0.1599(73)], 0.1664(37) [0.1724(110)], 0.1613(43) [0.1675(110)] Hartrees for lithium clusters n = 1 through 5, respectively; in good agreement with experimental results shown in the brackets. Also, the binding energies per atom was computed to be 0.0177(8) [0.0203(12)], 0.0188(10) [0.0220(21)], 0.0247(8) [0.0310(12)], 0.0253(8) [0.0351(8)] Hartrees for lithium clusters n = 2 through 5, respectively. The lithium cluster one-electron density is shown to have charge concentrations corresponding to nonnuclear attractors. The overall shape of the electronic charge density also bears a remarkable similarity with the anisotropic harmonic oscillator model shape for the given number of valence electrons.
Quantum Monte Carlo methods and lithium cluster properties. [Atomic clusters
Owen, R.K.
1990-12-01
Properties of small lithium clusters with sizes ranging from n = 1 to 5 atoms were investigated using quantum Monte Carlo (QMC) methods. Cluster geometries were found from complete active space self consistent field (CASSCF) calculations. A detailed development of the QMC method leading to the variational QMC (V-QMC) and diffusion QMC (D-QMC) methods is shown. The many-body aspect of electron correlation is introduced into the QMC importance sampling electron-electron correlation functions by using density dependent parameters, and are shown to increase the amount of correlation energy obtained in V-QMC calculations. A detailed analysis of D-QMC time-step bias is made and is found to be at least linear with respect to the time-step. The D-QMC calculations determined the lithium cluster ionization potentials to be 0.1982(14) (0.1981), 0.1895(9) (0.1874(4)), 0.1530(34) (0.1599(73)), 0.1664(37) (0.1724(110)), 0.1613(43) (0.1675(110)) Hartrees for lithium clusters n = 1 through 5, respectively; in good agreement with experimental results shown in the brackets. Also, the binding energies per atom was computed to be 0.0177(8) (0.0203(12)), 0.0188(10) (0.0220(21)), 0.0247(8) (0.0310(12)), 0.0253(8) (0.0351(8)) Hartrees for lithium clusters n = 2 through 5, respectively. The lithium cluster one-electron density is shown to have charge concentrations corresponding to nonnuclear attractors. The overall shape of the electronic charge density also bears a remarkable similarity with the anisotropic harmonic oscillator model shape for the given number of valence electrons.
CONTROL OF NON-RESONANT EFFECTS IN A NUCLERA SPIN QUANTUM COMPUTER...
Office of Scientific and Technical Information (OSTI)
COMPUTER WITH A LARGE NUMBER OF QUBITS G. BERMAN; ET AL 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 99 GENERAL AND MISCELLANEOUSMATHEMATICS, COMPUTING, AND...
The Hausdorff dimension of fractal sets and fractional quantum Hall effect
Wellington da Cruz
2003-05-27
We consider Farey series of rational numbers in terms of {\\it fractal sets} labeled by the Hausdorff dimension with values defined in the interval 1$ $$ < $$ $$h$$ $$ <$$ $$ 2$ and associated with fractal curves. Our results come from the observation that the fractional quantum Hall effect-FQHE occurs in pairs of {\\it dual topological quantum numbers}, the filling factors. These quantum numbers obey some properties of the Farey series and so we obtain that {\\it the universality classes of the quantum Hall transitions are classified in terms of $h$}. The connection between Number Theory and Physics appears naturally in this context.
Jeongho Bang; James Lim; M. S. Kim; Jinhyoung Lee
2008-03-31
We propose a novel notion of a quantum learning machine for automatically controlling quantum coherence and for developing quantum algorithms. A quantum learning machine can be trained to learn a certain task with no a priori knowledge on its algorithm. As an example, it is demonstrated that the quantum learning machine learns Deutsch's task and finds itself a quantum algorithm, that is different from but equivalent to the original one.
Angular dependence of light trapping in In{sub 0.3}Ga{sub 0.7}As/GaAs quantum-well solar cells
Li, X. H.; Li, P. C.; Yu, E. T.; Hu, D. Z.; Schaadt, D. M.
2014-01-28
The dependence of light trapping effects in In{sub 0.3}Ga{sub 0.7}As/GaAs quantum-well solar cells on wavelength and incident angle is experimentally characterized and analyzed. Separation of active device layers from their epitaxial growth substrate enables integration of thin-film semiconductor device layers with nanostructured metal/dielectric rear contacts to increase optical absorption via coupling to both Fabry-Perot resonances and guided lateral propagation modes in the semiconductor. The roles of Fabry-Perot resonances and coupling to guided modes are analyzed via photocurrent response measurements and numerical modeling for light incident at angles of 0° (normal incidence) to 30° off normal. Light trapping enables external quantum efficiency at long wavelengths as high as 2.9% per quantum well to be achieved experimentally, substantially exceeding the ?1% per quantum well level typically observed. Increased long wavelength quantum efficiency is shown in experimental measurements to persist with increasing angle of incidence and is explained as a consequence of the large number of guided modes available in the device structure.
Naked singularities and quantum gravity
Harada, Tomohiro; Iguchi, Hideo; Nakao, Ken-ichi; Singh, T. P.; Tanaka, Takahiro; Vaz, Cenalo
2001-08-15
There are known models of spherical gravitational collapse in which the collapse ends in a naked shell-focusing singularity for some initial data. If a massless scalar field is quantized on the classical background provided by such a star, it is found that the outgoing quantum flux of the scalar field diverges in the approach to the Cauchy horizon. We argue that the semiclassical approximation (i.e., quantum field theory on a classical curved background) used in these analyses ceases to be valid about one Planck time before the epoch of naked singularity formation, because by then the curvature in the central region of the star reaches the Planck scale. It is shown that during the epoch in which the semiclassical approximation is valid, the total emitted energy is about one Planck unit, and is not divergent. We also argue that back reaction in this model does not become important so long as gravity can be treated classically. It follows that the further evolution of the star will be determined by quantum gravitational effects, and without invoking quantum gravity it is not possible to say whether the star radiates away on a short time scale or settles down into a black hole state.
F. Benatti; M. Fannes
1998-11-26
We use multi-time correlation functions of quantum systems to construct random variables with statistical properties that reflect the degree of complexity of the underlying quantum dynamics.
Quantum Optimal Control Theory
G. H. Gadiyar
1994-05-10
The possibility of control of phenomena at microscopic level compatible with quantum mechanics and quantum field theory is outlined. The theory could be used in nanotechnology.
H. J. Kimble
2008-06-25
Quantum networks offer a unifying set of opportunities and challenges across exciting intellectual and technical frontiers, including for quantum computation, communication, and metrology. The realization of quantum networks composed of many nodes and channels requires new scientific capabilities for the generation and characterization of quantum coherence and entanglement. Fundamental to this endeavor are quantum interconnects that convert quantum states from one physical system to those of another in a reversible fashion. Such quantum connectivity for networks can be achieved by optical interactions of single photons and atoms, thereby enabling entanglement distribution and quantum teleportation between nodes.
Paul Benioff
2015-08-07
The relationship between the foundations of mathematics and physics is a topic of of much interest. This paper continues this exploration by examination of the effect of space and time dependent number scaling on theoretical descriptions of some physical and geometric quantities. Fiber bundles provide a good framework to introduce a space and time or space time dependent number scaling field. The effect of the scaling field on a few nonlocal physical and geometric quantities is described. The effect on gauge theories is to introduce a new complex scalar field into the derivatives appearing in Lagrangians. U(1) invariance of Lagrangian terms does not affect the real part of the scaling field. For this field, any mass is possible. The scaling field is also shown to affect quantum wave packets and path lengths, and geodesic equations even on flat space. Scalar fields described so far in physics, are possible candidates for the scaling field. The lack of direct evidence for the field in physics restricts the scaling field in that the gradient of the field must be close to zero in a local region of cosmological space and time. There are no restrictions outside the region. It is also seen that the scaling field does not affect comparisons of computation or measurements outputs with one another. However it does affect the assignment of numerical values to the outputs of computations or measurements. These are needed because theory predictions are in terms of numerical values.
Entropy and Area of Black Holes in Loop Quantum Gravity
I. B. Khriplovich
2002-03-31
Simple arguments related to the entropy of black holes strongly constrain the spectrum of the area operator for a Schwarzschild black hole in loop quantum gravity. In particular, this spectrum is fixed completely by the assumption that the black hole entropy is maximum. Within the approach discussed, one arrives in loop quantum gravity at a quantization rule with integer quantum numbers $n$ for the entropy and area of a black hole.
Extractable work from ensembles of quantum batteries. Entanglement helps
Robert Alicki; Mark Fannes
2012-11-19
Motivated by the recent interest in thermodynamics of micro- and mesoscopic quantum systems we study the maximal amount of work that can be reversibly extracted from a quantum system used to store temporarily energy. Guided by the notion of passivity of a quantum state we show that entangling unitary controls extract in general more work than independent ones. In the limit of large number of copies one can reach the thermodynamical bound given by the variational principle for free energy.
Optimisation of Quantum Evolution Algorithms
Apoorva Patel
2015-03-04
Given a quantum Hamiltonian and its evolution time, the corresponding unitary evolution operator can be constructed in many different ways, corresponding to different trajectories between the desired end-points. A choice among these trajectories can then be made to obtain the best computational complexity and control over errors. As an explicit example, Grover's quantum search algorithm is described as a Hamiltonian evolution problem. It is shown that the computational complexity has a power-law dependence on error when a straightforward Lie-Trotter discretisation formula is used, and it becomes logarithmic in error when reflection operators are used. The exponential change in error control is striking, and can be used to improve many importance sampling methods. The key concept is to make the evolution steps as large as possible while obeying the constraints of the problem. In particular, we can understand why overrelaxation algorithms are superior to small step size algorithms.
Alternative quantization of the Hamiltonian in isotropic loop quantum cosmology
Jinsong Yang; You Ding; Yongge Ma
2009-04-28
Since there are quantization ambiguities in constructing the Hamiltonian constraint operator in isotropic loop quantum cosmology, it is crucial to check whether the key features of loop quantum cosmology, such as the quantum bounce and effective scenario, are robust against the ambiguities. In this paper, we consider a typical quantization ambiguity arising from the quantization of the field strength of the gravitational connection. An alternative Hamiltonian constraint operator is constructed, which is shown to have the correct classical limit by the semiclassical analysis. The effective Hamiltonian incorporating higher order quantum corrections is also obtained. In the spatially flat FRW model with a massless scalar field, the classical big bang is again replaced by a quantum bounce. Moreover, there are still great possibilities for the expanding universe to recollapse due to the quantum gravity effect. Thus, these key features are robust against this quantization ambiguity.
Stránský, Pavel; Macek, Michal; Cejnar, Pavel
2014-06-15
Quantum systems with a finite number of freedom degrees f develop robust singularities in the energy spectrum of excited states as the system’s size increases to infinity. We analyze the general form of these singularities for low f, particularly f=2, clarifying the relation to classical stationary points of the corresponding potential. Signatures in the smoothed energy dependence of the quantum state density and in the flow of energy levels with an arbitrary control parameter are described along with the relevant thermodynamical consequences. The general analysis is illustrated with specific examples of excited-state singularities accompanying the first-order quantum phase transition. -- Highlights: •ESQPTs found in infinite-size limit of systems with low numbers of freedom degrees f. •ESQPTs related to non-analytical evolutions of classical phase–space properties. •ESQPT signatures analyzed for general f, particularly f=2, extending known case f=1. •ESQPT signatures identified in smoothened density and flow of energy spectrum. •ESQPTs shown to induce a new type of thermodynamic anomalies.
The quantum character of physical fields. Foundations of field theories
L. I. Petrova
2006-03-15
The existing field theories are based on the properties of closed exterior forms, which are invariant ones and correspond to conservation laws for physical fields. Hence, to understand the foundations of field theories and their unity, one has to know how such closed exterior forms are obtained. In the present paper it is shown that closed exterior forms corresponding to field theories are obtained from the equations modelling conservation (balance)laws for material media. It has been developed the evolutionary method that enables one to describe the process of obtaining closed exterior forms. The process of obtaining closed exterior forms discloses the mechanism of evolutionary processes in material media and shows that material media generate, discretely, the physical structures, from which the physical fields are formed. This justifies the quantum character of field theories. On the other hand, this process demonstrates the connection between field theories and the equations for material media and points to the fact that the foundations of field theories must be conditioned by the properties of material media. It is shown that the external and internal symmetries of field theories are conditioned by the degrees of freedom of material media. The classification parameter of physical fields and interactions, that is, the parameter of the unified field theory, is connected with the number of noncommutative balance conservation laws for material media.
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Quantum Interference Induced Photon Blockade in a Coupled Single Quantum Dot-Cavity System
Jing Tang; Weidong Geng; Xiulai Xu
2015-03-18
We propose an experimental scheme to implement a strong photon blockade with a single quantum dot coupled to a nanocavity. The photon blockade effect can be tremendously enhanced by driving the cavity and the quantum dot simultaneously with two classical laser fields. This enhancement of photon blockade is ascribed to the quantum interference effect to avoid two-photon excitation of the cavity field. Comparing with Jaynes-Cummings model, the second-order correlation function at zero time delay $g^{(2)}(0)$ in our scheme can be reduced by two orders of magnitude and the system sustains a large intracavity photon number. A red (blue) cavity-light detuning asymmetry for photon quantum statistics with bunching or antibunching characteristics is also observed. The photon blockade effect has a controllable flexibility by tuning the relative phase between the two pumping laser fields and the Rabi coupling strength between the quantum dot and the pumping field. Moreover, the photon blockade scheme based on quantum interference mechanism does not require a strong coupling strength between the cavity and the quantum dot, even with the pure dephasing of the system. This simple proposal provides an effective way for potential applications in solid state quantum computation and quantum information processing.
Architecture for a large-scale ion-trap quantum computer
Monroe, Christopher
Architecture for a large-scale ion-trap quantum computer D. Kielpinski*, C. Monroe & D. J. Wineland ........................................................................................................................................................................................................................... Among the numerous types of architecture being explored for quantum computers are systems utilizing ion proposed a `quantum charge-coupled device' (QCCD) architecture consisting of a large number
Quantum chaos in the nuclear collective model: I. Classical-quantum correspondence
Pavel Stransky; Petr Hruska; Pavel Cejnar
2009-02-23
Spectra of the geometric collective model of atomic nuclei are analyzed to identify chaotic correlations among nonrotational states. The model has been previously shown to exhibit a high degree of variability of regular and chaotic classical features with energy and control parameters. Corresponding signatures are now verified also on the quantum level for different schemes of quantization and with a variable classicality constant.
Topological color codes and two-body quantum lattice Hamiltonians
Kargarian, M.
Topological color codes are among the stabilizer codes with remarkable properties from the quantum information perspective. In this paper, we construct a lattice, the so-called ruby lattice, with coordination number 4 ...
Localized quantum walks as secured quantum memory
C. M. Chandrashekar; Th. Busch
2015-04-21
We show that a quantum walk process can be used to construct and secure quantum memory. More precisely, we show that a localized quantum walk with temporal disorder can be engineered to store the information of a single, unknown qubit on a compact position space and faithfully recover it on demand. Since the localization occurss with a finite spread in position space, the stored information of the qubit will be naturally secured from the simple eavesdropper. Our protocol can be adopted to any quantum system for which experimental control over quantum walk dynamics can be achieved.
Hybrid quantum devices and quantum engineering
Margareta Wallquist; Klemens Hammerer; Peter Rabl; Mikhail Lukin; Peter Zoller
2009-11-19
We discuss prospects of building hybrid quantum devices involving elements of atomic and molecular physics, quantum optics and solid state elements with the attempt to combine advantages of the respective systems in compatible experimental setups. In particular, we summarize our recent work on quantum hybrid devices and briefly discuss recent ideas for quantum networks. These include interfacing of molecular quantum memory with circuit QED, and using nanomechanical elements strongly coupled to qubits represented by electronic spins, as well as single atoms or atomic ensembles.
Quantum Annealing and Analog Quantum Computation
Arnab Das; Bikas K. Chakrabarti
2008-03-24
We review here the recent success in quantum annealing, i.e., optimization of the cost or energy functions of complex systems utilizing quantum fluctuations. The concept is introduced in successive steps through the studies of mapping of such computationally hard problems to the classical spin glass problems. The quantum spin glass problems arise with the introduction of quantum fluctuations, and the annealing behavior of the systems as these fluctuations are reduced slowly to zero. This provides a general framework for realizing analog quantum computation.
On Some Zarankiewicz Numbers and Bipartite Ramsey Numbers for
Radziszowski, Stanislaw P.
On Some Zarankiewicz Numbers and Bipartite Ramsey Numbers for Quadrilateral Janusz Dybizba Ramsey number b(n1, Â· Â· Â· , nk) is the least positive integer b such that any coloring of the edges of Kb Ramsey numbers avoiding quadrilateral. In particular, we prove that b4(2) = 19, and establish new general
The quantum cryptographic switch
Srinatha Narayanaswamy; Omkar Srikrishna; R. Srikanth; Subhashish Banerjee; Anirban Pathak
2011-11-21
We illustrate using a quantum system the principle of a cryptographic switch, in which a third party (Charlie) can control to a continuously varying degree the amount of information the receiver (Bob) receives, after the sender (Alice) has sent her information. Suppose Charlie transmits a Bell state to Alice and Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit information corresponding to choice of Bell state is made available by Charlie to Bob can the latter recover Alice's information. By varying the information he gives, Charlie can continuously vary the information recovered by Bob. The performance of the protocol subjected to the squeezed generalized amplitude damping channel is considered. We also present a number of practical situations where a cryptographic switch would be of use.
Azhar Iqbal; Derek Abbott
2008-10-21
A quantum version of the Matching Pennies (MP) game is proposed that is played using an Einstein-Podolsky-Rosen-Bohm (EPR-Bohm) setting. We construct the quantum game without using the state vectors, while considering only the quantum mechanical joint probabilities relevant to the EPR-Bohm setting. We embed the classical game within the quantum game such that the classical MP game results when the quantum mechanical joint probabilities become factorizable. We report new Nash equilibria in the quantum MP game that emerge when the quantum mechanical joint probabilities maximally violate the Clauser-Horne-Shimony-Holt form of Bell's inequality.
Quantum Kolmogorov Complexity and the Quantum Turing Machine
Markus Mueller
2007-12-28
The purpose of this thesis is to give a formal definition of quantum Kolmogorov complexity (QC), and rigorous mathematical proofs of its basic properties. The definition used here is similar to that by Berthiaume, van Dam, and Laplante. It defines the QC of some indeterminate-length qubit string \\rho as the minimum base length of any quantum input which makes a quantum Turing machine (QTM) halt and output \\rho, up to some error tolerance. First, we prove that there is a QTM which is universal in the sense of input base length. Furthermore, we show several general properties of QTMs, including a result on mutually orthogonal ``halting spaces'', and a way to transform every almost-halting input into a deterministically-halting input by adding at most a constant number of qubits. Afterwards, we apply these results to QC. In particular, we show that QC is invariant, incompressible, agrees with classical Kolmogorov complexity for classical strings, and is closely related to von Neumann entropy for ergodic quantum information sources.
Confining Backgrounds and Quantum Chaos in Holography
Basu, Pallab
2013-01-01
Classical world-sheet string theory has recently been shown to be nonintegrable and chaotic in various confining string theory backgrounds -- the AdS soliton background in particular. In this paper we study a minisuperspace quantization of the theory and look at properties of the spectrum like the distribution of level spacing, which are indicative of quantum order or chaos. In the quantum spectrum we find a gradual transition from chaotic (Wigner GOE) to integrable (Poisson) regime as we look at higher energies. This is expected since our system is integrable asymptotically, and at higher energies, the dynamics is entirely dominated by the kinetic terms.
Bilinear covariants and spinor fields duality in quantum Clifford algebras
Ab?amowicz, Rafa?; Gonçalves, Icaro; Rocha, Roldão da
2014-10-15
Classification of quantum spinor fields according to quantum bilinear covariants is introduced in a context of quantum Clifford algebras on Minkowski spacetime. Once the bilinear covariants are expressed in terms of algebraic spinor fields, the duality between spinor and quantum spinor fields can be discussed. Thus, by endowing the underlying spacetime with an arbitrary bilinear form with an antisymmetric part in addition to a symmetric spacetime metric, quantum algebraic spinor fields and deformed bilinear covariants can be constructed. They are thus compared to the classical (non quantum) ones. Classes of quantum spinor fields classes are introduced and compared with Lounesto's spinor field classification. A physical interpretation of the deformed parts and the underlying Z-grading is proposed. The existence of an arbitrary bilinear form endowing the spacetime already has been explored in the literature in the context of quantum gravity [S. W. Hawking, “The unpredictability of quantum gravity,” Commun. Math. Phys. 87, 395 (1982)]. Here, it is shown further to play a prominent role in the structure of Dirac, Weyl, and Majorana spinor fields, besides the most general flagpoles and flag-dipoles. We introduce a new duality between the standard and the quantum spinor fields, by showing that when Clifford algebras over vector spaces endowed with an arbitrary bilinear form are taken into account, a mixture among the classes does occur. Consequently, novel features regarding the spinor fields can be derived.
Hybrid Quantum Cloning Machine
Satyabrata Adhikari; A. K. Pati; Indranil Chakrabarty; B. S. Choudhury
2007-06-14
In this work, we introduce a special kind of quantum cloning machine called Hybrid quantum cloning machine. The introduced Hybrid quantum cloning machine or transformation is nothing but a combination of pre-existing quantum cloning transformations. In this sense it creates its own identity in the field of quantum cloners. Hybrid quantum cloning machine can be of two types: (i) State dependent and (ii) State independent or Universal. We study here the above two types of Hybrid quantum cloning machines. Later we will show that the state dependent hybrid quantum-cloning machine can be applied on only four input states. We will also find in this paper another asymmetric universal quantum cloning machine constructed from the combination of optimal universal B-H quantum cloning machine and universal anti-cloning machine. The fidelities of the two outputs are different and their values lie in the neighborhood of ${5/6} $
The Learnability of Unknown Quantum Measurements
Hao-Chung Cheng; Min-Hsiu Hsieh; Ping-Cheng Yeh
2015-01-03
Quantum machine learning has received significant attention in recent years, and promising progress has been made in the development of quantum algorithms to speed up traditional machine learning tasks. In this work, however, we focus on investigating the information-theoretic upper bounds of sample complexity - how many training samples are sufficient to predict the future behaviour of an unknown target function. This kind of problem is, arguably, one of the most fundamental problems in statistical learning theory and the bounds for practical settings can be completely characterised by a simple measure of complexity. Our main result in the paper is that, for learning an unknown quantum measurement, the upper bound, given by the fat-shattering dimension, is linearly proportional to the dimension of the underlying Hilbert space. Learning an unknown quantum state becomes a dual problem to ours, and as a byproduct, we can recover Aaronson's famous result [Proc. R. Soc. A 463:3089-3144 (2007)] solely using a classical machine learning technique. In addition, other famous complexity measures like covering numbers and Rademacher complexities are derived explicitly. We are able to connect measures of sample complexity with various areas in quantum information science, e.g. quantum state/measurement tomography, quantum state discrimination and quantum random access codes, which may be of independent interest. Lastly, with the assistance of general Bloch-sphere representation, we show that learning quantum measurements/states can be mathematically formulated as a neural network. Consequently, classical ML algorithms can be applied to efficiently accomplish the two quantum learning tasks.
Automated Search for new Quantum Experiments
Mario Krenn; Mehul Malik; Robert Fickler; Radek Lapkiewicz; Anton Zeilinger
2015-09-09
Quantum mechanics predicts a number of at first sight counterintuitive phenomena. It is therefore a question whether our intuition is the best way to find new experiments. Here we report the development of the computer algorithm Melvin which is able to find new experimental implementations for the creation and manipulation of complex quantum states. And indeed, the discovered experiments extensively use unfamiliar and asymmetric techniques which are challenging to understand intuitively. The results range from the first implementation of a high-dimensional Greenberger-Horne-Zeilinger (GHZ) state, to a vast variety of experiments for asymmetrically entangled quantum states - a feature that can only exist when both the number of involved parties and dimensions is larger than 2. Additionally, new types of high-dimensional transformations are found that perform cyclic operations. Melvin autonomously learns from solutions for simpler systems, which significantly speeds up the discovery rate of more complex experiments. The ability to automate the design of a quantum experiment can be applied to many quantum systems and allows the physical realization of quantum states previously thought of only on paper.
Universal simulation of Markovian open quantum systems
Ryan Sweke; Ilya Sinayskiy; Denis Bernard; Francesco Petruccione
2015-07-02
We consider the problem of constructing a "universal set" of Markovian processes, such that any Markovian open quantum system, described by a one-parameter semigroup of quantum channels, can be simulated through sequential simulations of processes from the universal set. In particular, for quantum systems of dimension $d$, we explicitly construct a universal set of semigroup generators, parametrized by $d^2-3$ continuous parameters, and prove that a necessary and sufficient condition for the dynamical simulation of a $d$ dimensional Markovian quantum system is the ability to implement a) quantum channels from the semigroups generated by elements of the universal set of generators, and b) unitary operations on the system. Furthermore, we provide an explicit algorithm for simulating the dynamics of a Markovian open quantum system using this universal set of generators, and show that it is efficient, with respect to this universal set, when the number of distinct Lindblad operators (representing physical dissipation processes) scales polynomially with respect to the number of subsystems.
Slow phase relaxation as a route to quantum computing beyond the quantum chaos border
Flores, J.; Seligman, T.H. [Centro de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos (Mexico); Kun, S.Yu. [Centro de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos (Mexico); Centre for Nonlinear Physics, RSPhysSE, ANU, Canberra ACT 0200 (Australia); Department of Theoretical Physics, RSPhysSE, ANU, Canberra ACT 0200 (Australia)
2005-07-01
We reveal that phase memory can be much longer than energy relaxation in systems with exponentially large dimensions of Hilbert space; this finding is documented by 50 years of nuclear experiments, though the information is somewhat hidden. For quantum computers Hilbert spaces of dimension 2{sup 100} or larger will be typical and therefore this effect may contribute significantly to reduce the problems of scaling of quantum computers to a useful number of qubits.
Quantum Thermodynamic Cycles and quantum heat engines
H. T. Quan; Yu-xi Liu; C. P. Sun; Franco Nori
2007-04-03
In order to describe quantum heat engines, here we systematically study isothermal and isochoric processes for quantum thermodynamic cycles. Based on these results the quantum versions of both the Carnot heat engine and the Otto heat engine are defined without ambiguities. We also study the properties of quantum Carnot and Otto heat engines in comparison with their classical counterparts. Relations and mappings between these two quantum heat engines are also investigated by considering their respective quantum thermodynamic processes. In addition, we discuss the role of Maxwell's demon in quantum thermodynamic cycles. We find that there is no violation of the second law, even in the existence of such a demon, when the demon is included correctly as part of the working substance of the heat engine.
Stefan Völk; Florian J. R. Schülein; Florian Knall; Dirk Reuter; Andreas D. Wieck; Tuan A. Truong; Hyochul Kim; Pierre M. Petroff; Achim Wixforth; Hubert J. Krenner
2010-11-19
Individual self-assembled Quantum Dots and Quantum Posts are studied under the influence of a surface acoustic wave. In optical experiments we observe an acoustically induced switching of the occupancy of the nanostructures along with an overall increase of the emission intensity. For Quantum Posts, switching occurs continuously from predominantely charged excitons (dissimilar number of electrons and holes) to neutral excitons (same number of electrons and holes) and is independent on whether the surface acoustic wave amplitude is increased or decreased. For quantum dots, switching is non-monotonic and shows a pronounced hysteresis on the amplitude sweep direction. Moreover, emission of positively charged and neutral excitons is observed at high surface acoustic wave amplitudes. These findings are explained by carrier trapping and localization in the thin and disordered two-dimensional wetting layer on top of which Quantum Dots nucleate. This limitation can be overcome for Quantum Posts where acoustically induced charge transport is highly efficient in a wide lateral Matrix-Quantum Well.
A reconfigurable spintronic device for quantum and classical logic
Debanjan Bhowmik; Aamod Shanker; Angik Sarkar; Tarun Kanti Bhattacharyya
2010-12-09
Quantum superposition and entanglement of physical states can be harnessed to solve some problems which are intractable on a classical computer implementing binary logic. Several algorithms have been proposed to utilize the quantum nature of physical states and solve important problems. For example, Shor's quantum algorithm is extremely important in the field of cryptography since it factors large numbers exponentially faster than any known classical algorithm. Another celebrated example is the Grovers quantum algorithm. These algorithms can only be implemented on a quantum computer which operates on quantum bits (qubits). Rudimentary implementations of quantum processor have already been achieved through linear optical components, ion traps, NMR etc. However demonstration of a solid state quantum processor had been elusive till DiCarlo et al demonstrated two qubit algorithms in superconducting quantum processor. Though this has been a significant step, scalable semiconductor based room temperature quantum computing is yet to be found. Such a technology could benefit from the vast experience of the semiconductor industry. Hence, here we present a reconfigurable semiconductor quantum logic device (SQuaLD) which operates on the position and spin degree of freedom of the electrons in the device. Based on a few recent experiments, we believe SQuaLD is experimentally feasible. Moreover, using a well known quantum simulation method, we show that quantum algorithms (such as Deutsch Jozsa, Grover search) as well as universal classical logic operations (such as NAND gate) can be implemented in SQuaLD. Thus, we argue that SQuaLD is a strong candidate for the future quantum logic processor since it also satisfies the DiVincenzo criteria for quantum logic application as well as the five essential characteristics for classical logic applications.
A quantum speedup in machine learning: Finding a N-bit Boolean function for a classification
Seokwon Yoo; Jeongho Bang; Changhyoup Lee; Jinhyoung Lee
2014-10-14
We compare quantum and classical machines designed for learning an N-bit Boolean function in order to address how a quantum system improves the machine learning behavior. The machines of the two types consist of the same number of operations and control parameters, but only the quantum machines utilize the quantum coherence naturally induced by unitary operators. We show that quantum superposition enables quantum learning that is faster than classical learning by expanding the approximate solution regions, i.e., the acceptable regions. This is also demonstrated by means of numerical simulations with a standard feedback model, namely random search, and a practical model, namely differential evolution.
Infinite Quantum Group Symmetry of Fields in Massive 2D Quantum Field Theory
A. LeCLair; F. Smirnov
1991-08-20
Starting from a given S-matrix of an integrable quantum field theory in $1+1$ dimensions, and knowledge of its on-shell quantum group symmetries, we describe how to extend the symmetry to the space of fields. This is accomplished by introducing an adjoint action of the symmetry generators on fields, and specifying the form factors of descendents. The braiding relations of quantum field multiplets is shown to be given by the universal $\\CR$-matrix. We develop in some detail the case of infinite dimensional Yangian symmetry. We show that the quantum double of the Yangian is a Hopf algebra deformation of a level zero Kac-Moody algebra that preserves its finite dimensional Lie subalgebra. The fields form infinite dimensional Verma-module representations; in particular the energy-momentum tensor and isotopic current are in the same multiplet.
Communication via entangled coherent quantum network
A. El Allati; Y. Hassouni; N. Metwally
2010-11-17
A quantum network is constructed via maximum entangled coherent states. The possibility of using this network to achieve communication between multi-participants is investigated. We showed that the probability of teleported unknown state successfully, depends on the size the used network. As the numbers of participants increases, the successful probability does not depend on the intensity of the field. The problem of implementing quantum teleportation protocol via a noise quantum network is discussed. We show one can send information perfectly with small values of the field intensity and larger values of the noise strength. The successful probability of this suggested protocol increases abruptly for larger values of the noise strength and gradually for small values. We show that for small size of the used quantum network, the fidelity of the teleported state decreases smoothly, while it decreases abruptly for larger size of network.
Time-Energy Costs of Quantum Measurements
Chi-Hang Fred Fung; H. F. Chau
2014-05-08
Time and energy of quantum processes are a tradeoff against each other. We propose to ascribe to any given quantum process a time-energy cost to quantify how much computation it performs. Here, we analyze the time-energy costs for general quantum measurements, along a similar line as our previous work for quantum channels, and prove exact and lower bound formulae for the costs. We use these formulae to evaluate the efficiencies of actual measurement implementations. We find that one implementation for a Bell measurement is optimal in time-energy. We also analyze the time-energy cost for unambiguous state discrimination and find evidence that only a finite time-energy cost is needed to distinguish any number of states.
Nuclear Physics from Lattice Quantum Chromodynamics
Savage, Martin J
2015-01-01
Quantum Chromodynamics and Quantum Electrodynamics, both renormalizable quantum field theories with a small number of precisely constrained input parameters, dominate the dynamics of the quarks and gluons - the underlying building blocks of protons, neutrons, and nuclei. While the analytic techniques of quantum field theory have played a key role in understanding the dynamics of matter in high energy processes, they encounter difficulties when applied to low-energy nuclear structure and reactions, and dense systems. Expected increases in computational resources into the exascale during the next decade will provide the ability to determine a range of important strong interaction processes directly from QCD using the numerical technique of Lattice QCD. This will complement the nuclear physics experimental program, and in partnership with new thrusts in nuclear many-body theory, will enable unprecedented understanding and refinement of nuclear forces and, more generally, the visible matter in our universe. In th...
Deviation from the Knudsen law on quantum gases
Babac, Gulru
2014-12-09
Gas flow in micro/nano scale systems has been generally studied for the Maxwell gases. In the limits of very low temperature and very confined domains, the Maxwellian approximation can break down and the quantum character of the gases becomes important. In these cases, Knudsen law, which is one of the important equations to analyze rarefied gas flows is invalid and should be reanalyzed for quantum gases. In this work, the availability of quantum gas conditions in the high Knudsen number cases is discussed and Knudsen law is analyzed for quantum gases.
A Performance Estimator for Quantum Annealers: Gauge selection and Parameter Setting
Alejandro Perdomo-Ortiz; Joseph Fluegemann; Rupak Biswas; Vadim N. Smelyanskiy
2015-03-03
With the advent of large-scale quantum annealing devices, several challenges have emerged. For example, it has been shown that the performance of a device can be significantly affected by several degrees of freedom when programming the device; a common example being gauge selection. To date, no experimentally-tested strategy exists to select the best programming specifications. We developed a score function that can be calculated from a number of readouts much smaller than the number of readouts required to find the desired solution. We show how this performance estimator can be used to guide, for example, the selection of the optimal gauges out of a pool of random gauge candidates and how to select the values of parameters for which we have no a priori knowledge of the optimal value. For the latter, we illustrate the concept by applying the score function to set the strength of the parameter intended to enforce the embedding of the logical graph into the hardware architecture, a challenge frequently encountered in the implementation of real-world problem instances. Since the harder the problem instances, the more useful the strategies proposed in this work are, we expect the programming strategies proposed to significantly reduce the time of future benchmark studies and in help finding the solution of hard-to-solve real-world applications implemented in the next generation of quantum annealing devices.
Photoconductivity of Si/Ge multilayer structures with Ge quantum dots pseudomorphic to the Si matrix
Talochkin, A. B., E-mail: tal@thermo.isp.nsc.ru; Chistokhin, I. B. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)
2011-07-15
Longitudinal photoconductivity spectra of Si/Ge multilayer structures with Ge quantum dots grown pseudomorphically to the Si matrix are studied. Lines of optical transitions between hole levels of quantum dots and Si electronic states are observed. This allowed us to construct a detailed energy-level diagram of electron-hole levels of the structure. It is shown that hole levels of pseudomorphic Ge quantum dots are well described by the simplest 'quantum box' model using actual sizes of Ge islands. The possibility of controlling the position of the long-wavelength photosensitivity edge by varying the growth parameters of Si/Ge structures with Ge quantum dots is determined.
Automated Search for new Quantum Experiments
Krenn, Mario; Fickler, Robert; Lapkiewicz, Radek; Zeilinger, Anton
2015-01-01
Quantum mechanics predicts a number of at first sight counterintuitive phenomena. It is therefore a question whether our intuition is the best way to find new experiments. Here we report the development of the computer algorithm Melvin which is able to find new experimental implementations for the creation and manipulation of complex quantum states. And indeed, the discovered experiments extensively use unfamiliar and asymmetric techniques which are challenging to understand intuitively. The results range from the first implementation of a high-dimensional Greenberger-Horne-Zeilinger (GHZ) state, to a vast variety of experiments for asymmetrically entangled quantum states - a feature that can only exist when both the number of involved parties and dimensions is larger than 2. Additionally, new types of high-dimensional transformations are found that perform cyclic operations. Melvin autonomously learns from solutions for simpler systems, which significantly speeds up the discovery rate of more complex experim...
Association of scattering matrices in quantum networks
Almeida, F.A.G.; Macêdo, A.M.S.
2013-06-15
Algorithms based on operations that associate scattering matrices in series or in parallel (analogous to impedance association in a classical circuit) are developed here. We exemplify their application by calculating the total scattering matrix of several types of quantum networks, such as star graphs and a chain of chaotic quantum dots, obtaining results with good agreement with the literature. Through a computational-time analysis we compare the efficiency of two algorithms for the simulation of a chain of chaotic quantum dots based on series association operations of (i) two-by-two centers and (ii) three-by-three ones. Empirical results point out that the algorithm (ii) is more efficient than (i) for small number of open scattering channels. A direct counting of floating point operations justifies quantitatively the superiority of the algorithm (i) for large number of open scattering channels.
Ryo Namiki; Masato Koashi; Nobuyuki Imoto
2008-08-11
We generalize the experimental success criterion for quantum teleportation/memory in continuous-variable quantum systems to be suitable for non-unit-gain condition by considering attenuation/amplification of the coherent-state amplitude. The new criterion can be used for a non-ideal quantum memory and long distance quantum communication as well as quantum devices with amplification process. It is also shown that the framework to measure the average fidelity is capable of detecting all Gaussian channels in quantum domain.
Quantum correlations, quantum resource theories and exclusion game
Liu, Zi-Wen
2015-01-01
This thesis addresses two topics in quantum information theory. The first topic is quantum correlations and quantum resource theory. The second is quantum communication theory. The first part summarizes an ongoing work ...
Magic State Distillation and Gate Compilation in Quantum Algorithms for Quantum Chemistry
Colin J. Trout; Kenneth R. Brown
2015-01-29
Quantum algorithms for quantum chemistry map the dynamics of electrons in a molecule to the dynamics of a coupled spin system. To reach chemical accuracy for interesting molecules, a large number of quantum gates must be applied which implies the need for quantum error correction and fault-tolerant quantum computation. Arbitrary fault-tolerant operations can be constructed from a small, universal set of fault-tolerant operations by gate compilation. Quantum chemistry algorithms are compiled by decomposing the dynamics of the coupled spin-system using a Trotter formula, synthesizing the decomposed dynamics using Clifford operations and single-qubit rotations, and finally approximating the single-qubit rotations by a sequence of fault-tolerant single-qubit gates. Certain fault-tolerant gates rely on the preparation of specific single-qubit states referred to as magic states. As a result, gate compilation and magic state distillation are critical for solving quantum chemistry problems on a quantum computer. We review recent progress that has improved the efficiency of gate compilation and magic state distillation by orders of magnitude.
On the power quantum computation over real Hilbert spaces
Matthew McKague
2015-10-12
We consider the power of various quantum complexity classes with the restriction that states and operators are defined over a real, rather than complex, Hilbert space. It is well know that a quantum circuit over the complex numbers can be transformed into a quantum circuit over the real numbers with the addition of a single qubit. This implies that BQP retains its power when restricted to using states and operations over the reals. We show that the same is true for QMA(k), QIP(k), QMIP, and QSZK.
Asymptotically Optimal Quantum Circuits for d-Level Systems
Bullock, Stephen S. [Mathematical and Computational Sciences Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8910 (United States); O'Leary, Dianne P. [Mathematical and Computational Sciences Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8910 (United States); Department of Computer Science and UMIACS, University of Maryland, College Park, Maryland 20742 (United States); Brennen, Gavin K. [Atomic Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8420 (United States)
2005-06-17
Scalability of a quantum computation requires that the information be processed on multiple subsystems. However, it is unclear how the complexity of a quantum algorithm, quantified by the number of entangling gates, depends on the subsystem size. We examine the quantum circuit complexity for exactly universal computation on many d-level systems (qudits). Both a lower bound and a constructive upper bound on the number of two-qudit gates result, proving a sharp asymptotic of {theta}(d{sup 2n}) gates. This closes the complexity question for all d-level systems (d finite). The optimal asymptotic applies to systems with locality constraints, e.g., nearest neighbor interactions.
Passive decoy state quantum key distribution with practical light sources
Marcos Curty; Xiongfeng Ma; Bing Qi; Tobias Moroder
2009-11-14
Decoy states have been proven to be a very useful method for significantly enhancing the performance of quantum key distribution systems with practical light sources. While active modulation of the intensity of the laser pulses is an effective way of preparing decoy states in principle, in practice passive preparation might be desirable in some scenarios. Typical passive schemes involve parametric down-conversion. More recently, it has been shown that phase randomized weak coherent pulses (WCP) can also be used for the same purpose [M. Curty {\\it et al.}, Opt. Lett. {\\bf 34}, 3238 (2009).] This proposal requires only linear optics together with a simple threshold photon detector, which shows the practical feasibility of the method. Most importantly, the resulting secret key rate is comparable to the one delivered by an active decoy state setup with an infinite number of decoy settings. In this paper we extend these results, now showing specifically the analysis for other practical scenarios with different light sources and photo-detectors. In particular, we consider sources emitting thermal states, phase randomized WCP, and strong coherent light in combination with several types of photo-detectors, like, for instance, threshold photon detectors, photon number resolving detectors, and classical photo-detectors. Our analysis includes as well the effect that detection inefficiencies and noise in the form of dark counts shown by current threshold detectors might have on the final secret ket rate. Moreover, we provide estimations on the effects that statistical fluctuations due to a finite data size can have in practical implementations.
Advances in Quantum Teleportation
Pirandola, Stefano; Weedbrook, Christian; Furusawa, Akira; Braunstein, Samuel L
2015-01-01
Quantum teleportation is one of the most important protocols in quantum information. By exploiting the physical resource of entanglement, quantum teleportation serves as a key primitive in a variety of quantum information tasks and represents an important building block for quantum technologies, with a pivotal role in the continuing progress of quantum communication, quantum computing and quantum networks. Here we review the basic theoretical ideas behind quantum teleportation and its variant protocols. We focus on the main experiments, together with the technical advantages and disadvantages associated with the use of the various technologies, from photonic qubits and optical modes to atomic ensembles, trapped atoms, and solid-state systems. Analysing the current state-of-the-art, we finish by discussing open issues, challenges and potential future implementations.
U. Alvarez-Rodriguez; M. Sanz; L. Lamata; E. Solano
2015-05-29
Quantum information provides fundamentally different computational resources than classical information. We prove that there is no unitary protocol able to add unknown quantum states belonging to different Hilbert spaces. This is an inherent restriction of quantum physics that is related to the impossibility of copying an arbitrary quantum state, i.e., the no-cloning theorem. Moreover, we demonstrate that a quantum adder, in absence of an ancillary system, is also forbidden for a known orthonormal basis. This allows us to propose an approximate quantum adder that could be implemented in the lab. Finally, we discuss the distinct character of the forbidden quantum adder for quantum states and the allowed quantum adder for density matrices.
Entanglement in systems of oscillators and quantum computations
Yuri I. Ozhigov
2012-09-03
It is shown that quantum devices based only on oscillators cannot serve as the universal quantum computer, despite of entanglement in such devices, which we roughly estimate for the ideal case and for the harmful entanglement with photonic modes. We show that quasi-particles are the native shell for the entanglement already for ground state, in contast to the free electromagnetic field where vacuum state does not produce entanglement at all.
Systematic quantum corrections to screening in thermonuclear fusion
Chitanvis, S M
2006-01-01
We develop a series expansion of the plasma screening length away from the classical limit in powers of $\\hbar^{2}$. It is shown that the leading order quantum correction increases the screening length in solar conditions by approximately 2% while it decreases the fusion rate by approximately $ 0.34%$. We also calculate the next higher order quantum correction which turns out to be approximately 0.05%.
Systematic quantum corrections to screening in thermonuclear fusion
Shirish M. Chitanvis
2006-06-13
We develop a series expansion of the plasma screening length away from the classical limit in powers of $\\hbar^{2}$. It is shown that the leading order quantum correction increases the screening length in solar conditions by approximately 2% while it decreases the fusion rate by approximately $ 0.34%$. We also calculate the next higher order quantum correction which turns out to be approximately 0.05%.
Quantum Techniques for Reaction Networks
John C. Baez
2013-06-14
Reaction networks are a general formalism for describing collections of classical entities interacting in a random way. While reaction networks are mainly studied by chemists, they are equivalent to Petri nets, which are used for similar purposes in computer science and biology. As noted by Doi and others, techniques from quantum field theory can be adapted to apply to such systems. Here we use these techniques to study how the "master equation" describing stochastic time evolution for a reaction network reduces is related to the "rate equation" describing the deterministic evolution of the expected number of particles of each species in the large-number limit. We show that the relation is especially strong when a solution of master equation is a "coherent state", meaning that the numbers of entities of each kind are described by independent Poisson distributions.
Quantum Gates for Superconducting A Dissertation
Devoret, Michel H.
, and the minimal number of non-linear circuit elements are particularly interesting, as they would reduce from Fourier analysis of the circuit Hamiltonian in a partic- ular multiply-rotating reference frame with the electromagnetic modes of an engineered quantum circuit. Doing so requires the subtle application of control
Book Review Statistical Structure of Quantum Theory
Fuchs, Christopher A.
associated with measurement processes, including measurements with a continuous number of outcomes and commutation relations, tensor products, no-go theorems for hidden variables, and symmetry operations and a detailed exposition of quantum dynamical semigroups. Chapters 4 and 5, "Repeated and Continuous Measurement
Quantum reading under a local energy constraint
Gaetana Spedalieri; Cosmo Lupo; Stefano Mancini; Samuel L. Braunstein; Stefano Pirandola
2015-09-03
Nonclassical states of light play a central role in many quantum information protocols. Their quantum features have been exploited to improve the readout of information from digital memories, modelled as arrays of microscopic beam splitters [S. Pirandola, Phys. Rev. Lett. 106, 090504 (2011)]. In this model of quantum reading, a nonclassical source of light with Einstein-Podolski-Rosen correlations has been proven to retrieve more information than any classical source. In particular, the quantum-classical comparison has been performed under a global energy constraint, i.e., by fixing the mean total number of photons irradiated over each memory cell. In this paper we provide an alternative analysis which is based on a local energy constraint, meaning that we fix the mean number of photons per signal mode irradiated over the memory cell. Under this assumption, we investigate the critical number of signal modes after which a nonclassical source of light is able to beat any classical source irradiating the same number of signals.
Nucleon semimagic numbers and low-energy neutron scattering
D. A. Zaikin; I. V. Surkova
2010-04-09
It is shown that experimental values of the cross sections of inelastic low-energy neutron scattering on even-even nuclei together with the description of these cross sections in the framework of the coupled channel optical model may be considered as a reliable method for finding nuclei with a semimagic number (or numbers) of nucleons. Some examples of the application of this method are considered.
Picture Invariance in Quantum Optics
W. -Y. Hwang
2008-08-12
We clarify the controversy over the coherent-state (CS) versus the number-state (NS) pictures in quantum optics. The NS picture is equivalent to the CS picture, as long as the phases $\\phi$ in the laser fields are randomly distributed, as M{\\o}lmer argues [\\pra {\\bf 55}, 3195 (1997)]. However, the claim by Rudolph and Sanders [Phys. Rev. Lett. {\\bf 87}, 077903 (2001)] has a few gaps. First, they make an assumption that is not necessarily true in the calculation of a density operator involved with a two-mode squeezed state. We show that there exists entanglement in the density operator without defying the assumption that phases are randomly distributed. Moreover, using a concept of picture-invariance, we argue that it is not that criteria for quantum teleportation are not satisfied. We discuss an analogy between the controversy on the CS versus NS pictures to that on the heliocentric versus geocentric pictures.
Quantum Evolution and Anticipation
Hans-Rudolf Thomann
2010-03-04
In a previous paper we have investigated quantum states evolving into mutually orthogonal states at equidistant times, and the quantum anticipation effect exhibited by measurements at one half step. Here we extend our analyzes of quantum anticipation to general type quantum evolutions and spectral measures and prove that quantum evolutions possessing an embedded orthogonal evolution are characterized by positive joint spectral measure. Furthermore, we categorize quantum evolution, assess anticipation strength and provide a framework of analytic tools and results, thus preparing for further investigation and experimental verification of anticipation in concrete physical situations such as the H-atom, which we have found to exhibit anticipation.
Quantum Storage of a Photonic Polarization Qubit in a Solid
Mustafa Gündo?an; Patrick M. Ledingham; Attaallah Almasi; Matteo Cristiani; Hugues de Riedmatten
2012-01-20
We report on the quantum storage and retrieval of photonic polarization quantum bits onto and out of a solid state storage device. The qubits are implemented with weak coherent states at the single photon level, and are stored for 500 ns in a praseodymium doped crystal with a storage and retrieval efficiency of 10%, using the atomic frequency comb scheme. We characterize the storage by using quantum state tomography, and find that the average conditional fidelity of the retrieved qubits exceeds 95% for a mean photon number mu=0.4. This is significantly higher than a classical benchmark, taking into account the Poissonian statistics and finite memory efficiency, which proves that our device functions as a quantum storage device for polarization qubits, even if tested with weak coherent states. These results extend the storage capabilities of solid state quantum memories to polarization encoding, which is widely used in quantum information science.
Strategy for quantum algorithm design assisted by machine learning
Jeongho Bang; Junghee Ryu; Seokwon Yoo; Marcin Pawlowski; Jinhyoung Lee
2014-07-17
We propose a method for quantum algorithm design assisted by machine learning. The method uses a quantum-classical hybrid simulator, where a "quantum student" is being taught by a "classical teacher." In other words, in our method, the learning system is supposed to evolve into a quantum algorithm for a given problem assisted by classical main-feedback system. Our method is applicable to design quantum oracle-based algorithm. As a case study, we chose an oracle decision problem, called a Deutsch-Jozsa problem. We showed by using Monte-Carlo simulations that our simulator can faithfully learn quantum algorithm to solve the problem for given oracle. Remarkably, learning time is proportional to the square root of the total number of parameters instead of the exponential dependance found in the classical machine learning based method.
Quasiprobability distributions in open quantum systems: spin-qubit systems
Kishore Thapliyal; Subhashish Banerjee; Anirban Pathak; S. Omkar; V. Ravishankar
2015-04-08
Quasiprobability distributions (QDs) in open quantum systems are investigated for $SU(2)$, spin like systems, having relevance to quantum optics and information. In this work, effect of both quantum non-demolition (QND) and dissipative open quantum systems, on the evolution of a number of spin QDs are investigated. Specifically, compact analytic expressions for the $W$, $P$, $Q$, and $F$ functions are obtained for some interesting single, two and three qubit states, undergoing general open system evolutions. Further, corresponding QDs are reported for an N qubit Dicke model and a spin-1 system. The existence of nonclassical characteristics are observed in all the systems investigated here. The study leads to a clear understanding of quantum to classical transition in a host of realistic physical scenarios. Variation of the amount of nonclassicality observed in the quantum systems, studied here,are also investigated using nonclassical volume.
Interferometric Tests of Planckian Quantum Geometry Models
Ohkyung Kwon; Craig J. Hogan
2015-10-01
The effect of Planck scale quantum geometrical effects on measurements with interferometers is estimated with standard physics, and with a variety of proposed extensions. It is shown that effects are negligible in standard field theory with canonically quantized gravity. Statistical noise levels are estimated in a variety of proposals for non-standard metric fluctuations, and these alternatives are constrained using upper bounds on stochastic metric fluctuations from LIGO. Idealized models of several interferometer system architectures are used to predict signal noise spectra in a quantum geometry that cannot be described by a fluctuating metric, in which position noise arises from holographic bounds on directional information. Predictions in this case are shown to be close to current and projected experimental bounds.
Interferometric Probes of Planckian Quantum Geometry
Ohkyung Kwon; Craig J. Hogan
2015-02-24
The effect of Planck scale quantum geometrical effects on measurements with interferometers is estimated with standard physics, and with a variety of proposed extensions. It is shown that effects are negligible in standard field theory with canonically quantized gravity. Statistical noise levels are estimated in a variety of proposals for non-standard metric fluctuations, and these alternatives are constrained using upper bounds on stochastic metric fluctuations from LIGO. Idealized models of several interferometer system architectures are used to predict signal noise spectra in a quantum geometry that cannot be described by a fluctuating metric, in which position noise arises from holographic bounds on directional information. Predictions in this case are shown to be close to current and projected experimental bounds.
From Quantum Information to Gravitation (in German)
Thomas Görnitz
2009-04-11
To unite quantum theory and general relativity, in a new access it is shown that from a theory of an abstract quantum information - called Protyposis - the theory of general relativity can be deduced by means of few and physically good founded reasons. "Abstract" quantum information means that primarily no special meaning is connected with it. The resulting cosmology has an isotropic and homogeneous metric and solves the so-called cosmological problems. For the Protyposis it follows an equation of states for energy density and pressure that fulfils all the energy conditions and that also gives an explanation for the dark energy. If it is demanded that the relations between spacetime structure and the material contend also hold for deviations from this ideal cosmology than General relativity results as a description for local inhomogenities.
Commensurate Two-Quantum Coherences Induced by Time-Delayed THz Fields
Fleischer, Sharly
The interaction of carbonyl sulfide dipolar gas molecules with two time-delayed, single-cycle THz pulses is shown both experimentally and theoretically to induce two-quantum rotational coherences that are significantly ...
QUANTUM DOTS Elliott H. Lieb \\Lambda and Jan Philip Solovej \\Lambda\\Lambda
QUANTUM DOTS Elliott H. Lieb \\Lambda and Jan Philip Solovej \\Lambda\\Lambda Department shown that a ThomasFermi type theory for the ground state is asymptotically correct when N and B tend
Error-suppression by energy-gap protection for quantum computation in open systems
Zhou, Xiang-Yu (Xiang-Yu Leo)
2014-01-01
Adiabatic Quantum Computation, while attractive due to its "hands-off" approach and intrinsic tolerance of noise, has not been shown to be fully fault-tolerant in a satisfying manner. The protection of the evolution from ...
Reconstructing the profile of time-varying magnetic fields with quantum sensors
Magesan, Easwar
Quantum systems have shown great promise for precision metrology thanks to advances in their control. This has allowed not only the sensitive estimation of external parameters but also the reconstruction of their temporal ...
Robert Carroll
2007-11-05
We show some relations between Ricci flow and quantum theory via Fisher information and the quantum potential.
Investigating puzzling aspects of the quantum theory by means of its hydrodynamic formulation
Sanz, A S
2015-01-01
Bohmian mechanics, a hydrodynamic formulation of the quantum theory, constitutes a useful resource to analyze the role of the phase as the mechanism responsible for the dynamical evolution of quantum systems. Here this role is discussed in the context of quantum interference. Specifically, it is shown that when dealing with two wave-packet coherent superpositions this phenomenon is analogous to an effective collision of a single wave packet with a barrier. This effect is illustrated by means of a numerical simulation of Young's two-slit experiment. Furthermore, outcomes from this analysis are also applied to a realistic simulation of Wheeler's delayed choice experiment. As it is shown, in both cases the Bohmian formulation helps to understand in a natural way (and, therefore, to demystify) what are typically regarded as paradoxical aspects of the quantum theory, simply stressing the important dynamical role played by the quantum phase. Accordingly, our conception of quantum systems should not rely on artifici...
Statistical analysis of sampling methods in quantum tomography
Thomas Kiesel
2012-06-07
In quantum physics, all measured observables are subject to statistical uncertainties, which arise from the quantum nature as well as the experimental technique. We consider the statistical uncertainty of the so-called sampling method, in which one estimates the expectation value of a given observable by empirical means of suitable pattern functions. We show that if the observable can be written as a function of a single directly measurable operator, the variance of the estimate from the sampling method equals to the quantum mechanical one. In this sense, we say that the estimate is on the quantum mechanical level of uncertainty. In contrast, if the observable depends on non-commuting operators, e.g. different quadratures, the quantum mechanical level of uncertainty is not achieved. The impact of the results on quantum tomography is discussed, and different approaches to quantum tomographic measurements are compared. It is shown explicitly for the estimation of quasiprobabilities of a quantum state, that balanced homodyne tomography does not operate on the quantum mechanical level of uncertainty, while the unbalanced homodyne detection does.
Impossibility of secure cloud quantum computing for classical client
Tomoyuki Morimae; Takeshi Koshiba
2014-07-07
The first generation quantum computer will be implemented in the cloud style, since only few groups will be able to access such an expensive and high-maintenance machine. How the privacy of the client can be protected in such a cloud quantum computing? It was theoretically shown [A. Broadbent, J. F. Fitzsimons, and E. Kashefi, Proceedings of the 50th Annual IEEE Symposium on Foundation of Computer Science, 517 (2009)], and experimentally demonstrated [S. Barz, E. Kashefi, A. Broadbent, J. F. Fitzsimons, A. Zeilinger, and P. Walther, Science {\\bf335}, 303 (2012)] that a client who can generate randomly-rotated single qubit states can delegate her quantum computing to a remote quantum server without leaking any privacy. The generation of a single qubit state is not too much burden for the client, and therefore we can say that "almost classical client" can enjoy the secure cloud quantum computing. However, isn't is possible to realize a secure cloud quantum computing for a client who is completely free from any quantum technology? Here we show that perfectly-secure cloud quantum computing is impossible for a completely classical client unless classical computing can simulate quantum computing, or a breakthrough is brought in classical cryptography.
system. Our experiment consists of ultracold sodium atoms in an accelerated standing wave of light which measurement-induced suppression of the dy- namics of a two-state driven system has been observed [15 of the Quantum Zeno and Anti-Zeno Effects in an Unstable System M. C. Fischer, B. Gutiérrez-Medina, and M
Quantum chaos and sensitivity to system parameters
Bhanot, G.V. (Institute for Advanced Study, Princeton, NJ (United States)); Parikh, J.C.; Sheorey, V.B. (Physical Research Lab., Navrangpura (India)); Pandey, A. (Jawaharlal Nehru Univ., New Delhi (India) Univ. of Rochester, NY (United States))
1990-01-01
The authors study the eigenfunctions and eigenvalues of the Hamiltonian H=p[sup 2][sub x]+p[sup 2][sub y]+x[sup 4]+y[sup 4]+[alpha]x[sup 2]y[sup 2] in the classically chaotic regime. It is shown that the overlap of wavefunctions at neighboring [alpha] values provides a sensitive measure to demonstrate the onset of chaos in quantum systems.
Fault Models for Quantum Mechanical Switching Networks
Jacob Biamonte; Jeff S. Allen; Marek A. Perkowski
2010-01-19
The difference between faults and errors is that, unlike faults, errors can be corrected using control codes. In classical test and verification one develops a test set separating a correct circuit from a circuit containing any considered fault. Classical faults are modelled at the logical level by fault models that act on classical states. The stuck fault model, thought of as a lead connected to a power rail or to a ground, is most typically considered. A classical test set complete for the stuck fault model propagates both binary basis states, 0 and 1, through all nodes in a network and is known to detect many physical faults. A classical test set complete for the stuck fault model allows all circuit nodes to be completely tested and verifies the function of many gates. It is natural to ask if one may adapt any of the known classical methods to test quantum circuits. Of course, classical fault models do not capture all the logical failures found in quantum circuits. The first obstacle faced when using methods from classical test is developing a set of realistic quantum-logical fault models. Developing fault models to abstract the test problem away from the device level motivated our study. Several results are established. First, we describe typical modes of failure present in the physical design of quantum circuits. From this we develop fault models for quantum binary circuits that enable testing at the logical level. The application of these fault models is shown by adapting the classical test set generation technique known as constructing a fault table to generate quantum test sets. A test set developed using this method is shown to detect each of the considered faults.
The Distribution of Ramsey Numbers
Lane Clark; Frank Gaitan
2014-11-10
We prove that the number of integers in the interval [0,x] that are non-trivial Ramsey numbers r(k,n) (3 <= k <= n) has order of magnitude (x ln x)**(1/2).
Blueprint for a microwave ion trap quantum computer
B. Lekitsch; S. Weidt; A. G. Fowler; K. Mølmer; S. J. Devitt; C. Wunderlich; W. K. Hensinger
2015-08-10
A universal quantum computer will have fundamental impact on a vast number of research fields and technologies. Therefore an increasingly large scientific and industrial community is working towards the realization of such a device. A large scale quantum computer is best constructed using a modular approach. We present the blueprint for an ion trap based scalable quantum computer module which makes it possible to create an arbitrarily large quantum computer architecture powered by long-wavelength radiation. This quantum computer module controls all operations as a stand-alone unit, is constructed using silicon microfabrication techniques and within reach of current technology. To perform the required quantum computations, the module makes use of long-wavelength-radiation quantum gate technology and relies only on a vacuum environment and global laser and microwave fields. To scale this microwave quantum computer architecture beyond one module we also present a new approach that makes use of ion transport between different modules, thereby allowing connections between arbitrarily many modules for a large scale architecture. A high-error-threshold surface error correction code making use of such module interactions can be implemented in the proposed architecture to execute fault-tolerant quantum logic operations. With only minor adjustments these modules are also suitable for alternative ion trap quantum computer architectures, such as schemes using photonic interconnects.
Ordered Ramsey numbers David Conlon
Fox, Jacob
Ordered Ramsey numbers David Conlon Jacob Fox Choongbum Lee Benny SudakovÂ§ Abstract Given a labeled graph H with vertex set {1, 2, . . . , n}, the ordered Ramsey number r with vertices appearing in the same order as in H. The ordered Ramsey number of a labeled graph H is at least
Hypergraph Ramsey numbers David Conlon
Fox, Jacob
Hypergraph Ramsey numbers David Conlon Jacob Fox Benny Sudakov Abstract The Ramsey number rk(s, n). In this paper we obtain new estimates for several basic hypergraph Ramsey problems. We give a new upper bound-color Ramsey number r3(n, n, n), which is the minimum N such that every 3-coloring of the triples
Data Compression with Prime Numbers
Gordon Chalmers
2005-11-16
A compression algorithm is presented that uses the set of prime numbers. Sequences of numbers are correlated with the prime numbers, and labeled with the integers. The algorithm can be iterated on data sets, generating factors of doubles on the compression.
Reconfigurable quantum metamaterials
James Q. Quach; Chun-Hsu Su; Andrew M. Martin; Andrew D. Greentree; Lloyd C. L. Hollenberg
2011-06-04
By coupling controllable quantum systems into larger structures we introduce the concept of a quantum metamaterial. Conventional meta-materials represent one of the most important frontiers in optical design, with applications in diverse fields ranging from medicine to aerospace. Up until now however, metamaterials have themselves been classical structures and interact only with the classical properties of light. Here we describe a class of dynamic metamaterials, based on the quantum properties of coupled atom-cavity arrays, which are intrinsically lossless, reconfigurable, and operate fundamentally at the quantum level. We show how this new class of metamaterial could be used to create a reconfigurable quantum superlens possessing a negative index gradient for single photon imaging. With the inherent features of quantum superposition and entanglement of metamaterial properties, this new class of dynamic quantum metamaterial, opens a new vista for quantum science and technology.
Quantum convolutional stabilizer codes
Chinthamani, Neelima
2004-09-30
Quantum error correction codes were introduced as a means to protect quantum information from decoherance and operational errors. Based on their approach to error control, error correcting codes can be divided into two different classes: block codes...
Integral Modular Categories and Integrality of Quantum Invariants at Roots of Unity of
Masbaum, Gregor
Integral Modular Categories and Integrality of Quantum Invariants at Roots of Unity of Prime Order G. Masbaum H. Wenzl May 29, 1998 \\Lambda Abstract It is shown how to deduce integrality properties of quantum 3manifold invari ants from the existence of integral subcategories of modular categories
Acceleration of positrons by a relativistic electron beam in the presence of quantum effects
Niknam, A. R.; Aki, H.; Khorashadizadeh, S. M.
2013-09-15
Using the quantum magnetohydrodynamic model and obtaining the dispersion relation of the Cherenkov and cyclotron waves, the acceleration of positrons by a relativistic electron beam is investigated. The Cherenkov and cyclotron acceleration mechanisms of positrons are compared together. It is shown that growth rate and, therefore, the acceleration of positrons can be increased in the presence of quantum effects.
Quantum optics with single nanodiamonds flying over gold films: Towards a Robust quantum plasmonics
Mollet, O.; Drezet, A.; Huant, S.
2013-12-04
A nanodiamond (ND) hosting nitrogen-vacancy (NV) color centers is attached on the apex of an optical tip for near-field microscopy. Its fluorescence is used to launch surface plasmon-polaritons (SPPs) in a thin polycrystalline gold film. It is shown that the quantum nature of the initial source of light is preserved after conversion to SPPs. This opens the way to a deterministic quantum plasmonics, where single SPPs can be injected at well-defined positions in a plasmonic device produced by top-down approaches.
Quantum Optics With Single Nanodiamonds Flying Over Gold Films: Towards A Robust Quantum Plasmonics
Mollet, O; Huant, S
2013-01-01
A nanodiamond (ND) hosting nitrogen-vacancy (NV) color centers is attached on the apex of an optical tip for near-field microscopy. Its fluorescence is used to launch surface plasmon-polaritons (SPPs) in a thin polycrystalline gold film. It is shown that the quantum nature of the initial source of light is preserved after conversion to SPPs. This opens the way to a deterministic quantum plasmonics, where single SPPs can be injected at well-defined positions in a plasmonic device produced by top-down approaches.
Jae-Suk Park; John Terilla; Thomas Tradler
2009-09-21
We introduce the concept of a quantum background and a functor QFT. In the case that the QFT moduli space is smooth formal, we construct a flat quantum superconnection on a bundle over QFT which defines algebraic structures relevant to correlation functions in quantum field theory. We go further and identify chain level generalizations of correlation functions which should be present in all quantum field theories.
Amit Dutta; Gabriel Aeppli; Bikas K. Chakrabarti; Uma Divakaran; Thomas F. Rosenbaum; Diptiman Sen
2015-06-09
We review quantum phase transitions of spin systems in transverse magnetic fields taking the examples of the spin-1/2 Ising and XY models in a transverse field. Beginning with an overview of quantum phase transitions, we introduce a number of model Hamiltonians. We provide exact solutions in one spatial dimension connecting them to conformal field theoretical studies. We also discuss Kitaev models and some other exactly solvable spin systems. Studies of quantum phase transitions in the presence of quenched randomness and with frustrating interactions are presented in detail. We discuss novel phenomena like Griffiths-McCoy singularities. We then turn to more recent topics like information theoretic measures of the quantum phase transitions in these models such as concurrence, entanglement entropy, quantum discord and quantum fidelity. We then focus on non-equilibrium dynamics of a variety of transverse field systems across quantum critical points and lines. After mentioning rapid quenching studies, we dwell on slow dynamics and discuss the Kibble-Zurek scaling for the defect density following a quench across critical points and its modifications for quenching across critical lines, gapless regions and multicritical points. Topics like the role of different quenching schemes, local quenching, quenching of models with random interactions and quenching of a spin chain coupled to a heat bath are touched upon. The connection between non-equilibrium dynamics and quantum information theoretic measures is presented at some length. We indicate the connection between Kibble-Zurek scaling and adiabatic evolution of a state as well as the application of adiabatic dynamics as a tool of a quantum optimization technique known as quantum annealing. The final section is dedicated to a detailed discussion on recent experimental studies of transverse Ising-like systems.
1999 Macmillan Magazines Ltd which is proportional to the number of pho-
Newsome, William
. In the latter case, the net energy exchange is zero, but it can be shown that because of this `Rabi cycle trick is used: the interaction is fully resonant and thus much larger. An energy exchange does occur the cavity is initially in an arbitrary quantum superposition, or mixture, of zero-photon and one
Stephen Hawking Quantum Gravity
Visser, Matt
Stephen Hawking and Quantum Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 4 Nov 2000 #12; Stephen Hawking and Quantum Gravity Abstract: Through research, Stephen Hawking has captured a place in the popular imagina- tion. Quantum gravity in its various
Giulio Chiribella; Giacomo Mauro D'Ariano; Paolo Perinotti
2007-12-09
We present a method for optimizing quantum circuits architecture. The method is based on the notion of "quantum comb", which describes a circuit board in which one can insert variable subcircuits. The method allows one to efficiently address novel kinds of quantum information processing tasks, such as storing-retrieving, and cloning of channels.
Matthew James
2014-06-20
This paper explains some fundamental ideas of {\\em feedback} control of quantum systems through the study of a relatively simple two-level system coupled to optical field channels. The model for this system includes both continuous and impulsive dynamics. Topics covered in this paper include open and closed loop control, impulsive control, optimal control, quantum filtering, quantum feedback networks, and coherent feedback control.
Introduction to Quantum Mechanics
Eduardo J. S. Villaseñor
2008-04-23
The purpose of this contribution is to give a very brief introduction to Quantum Mechanics for an audience of mathematicians. I will follow Segal's approach to Quantum Mechanics paying special attention to algebraic issues. The usual representation of Quantum Mechanics on Hilbert spaces is also discussed.
Randall Espinoza; Tom Imbo; Paul Lopata
2004-03-30
We investigate an entangled deformation of the deterministic quantum cloning process, called enscription, that can be applied to (certain) sets of distinct quantum states which are not necessarily orthogonal, called texts. Some basic theorems on enscribable texts are given, and a relationship to probabilistic quantum cloning is demonstrated.
Vacuum energy: quantum hydrodynamics vs quantum gravity
G. E. Volovik
2005-09-09
We compare quantum hydrodynamics and quantum gravity. They share many common features. In particular, both have quadratic divergences, and both lead to the problem of the vacuum energy, which in the quantum gravity transforms to the cosmological constant problem. We show that in quantum liquids the vacuum energy density is not determined by the quantum zero-point energy of the phonon modes. The energy density of the vacuum is much smaller and is determined by the classical macroscopic parameters of the liquid including the radius of the liquid droplet. In the same manner the cosmological constant is not determined by the zero-point energy of quantum fields. It is much smaller and is determined by the classical macroscopic parameters of the Universe dynamics: the Hubble radius, the Newton constant and the energy density of matter. The same may hold for the Higgs mass problem: the quadratically divergent quantum correction to the Higgs potential mass term is also cancelled by the microscopic (trans-Planckian) degrees of freedom due to thermodynamic stability of the whole quantum vacuum.
Quantum chaos in quantum Turing machines
Ilki Kim; Guenter Mahler
1999-10-18
We investigate a 2-spin quantum Turing architecture, in which discrete local rotations \\alpha_m of the Turing head spin alternate with quantum controlled NOT-operations. We demonstrate that a single chaotic parameter input \\alpha_m leads to a chaotic dynamics in the entire Hilbert-space.
Quantum attacks against iterated block ciphers
Marc Kaplan
2015-04-26
We study the amplification of security against quantum attacks provided by iteration of block ciphers. In the classical case, the Meet-in-the-middle attack is a generic attack against those constructions. This attack reduces the time required to break double iterations to only twice the time it takes to attack a single block cipher, given that the attacker has access to a large amount of memory. More abstractly, it shows that security by composition does not achieve exact multiplicative amplification. We present a quantized version of this attack based on an optimal quantum algorithm for the Element Distinctness problem. We then use the generalized adversary method to prove the optimality of the attack. An interesting corollary is that the time-space tradeoff for quantum attacks is very different from what classical attacks allow. This first result seems to indicate that composition resists better to quantum attacks than to classical ones because it prevents the quadratic speedup achieved by quantizing an exhaustive search. We investigate security amplification by composition further by examining the case of four iterations. We quantize a recent technique called the dissection attack using the framework of quantum walks. Surprisingly, this leads to better gains over classical attacks than for double iterations, which seems to indicate that when the number of iterations grows, the resistance against quantum attacks decreases.
Quantum model of microcavity intersubband electroluminescent devices
Simone De Liberato; Cristiano Ciuti
2008-04-28
We present a quantum theoretical analysis of the electroluminescence from an intersubband transition of a quantum well structure embedded in a planar microcavity. By using a cluster factorization method, we have derived a closed set of dynamical equations for the quantum well carrier and cavity photon occupation numbers, the correlation between the cavity field and the intersubband polarization, as well as polarization-polarization contributions. In order to model the electrical excitation, we have considered electron population tunneling from an injector and into an extractor contact. The tunneling rates have been obtained by considering the bare electronic states in the quantum well and the limit of validity of this approximation (broad-band injection) are discussed in detail. We apply the present quantum model to provide a comprehensive description of the electronic transport and optical properties of an intersubband microcavity light emitting diode, accounting for non-radiative carrier relaxation and Pauli blocking. We study the enhancement of the electroluminescence quantum efficiency passing from the weak to the strong polariton coupling regime.
Classical and Quantum Mechanics via Lie algebras
Arnold Neumaier; Dennis Westra
2011-04-14
The goal of this book is to present classical mechanics, quantum mechanics, and statistical mechanics in an almost completely algebraic setting, thereby introducing mathematicians, physicists, and engineers to the ideas relating classical and quantum mechanics with Lie algebras and Lie groups. The book emphasizes the closeness of classical and quantum mechanics, and the material is selected in a way to make this closeness as apparent as possible. Much of the material covered here is not part of standard textbook treatments of classical or quantum mechanics (or is only superficially treated there). For physics students who want to get a broader view of the subject, this book may therefore serve as a useful complement to standard treatments of quantum mechanics. Almost without exception, this book is about precise concepts and exact results in classical mechanics, quantum mechanics, and statistical mechanics. The structural properties of mechanics are discussed independent of computational techniques for obtaining quantitatively correct numbers from the assumptions made. The standard approximation machinery for calculating from first principles explicit thermodynamic properties of materials, or explicit cross sections for high energy experiments can be found in many textbooks and is not repeated here.
Fourier Transform Quantum State Tomography
Mohammadreza Mohammadi; Agata M. Branczyk; Daniel F. V. James
2013-01-17
We propose a technique for performing quantum state tomography of photonic polarization-encoded multi-qubit states. Our method uses a single rotating wave plate, a polarizing beam splitter and two photon-counting detectors per photon mode. As the wave plate rotates, the photon counters measure a pseudo-continuous signal which is then Fourier transformed. The density matrix of the state is reconstructed using the relationship between the Fourier coefficients of the signal and the Stokes' parameters that represent the state. The experimental complexity, i.e. different wave plate rotation frequencies, scales linearly with the number of qubits.
Thermodynamics of discrete quantum processes
Janet Anders; Vittorio Giovannetti
2012-11-01
We define thermodynamic configurations and identify two primitives of discrete quantum processes between configurations for which heat and work can be defined in a natural way. This allows us to uncover a general second law for any discrete trajectory that consists of a sequence of these primitives, linking both equilibrium and non-equilibrium configurations. Moreover, in the limit of a discrete trajectory that passes through an infinite number of configurations, i.e. in the reversible limit, we recover the saturation of the second law. Finally, we show that for a discrete Carnot cycle operating between four configurations one recovers Carnot's thermal efficiency.
Quantum Information Science | ornl.gov
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Engineering Analysis Behavioral Sciences Geographic Information Science and Technology Quantum Information Science Quantum Communication and Security Quantum-Enhanced Sensing...
Single-photon Resolved Cross-Kerr Interaction for Autonomous Stabilization of Photon-number States
E. T. Holland; B. Vlastakis; R. W. Heeres; M. J. Reagor; U. Vool; Z. Leghtas; L. Frunzio; G. Kirchmair; M. H. Devoret; M. Mirrahimi; R. J. Schoelkopf
2015-04-13
Quantum states can be stabilized in the presence of intrinsic and environmental losses by either applying active feedback conditioned on an ancillary system or through reservoir engineering. Reservoir engineering maintains a desired quantum state through a combination of drives and designed entropy evacuation. We propose and implement a quantum reservoir engineering protocol that stabilizes Fock states in a microwave cavity. This protocol is realized with a circuit quantum electrodynamics platform where a Josephson junction provides direct, nonlinear coupling between two superconducting waveguide cavities. The nonlinear coupling results in a single photon resolved cross-Kerr effect between the two cavities enabling a photon number dependent coupling to a lossy environment. The quantum state of the microwave cavity is discussed in terms of a net polarization and is analyzed by a measurement of its steady state Wigner function.
Trading classical and quantum computational resources
Sergey Bravyi; Graeme Smith; John Smolin
2015-06-03
We propose examples of a hybrid quantum-classical simulation where a classical computer assisted by a small quantum processor can efficiently simulate a larger quantum system. First we consider sparse quantum circuits such that each qubit participates in O(1) two-qubit gates. It is shown that any sparse circuit on n+k qubits can be simulated by sparse circuits on n qubits and a classical processing that takes time $2^{O(k)} poly(n)$. Secondly, we study Pauli-based computation (PBC) where allowed operations are non-destructive eigenvalue measurements of n-qubit Pauli operators. The computation begins by initializing each qubit in the so-called magic state. This model is known to be equivalent to the universal quantum computer. We show that any PBC on n+k qubits can be simulated by PBCs on n qubits and a classical processing that takes time $2^{O(k)} poly(n)$. Finally, we propose a purely classical algorithm that can simulate a PBC on n qubits in a time $2^{c n} poly(n)$ where $c\\approx 0.94$. This improves upon the brute-force simulation method which takes time $2^n poly(n)$. Our algorithm exploits the fact that n-fold tensor products of magic states admit a low-rank decomposition into n-qubit stabilizer states.
Pierre-Luc Dallaire-Demers; Frank K. Wilhelm
2015-08-18
Many phenomena of strongly correlated materials are encapsulated in the Fermi-Hubbard model whose thermodynamical properties can be computed from its grand canonical potential according to standard procedures. In general, there is no closed form solution for lattices of more than one spatial dimension, but solutions can be approximated with cluster perturbation theory. To model long-range effects such as order parameters, a powerful method to compute the cluster's Green's function consists in finding its self-energy through a variational principle of the grand canonical potential. This opens the possibility of studying various phase transitions at finite temperature in the Fermi-Hubbard model. However, a classical cluster solver quickly hits an exponential wall in the memory (or computation time) required to store the computation variables. Here it is shown theoretically that that the cluster solver can be mapped to a subroutine on a quantum computer whose quantum memory scales as the number of orbitals in the simulated cluster. A quantum computer with a few tens of qubits could therefore simulate the thermodynamical properties of complex fermionic lattices inaccessible to classical supercomputers.
Pierre-Luc Dallaire-Demers; Frank K. Wilhelm
2015-11-27
Many phenomena of strongly correlated materials are encapsulated in the Fermi-Hubbard model whose thermodynamical properties can be computed from its grand canonical potential according to standard procedures. In general, there is no closed form solution for lattices of more than one spatial dimension, but solutions can be approximated with cluster perturbation theory. To model long-range effects such as order parameters, a powerful method to compute the cluster's Green's function consists in finding its self-energy through a variational principle of the grand canonical potential. This opens the possibility of studying various phase transitions at finite temperature in the Fermi-Hubbard model. However, a classical cluster solver quickly hits an exponential wall in the memory (or computation time) required to store the computation variables. Here it is shown theoretically that that the cluster solver can be mapped to a subroutine on a quantum computer whose quantum memory scales as the number of orbitals in the simulated cluster. A quantum computer with a few tens of qubits could therefore simulate the thermodynamical properties of complex fermionic lattices inaccessible to classical supercomputers.
Laser-like instabilities in quantum nano-electromechanical systems S. D. Bennett and A. A. Clerk
Bennett, Steven D.
Laser-like instabilities in quantum nano-electromechanical systems S. D. Bennett and A. A. Clerk; published 9 November 2006 We discuss negative damping regimes in quantum nano-electromechanical systemsRevB.74.201301 PACS number s : 73.23.Hk, 85.85. j, 72.70. m At their heart, quantum nano-electromechanical
Geller, Michael R.
2013-01-01
code. Section III maps the calculation of the ground-state energy for the TIM onto a quantum phase in the transverse Ising model (TIM) [12], there is a large number of physical qubits and lengthy computational time]. Here we investigate the quantum simulation of the TIM ground-state energy on a surface code quantum
On the explanation for quantum statistics
Simon Saunders
2005-11-15
The concept of classical indistinguishability is analyzed and defended against a number of well-known criticisms, with particular attention to the Gibbs' paradox. Granted that it is as much at home in classical as in quantum statistical mechanics, the question arises as to why indistinguishability, in quantum mechanics but not in classical mechanics, forces a change in statistics. The answer, illustrated with simple examples, is that the equilibrium measure on classical phase space is continuous, whilst on Hilbert space it is discrete. The relevance of names, or equivalently, properties stable in time that can be used as names, is also discussed.
Quantum Accelerator Modes from the Farey Tree
A. Buchleitner; M. B. d'Arcy; S. Fishman; S. A. Gardiner; I. Guarneri; Z. -Y. Ma; L. Rebuzzini; G. S. Summy
2006-06-09
We show that mode-locking finds a purely quantum non-dissipative counterpart in atom-optical quantum accelerator modes. These modes are formed by exposing cold atoms to periodic kicks in the direction of the gravitational field. They are anchored to generalized Arnol'd tongues, parameter regions where driven nonlinear classical systems exhibit mode-locking. A hierarchy for the rational numbers known as the Farey Tree provides an ordering of the Arnol'd tongues and hence of experimentally observed accelerator modes.
Mario Stip?evi?; John Bowers
2014-10-09
We present a random number generator based on quantum effects in photonic emission and detection. It is unique in simultaneous use of both spatial and temporal quantum information contained in the system which makes it resilient to hardware failure and signal injection attacks. We show that its deviation from randomness cam be estimated based on simple measurements. Generated numbers pass NIST Statistical test suite without post-processing.
Properties of reactive oxygen species by quantum Monte Carlo
Zen, Andrea; Trout, Bernhardt L.; Guidoni, Leonardo
2014-07-07
The electronic properties of the oxygen molecule, in its singlet and triplet states, and of many small oxygen-containing radicals and anions have important roles in different fields of chemistry, biology, and atmospheric science. Nevertheless, the electronic structure of such species is a challenge for ab initio computational approaches because of the difficulties to correctly describe the statical and dynamical correlation effects in presence of one or more unpaired electrons. Only the highest-level quantum chemical approaches can yield reliable characterizations of their molecular properties, such as binding energies, equilibrium structures, molecular vibrations, charge distribution, and polarizabilities. In this work we use the variational Monte Carlo (VMC) and the lattice regularized Monte Carlo (LRDMC) methods to investigate the equilibrium geometries and molecular properties of oxygen and oxygen reactive species. Quantum Monte Carlo methods are used in combination with the Jastrow Antisymmetrized Geminal Power (JAGP) wave function ansatz, which has been recently shown to effectively describe the statical and dynamical correlation of different molecular systems. In particular, we have studied the oxygen molecule, the superoxide anion, the nitric oxide radical and anion, the hydroxyl and hydroperoxyl radicals and their corresponding anions, and the hydrotrioxyl radical. Overall, the methodology was able to correctly describe the geometrical and electronic properties of these systems, through compact but fully-optimised basis sets and with a computational cost which scales as N{sup 3} ? N{sup 4}, where N is the number of electrons. This work is therefore opening the way to the accurate study of the energetics and of the reactivity of large and complex oxygen species by first principles.
Quantum Physics and Nanotechnology
Vladimir K. Nevolin
2011-06-06
Experimental studies of infinite (unrestricted at least in one direction) quantum particle motion using probe nanotechnologies have revealed the necessity of revising previous concepts of their motion. Particularly, quantum particles transfer quantum motion nonlocality energy beside classical kinetic energy, in other words, they are in two different kinds of motion simultaneously. The quantum component of the motion energy may be quite considerable under certain circumstances. Some new effects were predicted and proved experimentally in terms of this phenomenon. A new prototype refrigerating device was tested, its principle of operation being based on the effect of transferring the quantum component of the motion energy.
Algorithms for Quantum Computers
Jamie Smith; Michele Mosca
2010-01-07
This paper surveys the field of quantum computer algorithms. It gives a taste of both the breadth and the depth of the known algorithms for quantum computers, focusing on some of the more recent results. It begins with a brief review of quantum Fourier transform based algorithms, followed by quantum searching and some of its early generalizations. It continues with a more in-depth description of two more recent developments: algorithms developed in the quantum walk paradigm, followed by tensor network evaluation algorithms (which include approximating the Tutte polynomial).
Scalable optical quantum computer
Manykin, E A; Mel'nichenko, E V [Institute for Superconductivity and Solid-State Physics, Russian Research Centre 'Kurchatov Institute', Moscow (Russian Federation)
2014-12-31
A way of designing a scalable optical quantum computer based on the photon echo effect is proposed. Individual rare earth ions Pr{sup 3+}, regularly located in the lattice of the orthosilicate (Y{sub 2}SiO{sub 5}) crystal, are suggested to be used as optical qubits. Operations with qubits are performed using coherent and incoherent laser pulses. The operation protocol includes both the method of measurement-based quantum computations and the technique of optical computations. Modern hybrid photon echo protocols, which provide a sufficient quantum efficiency when reading recorded states, are considered as most promising for quantum computations and communications. (quantum computer)
Raj Chakrabarti; Herschel Rabitz
2007-10-03
Numerous lines of experimental, numerical and analytical evidence indicate that it is surprisingly easy to locate optimal controls steering quantum dynamical systems to desired objectives. This has enabled the control of complex quantum systems despite the expense of solving the Schrodinger equation in simulations and the complicating effects of environmental decoherence in the laboratory. Recent work indicates that this simplicity originates in universal properties of the solution sets to quantum control problems that are fundamentally different from their classical counterparts. Here, we review studies that aim to systematically characterize these properties, enabling the classification of quantum control mechanisms and the design of globally efficient quantum control algorithms.
Discrimination of Optical Coherent States using a Photon Number Resolving Detector
Christoffer Wittmann; Ulrik L. Andersen; Gerd Leuchs
2009-07-14
The discrimination of non-orthogonal quantum states with reduced or without errors is a fundamental task in quantum measurement theory. In this work, we investigate a quantum measurement strategy capable of discriminating two coherent states probabilistically with significantly smaller error probabilities than can be obtained using non-probabilistic state discrimination. We find that appropriate postselection of the measurement data of a photon number resolving detector can be used to discriminate two coherent states with small error probability. We compare our new receiver to an optimal intermediate measurement between minimum error discrimination and unambiguous state discrimination.
Economical standard quantum process tomography
Xiaohua Wu; Ke Xu
2011-05-12
Recently, Bendersky \\emph{et al.} developed a method to complete the task of characterizing an arbitrary $\\chi$ matrix element in a scalable way, Phys. Rev. Lett. Vol. \\textbf{100}, 190403(2008), where an auxiliary system was needed. In present work, we shall show that the same task can also be completed within the scheme of standard quantum process tomography (SQPT) where there is no requirement for ancilla. Our method depends on two observations: With the elaborately chosen operators basis, the SQPT may have an economical form where a single run of experiment, in which we measure the expectation value of a chosen operator in the outport of the quantum channel with a known input, is sufficient to characterize a selected $\\chi$ matrix element; With the progress recently achieved in quantum entanglement detection, we also find that the number of the experimental settings to realize the experiment for the selected $\\chi$ matrix element does not exceed 2N for the N-qubits system. For practice, our scheme can be applied for the cases where the controlled two-body interaction is neither available nor desirable.
Quantum Foam, Gravity and Gravitational Waves
Cahill, R T
2003-01-01
The new information-theoretic Process Physics has shown that space is a quantum foam system with gravity being, in effect, an inhomogeneous in-flow of the quantum foam into matter. The theory predicts that absolute motion with respect to this system should be observable, and it is shown here that absolute motion has been detected in at least seven experiments. As well this experimental data also reveals the existence of a gravitational wave phenomena associated with the in-flow. It is shown that Galilean Relativity and Special Relativity are in fact compatible, contrary to current beliefs: absolute motion actually causes the special relativity effects. The new theory of gravity passes all the tests of the previous Newtonian and General Relativity theories, but in addition resolves the numerous gravitational anomalies such as the spiral galaxy `dark matter' effect, the absence of `dark matter' in elliptical galaxies, the inconsistencies in measuring G, the borehole g anomaly, and others. It is shown that Newto...
Quantum Discord and its Role in Quantum Information Theory
Alexander Streltsov
2014-11-12
Quantum entanglement is the most popular kind of quantum correlations, and its fundamental role in several tasks in quantum information theory like quantum cryptography, quantum dense coding, and quantum teleportation is undeniable. However, recent results suggest that various applications in quantum information theory do not require entanglement, and that their performance can be captured by a new type of quantum correlations which goes beyond entanglement. Quantum discord, introduced by Zurek more than a decade ago, is the most popular candidate for such general quantum correlations. In this work we give an introduction to this modern research direction. After a short review of the main concepts of quantum theory and entanglement, we present quantum discord and general quantum correlations, and discuss three applications which are based on this new type of correlations: remote state preparation, entanglement distribution, and transmission of correlations. We also give an outlook to other research in this direction.
Entanglement distribution over quantum code-division-multiple-access networks
Chang-long Zhu; Nan Yang; Yu-xi Liu; Franco Nori; Jing Zhang
2015-07-09
We present a method for quantum entanglement distribution over a so-called code-division-multiple-access network, in which two pairs of users share the same quantum channel to transmit information. The main idea of this method is to use different broad-band chaotic phase shifts, generated by electro-optic modulators (EOMs) and chaotic Colpitts circuits, to encode the information-bearing quantum signals coming from different users, and then recover the masked quantum signals at the receiver side by imposing opposite chaotic phase shifts. The chaotic phase shifts given to different pairs of users are almost uncorrelated due to the randomness of chaos and thus the quantum signals from different pair of users can be distinguished even when they are sent via the same quantum channel. It is shown that two maximally-entangled states can be generated between two pairs of users by our method mediated by bright coherent lights, which can be more easily implemented in experiments compared with single-photon lights. Our method is robust under the channel noises if only the decay rates of the information-bearing fields induced by the channel noises are not quite high. Our study opens up new perspectives for addressing and transmitting quantum information in future quantum networks.
Quantum Thermodynamic Cycles and Quantum Heat Engines (II)
H. T. Quan
2009-03-09
We study the quantum mechanical generalization of force or pressure, and then we extend the classical thermodynamic isobaric process to quantum mechanical systems. Based on these efforts, we are able to study the quantum version of thermodynamic cycles that consist of quantum isobaric process, such as quantum Brayton cycle and quantum Diesel cycle. We also consider the implementation of quantum Brayton cycle and quantum Diesel cycle with some model systems, such as single particle in 1D box and single-mode radiation field in a cavity. These studies lay the microscopic (quantum mechanical) foundation for Szilard-Zurek single molecule engine.
Compendium of Experimental Cetane Numbers
Yanowitz, J.; Ratcliff, M. A.; McCormick, R. L.; Taylor, J. D.; Murphy, M. J.
2014-08-01
This report is an updated version of the 2004 Compendium of Experimental Cetane Number Data and presents a compilation of measured cetane numbers for pure chemical compounds. It includes all available single compound cetane number data found in the scientific literature up until March 2014 as well as a number of unpublished values, most measured over the past decade at the National Renewable Energy Laboratory. This Compendium contains cetane values for 389 pure compounds, including 189 hydrocarbons and 201 oxygenates. More than 250 individual measurements are new to this version of the Compendium. For many compounds, numerous measurements are included, often collected by different researchers using different methods. Cetane number is a relative ranking of a fuel's autoignition characteristics for use in compression ignition engines; it is based on the amount of time between fuel injection and ignition, also known as ignition delay. The cetane number is typically measured either in a single-cylinder engine or a constant volume combustion chamber. Values in the previous Compendium derived from octane numbers have been removed, and replaced with a brief analysis of the correlation between cetane numbers and octane numbers. The discussion on the accuracy and precision of the most commonly used methods for measuring cetane has been expanded and the data has been annotated extensively to provide additional information that will help the reader judge the relative reliability of individual results.
Quantum Chaos and Quantum Computers D. L. Shepelyansky*
Shepelyansky, Dima
Quantum Chaos and Quantum Computers D. L. Shepelyansky* Laboratoire de Physique Quantique, UMR 5626 analytically and numerically and the border for emergence of quantum chaos, induced by imperfections without any external decoherence. The onset of quantum chaos leads to quantum computer hard- ware melting
Universal Single-Server Blind Quantum Computation for Classical Client
Hai-Ru Xu; Bang-Hai Wang
2014-11-12
Blind quantum computation allows a client without enough quantum technologies to delegate her quantum computation to quantum server, while keeping her input, output and algorithm secure. In this paper, we propose a universal single-server and classical-client blind quantum computation protocol based on entanglement swapping technology. In our protocol, the client interface with only one server and the only ability of the client requires is to get particles from trusted center and forward them to the server. Moreover, the protocol can be modified to make client completely classical by improving the ability of the trusted center. Numbers of blind quantum computation protocols have been presented in recent years, including single-, double- and triple-server protocols. In the single-server protocol, client needs to prepare single qubits. Though client can be classical in the double-server protocol, the two servers, who share Bell state from trusted center, are not allowed to communicate with each other. Recently, the triple-server protocol solves the noncommunication problem. Three servers, however, make the implementation of the computation sophisticated and unrealistic. Since it is impossible for blind quantum computation with only classical client and single server, blind quantum computation may work in the "Cloud + E-commerce" style in the future. Our protocol might become a key ingredient for real-life application in the first generation of quantum computations.
Direct Sum Theorem for Bounded Round Quantum Communication Complexity
Dave Touchette
2014-09-15
We prove a direct sum theorem for bounded round entanglement-assisted quantum communication complexity. To do so, we use the fully quantum definition for information cost and complexity that we recently introduced, and use both the fact that information is a lower bound on the communication, and the fact that a direct sum property holds for quantum information complexity. We then give a protocol for compressing a single copy of a protocol down to its quantum information cost, up to terms depending on the number of rounds and the allowed increase in error. Two important tools to derive this protocol are a smooth conditional min-entropy bound for a one-shot quantum state redistribution protocol, and the quantum substate theorem of Jain, Radhakrishnan and Sen (FOCS'02) to transform this bound into a von Neumann conditional entropy bound. This result further establishes the newly introduced notions of quantum information cost and complexity as the correct quantum generalisations of the classical ones in the standard communication complexity setting. Finding such a quantum generalization of information complexity was one of the open problem recently raised by Braverman (STOC'12).
Reaching a Quantum Consensus: Master Equations that Generate Symmetrization and Synchronization
Guodong Shi; Daoyi Dong; Ian R. Petersen; Karl Henrik Johansson
2015-05-05
In this paper, we propose and study a master-equation based approach to drive a quantum network with $n$ qubits to a consensus (symmetric) state introduced by Mazzarella et al. The state evolution of the quantum network is described by a Lindblad master equation with the Lindblad terms generated by continuous-time swapping operators, which also introduce an underlying interaction graph. We establish a graphical method that bridges the proposed quantum consensus scheme and classical consensus dynamics by studying an induced graph (with $2^{2n}$ nodes) of the quantum interaction graph (with $n$ qubits). A fundamental connection is then shown that quantum consensus over the quantum graph is equivalent to componentwise classical consensus over the induced graph, which allows various existing works on classical consensus to be applicable to the quantum setting. Some basic scaling and structural properties of the quantum induced graph are established via combinatorial analysis. Necessary and sufficient conditions for exponential and asymptotic quantum consensus are obtained, respectively, for switching quantum interaction graphs. As a quantum analogue of classical synchronization of coupled oscillators, quantum synchronization conditions are also presented, in which the reduced states of all qubits tend to a common trajectory.
Deformed quantum double realization of the toric code and beyond
Pramod Padmanabhan; Juan Pablo Ibieta Jimenez; Miguel Jorge Bernabé Ferreira; Paulo Teotonio-Sobrinho
2015-12-10
Quantum double models, such as the toric code, can be constructed from transfer matrices of lattice gauge theories with discrete gauge groups and parametrized by the center of the gauge group algebra and its dual. For general choices of these parameters the transfer matrix contains operators acting on links which can also be thought of as perturbations to the quantum double model driving it out of its topological phase and destroying the exact solvability of the quantum double model. We modify these transfer matrices with perturbations and extract exactly solvable models which remain in a quantum phase, thus nullifying the effect of the perturbation. The algebra of the modified vertex and plaquette operators now obey a deformed version of the quantum double algebra. The Abelian cases are shown to be in the quantum double phase whereas the non-Abelian phases are shown to be in a modified phase of the corresponding quantum double phase. These are illustrated with the groups $\\mathbb{Z}_n$ and $S_3$. The quantum phases are determined by studying the excitations of these systems namely their fusion rules and the statistics. We then go further to construct a transfer matrix which contains the other $\\mathbb{Z}_2$ phase namely the double semion phase. More generally for other discrete groups these transfer matrices contain the twisted quantum double models. These transfer matrices can be thought of as being obtained by introducing extra parameters into the transfer matrix of lattice gauge theories. These parameters are central elements belonging to the tensor products of the algebra and its dual and are associated to vertices and volumes of the three dimensional lattice. As in the case of the lattice gauge theories we construct the operators creating the excitations in this case and study their braiding and fusion properties.
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AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Homesum_a_epg0_fpd_mmcf_m.xls" ,"Available from WebQuantity of NaturalDukeWakefield Municipal Gas &SCE-SessionsSouthReport for the Weldon Spring,7=cr5rnP 7694 i+lJNew York,' , /v-i 2
Quantum cryptographic system with reduced data loss
Lo, H.K.; Chau, H.F.
1998-03-24
A secure method for distributing a random cryptographic key with reduced data loss is disclosed. Traditional quantum key distribution systems employ similar probabilities for the different communication modes and thus reject at least half of the transmitted data. The invention substantially reduces the amount of discarded data (those that are encoded and decoded in different communication modes e.g. using different operators) in quantum key distribution without compromising security by using significantly different probabilities for the different communication modes. Data is separated into various sets according to the actual operators used in the encoding and decoding process and the error rate for each set is determined individually. The invention increases the key distribution rate of the BB84 key distribution scheme proposed by Bennett and Brassard in 1984. Using the invention, the key distribution rate increases with the number of quantum signals transmitted and can be doubled asymptotically. 23 figs.
Quantum Phase Transition in a Graphene Model
Simon Hands; Costas Strouthos
2008-08-20
We present results for the equation of state of a graphene-like model in an effort to understand the properties of its quantum phase transition. The N_f fermion species interact through a three dimensional instantaneous Coulomb potential. Since there are no reliable analytical tools that work for all values of N_f and the coupling constant g, we rely on Monte Carlo simulations to calculate the critical properties of the model near the phase transition. We consider the four-component formulation for the fermion fields, which arises naturally as the continuum limit of the staggered fermion construction in (2+1) dimensions. In the limit of infinitely strong Coulomb interaction, the system undergoes a quantum phase transition at a critical number of fermion species N_fc ~ 4.7. We also calculate the values of the critical exponents at the quantum phase transition.
QAM Adaptive Measurements Feedback Quantum Receiver Performance
Tian Chen; Ke Li; Yuan Zuo; Bing Zhu
2015-04-11
We theoretically study the quantum receivers with adaptive measurements feedback for discriminating quadrature amplitude modulation (QAM) coherent states in terms of average symbol error rate. For rectangular 16-QAM signal set, with different stages of adaptive measurements, the effects of realistic imperfection parameters including the sub-unity quantum efficiency and the dark counts of on-off detectors, as well as the transmittance of beam splitters and the mode mismatch factor between the signal and local oscillating fields on the symbol error rate are separately investigated through Monte Carlo simulations. Using photon-number-resolving detectors (PNRD) instead of on-off detectors, all the effects on the symbol error rate due to the above four imperfections can be suppressed in a certain degree. The finite resolution and PNR capability of PNRDs are also considered. We find that for currently available technology, the receiver shows a reasonable gain from the standard quantum limit (SQL) with moderate stages.
Nonsingular cosmology from evolutionary quantum gravity
Francesco Cianfrani; Giovanni Montani; Fabrizio Pittorino
2014-10-30
We provide a cosmological implementation of the evolutionary quantum gravity, describing an isotropic Universe, in the presence of a negative cosmological constant and a massive (preinflationary) scalar field. We demonstrate that the considered Universe has a nonsingular quantum behavior, associated to a primordial bounce, whose ground state has a high occupation number. Furthermore, in such a vacuum state, the super-Hamiltonian eigenvalue is negative, corresponding to a positive emerging dust energy density. The regularization of the model is performed via a polymer quantum approach to the Universe scale factor and the proper classical limit is then recovered, in agreement with a preinflationary state of the Universe. Since the dust energy density is redshifted by the Universe deSitter phase and the cosmological constant does not enter the ground state eigenvalue, we get a late-time cosmology, compatible with the present observations, endowed with a turning point in the far future.
Fundamental limitations for quantum and nano thermodynamics
Micha? Horodecki; Jonathan Oppenheim
2014-10-25
The relationship between thermodynamics and statistical physics is valid in the thermodynamic limit - when the number of particles becomes very large. Here, we study thermodynamics in the opposite regime - at both the nano scale, and when quantum effects become important. Applying results from quantum information theory we construct a theory of thermodynamics in these limits. We derive general criteria for thermodynamical state transformations, and as special cases, find two free energies: one that quantifies the deterministically extractable work from a small system in contact with a heat bath, and the other that quantifies the reverse process. We find that there are fundamental limitations on work extraction from nonequilibrium states, owing to finite size effects and quantum coherences. This implies that thermodynamical transitions are generically irreversible at this scale. As one application of these methods, we analyse the efficiency of small heat engines and find that they are irreversible during the adiabatic stages of the cycle.
Quantum cryptographic system with reduced data loss
Lo, Hoi-Kwong (1309, Low Block, Lei Moon House Ap Lei Chau Estate, Hong Kong, HK); Chau, Hoi Fung (Flat C, 42nd Floor, Tower 1, University Heights 23 Pokfield Road, Pokfulam, Hong Kong, HK)
1998-01-01
A secure method for distributing a random cryptographic key with reduced data loss. Traditional quantum key distribution systems employ similar probabilities for the different communication modes and thus reject at least half of the transmitted data. The invention substantially reduces the amount of discarded data (those that are encoded and decoded in different communication modes e.g. using different operators) in quantum key distribution without compromising security by using significantly different probabilities for the different communication modes. Data is separated into various sets according to the actual operators used in the encoding and decoding process and the error rate for each set is determined individually. The invention increases the key distribution rate of the BB84 key distribution scheme proposed by Bennett and Brassard in 1984. Using the invention, the key distribution rate increases with the number of quantum signals transmitted and can be doubled asymptotically.
Quantum of optical absorption in two-dimensional semiconductors
California at Berkeley, University of
. Absorptance quantization appears to be universal in 2D systems including IIIV quantum wells and graphene quantitative examination of the intrinsic absorption properties of free-standing 2D semiconductor thin films work has shown that graphene, a 2D semimetal, has a universal value of light absorption, namely , where
Troubles with quantum anisotropic cosmological models: loss of unitarity
F. G. Alvarenga; A. B. Batista; J. C. Fabris; S. V. B. Goncalves
2004-02-25
The anisotropic Bianchi I cosmological model coupled with perfect fluid is quantized in the minisuperspace. The perfect fluid is described by using the Schutz formalism which allows to attribute dynamical degrees of freedom to matter. It is shown that the resulting model is non-unitary. This breaks the equivalence between the many-worlds and dBB interpretations of quantum mechanics.
On the q-quantum gravity loop algebra
Seth Major
2008-02-19
A class of deformations of the q-quantum gravity loop algebra is shown to be incompatible with the combinatorics of Temperley-Lieb recoupling theory with deformation parameter at a root of unity. This incompatibility appears to extend to more general deformation parameters.
Ordinary versus PT-symmetric ?³ quantum field theory
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Bender, Carl M.; Branchina, Vincenzo; Messina, Emanuele
2012-04-02
A quantum-mechanical theory is PT-symmetric if it is described by a Hamiltonian that commutes with PT, where the operator P performs space reflection and the operator T performs time reversal. A PT-symmetric Hamiltonian often has a parametric region of unbroken PT symmetry in which the energy eigenvalues are all real. There may also be a region of broken PT symmetry in which some of the eigenvalues are complex. These regions are separated by a phase transition that has been repeatedly observed in laboratory experiments. This paper focuses on the properties of a PT-symmetric ig?³ quantum field theory. This quantum fieldmore »theory is the analog of the PT-symmetric quantum-mechanical theory described by the Hamiltonian H=p²+ix³, whose eigenvalues have been rigorously shown to be all real. This paper compares the renormalization group properties of a conventional Hermitian g?³ quantum field theory with those of the PT-symmetric ig?³ quantum field theory. It is shown that while the conventional g?³ theory in d=6 dimensions is asymptotically free, the ig?³ theory is like a g?? theory in d=4 dimensions; it is energetically stable, perturbatively renormalizable, and trivial.« less
Plane waves in quantum gravity: breakdown of the classical spacetime
Guillermo A. Mena Marugan; Manuel Montejo
2000-01-11
Starting with the Hamiltonian formulation for spacetimes with two commuting spacelike Killing vectors, we construct a midisuperspace model for linearly polarized plane waves in vacuum gravity. This model has no constraints and its degrees of freedom can be interpreted as an infinite and continuous set of annihilation and creation like variables. We also consider a simplified version of the model, in which the number of modes is restricted to a discrete set. In both cases, the quantization is achieved by introducing a Fock representation. We find regularized operators to represent the metric and discuss whether the coherent states of the quantum theory are peaked around classical spacetimes. It is shown that, although the expectation value of the metric on Killing orbits coincides with a classical solution, its relative fluctuations become significant when one approaches a region where null geodesics are focused. In that region, the spacetimes described by coherent states fail to admit an approximate classical description. This result applies as well to the vacuum of the theory.
A passive transmitter for quantum key distribution with coherent light
Marcos Curty; Marc Jofre; Valerio Pruneri; Morgan W. Mitchell
2011-08-03
Signal state preparation in quantum key distribution schemes can be realized using either an active or a passive source. Passive sources might be valuable in some scenarios; for instance, in those experimental setups operating at high transmission rates, since no externally driven element is required. Typical passive transmitters involve parametric down-conversion. More recently, it has been shown that phase-randomized coherent pulses also allow passive generation of decoy states and Bennett-Brassard 1984 (BB84) polarization signals, though the combination of both setups in a single passive source is cumbersome. In this paper, we present a complete passive transmitter that prepares decoy-state BB84 signals using coherent light. Our method employs sum-frequency generation together with linear optical components and classical photodetectors. In the asymptotic limit of an infinite long experiment, the resulting secret key rate (per pulse) is comparable to the one delivered by an active decoy-state BB84 setup with an infinite number of decoy settings.
Pipeline MT Instructions Identification Number
Hong, Don
Pipeline MT Instructions Identification Number For identification purposes, you will be assigned a special identification number. M# You can activate your MT email, login to PipelineMT to register for classes or pay tuition and fees. Activating the MTSU Email and PipelineMT accounts: Visit the website
Exponential Sensitivity and its Cost in Quantum Physics
András Gilyén; Tamás Kiss; Igor Jex
2015-08-13
State selective protocols, like entanglement purification, lead to an essentially non-linear quantum evolution, unusual in naturally occurring quantum processes. Sensitivity to initial states in quantum systems, stemming from such non-linear dynamics, is a promising perspective for applications. Here we demonstrate that chaotic behaviour is a rather generic feature in state selective protocols: exponential sensitivity can exist for all initial states in an experimentally realisable optical scheme. Moreover, any complex rational polynomial map, including the example of the Mandelbrot set, can be directly realised. In state selective protocols, one needs an ensemble of initial states, the size of which decreases with each iteration. We prove that exponential sensitivity to initial states in any quantum system have to be related to downsizing the initial ensemble also exponentially. Our results show that magnifying initial differences of quantum states (a Schr\\"odinger microscope) is possible, however, there is a strict bound on the number of copies needed.
Is Holographic Entropy and Gravity the result of Quantum Mechanics?
Joakim Munkhammar
2010-03-09
In this paper we suggest a connection between quantum mechanics and Verlinde's recently proposed entropic force theory for the laws of Newton. We propose an entropy based on the quantum mechanical probability density distribution. With the assumption that the holographic principle holds we propose that our suggested quantum entropy generalizes the Bekenstein entropy used by Verlinde in his approach. Based on this assumption we suggest that Verlinde's entropic theory of gravity has a quantum mechanical origin. We establish a reformulation of the Newtonian potential for gravity based on this quantum mechanical entropy. We also discuss the notion of observation and the correspondence to classical physics. Finally we give a discussion, a number of open problems and some concluding remarks.
Quantum Measurements of Scattered Particles
Marco Merkli; Mark Penney
2015-03-20
We investigate the process of quantum measurements on scattered probes. Before scattering, the probes are independent, but they become entangled afterwards, due to the interaction with the scatterer. The collection of measurement results (the history) is a stochastic process of dependent random variables. We link the asymptotic properties of this process to spectral characteristics of the dynamics. We show that the process has decaying time correlations and that a zero-one law holds. We deduce that if the incoming probes are not sharply localized with respect to the spectrum of the measurement operator, then the process does not converge. Nevertheless, the scattering modifies the measurement outcome frequencies, which are shown to be the average of the measurement projection operator, evolved for one interaction period, in an asymptotic state. We illustrate the results on a truncated Jaynes-Cummings model.
Open Quantum Systems at Low Temperature
Johan F. Triana
2015-08-25
It is known that the origin of the deviations from standard thermodynamics proceed from the strong coupling to the bath. Here, it is shown that these deviations are related to the power spectrum of the bath. Specifically, it is shown that the system thermal-equilibrium-state cannot be characterized by the canonical Boltzmann's distribution in quantum mechanics. This is because the uncertainty principle imposed a lower bound of the dispersion of the total energy of the system that is dominated by the spectral density of the bath. However, in the classical case, for a wide class of systems that interact via central forces with pairwise-self-interacting environment, the system thermal equilibrium state is exactly characterized by the canonical Boltzmann distribution. As a consequence of this analysis and taking into account all energy scales in the system and reservoir interaction, an effective coupling to the environment is introduced. Sample computations in different regimes predicted by this effective coupling are shown. Specifically, in the strong coupling effective regime, the system exhibits deviations from standard thermodynamics and in the weak coupling effective regime, quantum features such as stationary entanglement are possible at high temperatures. Moreover, it is known that the spectrum of thermal baths depends on the non-Markovian character. Hence, non-Markovian interactions have a important role in the thermal equilibrium state of physical systems. For example, in quantum optomechanics is looked up to cool the mechanical system through an auxiliary system which generally is a cavity. This cooling process takes into account the non-Markovian interaction and as it is shown here, it is more effective than if we use only the Markovian approximation in the equation of motion for the different modes.
Alan Paris; George Atia; Azadeh Vosoughi; Stephen Berman
2015-10-31
A new class of formal latent-variable stochastic processes called hidden quantum models (HQM's) is defined in order to clarify the theoretical foundations of ion channel signal processing. HQM's are based on quantum stochastic processes which formalize time-dependent observation. They allow the calculation of autocovariance functions which are essential for frequency-domain signal processing. HQM's based on a particular type of observation protocol called independent activated measurements are shown to to be distributionally equivalent to hidden Markov models yet without an underlying physical Markov process. Since the formal Markov processes are non-physical, the theory of activated measurement allows merging energy-based Eyring rate theories of ion channel behavior with the more common phenomenological Markov kinetic schemes to form energy-modulated quantum channels. Using the simplest quantum channel model consistent with neuronal membrane voltage-clamp experiments, activation eigenenergies are calculated for the Hodgkin-Huxley K+ and Na+ ion channels. It is also shown that maximizing entropy under constrained activation energy yields noise spectral densities approximating $S(f) \\sim 1/f^\\alpha$, thus offering a biophysical explanation for the ubiquitous $1/f$-type in neurological signals.
Zeynab Harsij; Behrouz Mirza
2014-09-24
A helicity entangled tripartite state is considered in which the degree of entanglement is preserved in non-inertial frames. It is shown that Quantum Entanglement remains observer independent. As another measure of quantum correlation, Quantum Discord has been investigated. It is explicitly shown that acceleration has no effect on the degree of quantum correlation for the bipartite and tripartite helicity entangled states. Geometric Quantum Discord as a Hilbert-Schmidt distance is computed for helicity entangled states. It is shown that living in non-inertial frames does not make any influence on this distance, either. In addition, the analysis has been extended beyond single mode approximation to show that acceleration does not have any impact on the quantum features in the limit beyond the single mode. As an interesting result, while the density matrix depends on the right and left Unruh modes, the Negativity as a measure of Quantum Entanglement remains constant. Also, Quantum Discord does not change beyond single mode approximation.
Quantum chaos in small quantum networks
Ilki Kim; Guenter Mahler
1999-11-20
We study a 2-spin quantum Turing architecture, in which discrete local rotations \\alpha_m of the Turing head spin alternate with quantum controlled NOT-operations. We show that a single chaotic parameter input \\alpha_m leads to a chaotic dynamics in the entire Hilbert space. The instability of periodic orbits on the Turing head and `chaos swapping' onto the Turing tape are demonstrated explicitly as well as exponential parameter sensitivity of the Bures metric.
Propagation of vector solitons in a quasi-resonant medium with stark deformation of quantum states
Sazonov, S. V., E-mail: sazonov.sergei@gmail.com [National Research Centre Kurchatov Institute (Russian Federation); Ustinov, N. V., E-mail: n_ustinov@mail.ru [Moscow State Railway University, Kaliningrad Branch (Russian Federation)
2012-11-15
The nonlinear dynamics of a vector two-component optical pulse propagating in quasi-resonance conditions in a medium of nonsymmetric quantum objects is investigated for Stark splitting of quantum energy levels by an external electric field. We consider the case when the ordinary component of the optical pulse induces {sigma} transitions, while the extraordinary component induces the {pi} transition and shifts the frequencies of the allowed transitions due to the dynamic Stark effect. It is found that under Zakharov-Benney resonance conditions, the propagation of the optical pulse is accompanied by generation of an electromagnetic pulse in the terahertz band and is described by the vector generalization of the nonlinear Yajima-Oikawa system. It is shown that this system (as well as its formal generalization with an arbitrary number of optical components) is integrable by the inverse scattering transformation method. The corresponding Darboux transformations are found for obtaining multisoliton solutions. The influence of transverse effects on the propagation of vector solitons is investigated. The conditions under which transverse dynamics leads to self-focusing (defocusing) of solitons are determined.
Types of random numbers and Monte Carlo Methods Pseudorandom number generation
Mascagni, Michael
Types of random numbers and Monte Carlo Methods Pseudorandom number generation Quasirandom number generation Conclusions WE246: Random Number Generation A Practitioner's Overview Prof. Michael Mascagni #12;Types of random numbers and Monte Carlo Methods Pseudorandom number generation Quasirandom number
Similarity between quantum mechanics and thermodynamics: Entropy, temperature, and Carnot cycle
Sumiyoshi Abe; Shinji Okuyama
2011-03-04
Similarity between quantum mechanics and thermodynamics is discussed. It is found that if the Clausius equality is imposed on the Shannon entropy and the analogue of the heat quantity, then the value of the Shannon entropy comes to formally coincide with that of the von Neumann entropy of the canonical density matrix, and pure-state quantum mechanics apparently transmutes into quantum thermodynamics. The corresponding quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is studied, and its efficiency is shown to be identical to the classical one.
Similarity between quantum mechanics and thermodynamics: Entropy, temperature, and Carnot cycle
Abe, Sumiyoshi
2010-01-01
Similarity between quantum mechanics and thermodynamics is discussed. It is found that if the Clausius equality is imposed on the Shannon entropy and the analogue of the heat quantity, then the value of the Shannon entropy comes to formally coincide with that of the von Neumann entropy of the canonical density matrix, and pure-state quantum mechanics apparently transmutes into quantum thermodynamics. The corresponding quantum Carnot cycle of a simple two-state model of a particle confined in a one-dimensional infinite potential well is studied, and its efficiency is shown to be identical to the classical one.
Rasio, Frederic A.
2001-01-01
wave sources for LISA. We provide estimates for the numbers of sources of several categories. The detection of these sources would provide information about both binary star evolution and the dynamicsINSTITUTE OF PHYSICS PUBLISHING CLASSICAL AND QUANTUM GRAVITY Class. Quantum Grav. 18 (2001) 4025
Modeling, analysis and control of quantum electronic devices
Zhang, Zhigang
2009-06-02
.99). . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 4.5 Curve of ?b with respect to f, when ?uf = 1010. Parameters are chosen as (4.99). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 4.6 3D mesh of ?b with respect to f and ?uf. Parameters are chosen as (4... gates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.4 The Bloch sphere representation of a quantum state. . . . . . . . . . 13 2.5 Splitting of energy levels of a nucleus with spin quantum number 1/2. 18 2.6 A magnetic field B0...
Probability and complex quantum trajectories
John, Moncy V. [Department of Physics, St. Thomas College, Kozhencherry, Pathanamthitta, Kerala 689 641 (India)], E-mail: moneyjohn@yahoo.co.uk
2009-01-15
It is shown that in the complex trajectory representation of quantum mechanics, the Born's {psi}*{psi} probability density can be obtained from the imaginary part of the velocity field of particles on the real axis. Extending this probability axiom to the complex plane, we first attempt to find a probability density by solving an appropriate conservation equation. The characteristic curves of this conservation equation are found to be the same as the complex paths of particles in the new representation. The boundary condition in this case is that the extended probability density should agree with the quantum probability rule along the real line. For the simple, time-independent, one-dimensional problems worked out here, we find that a conserved probability density can be derived from the velocity field of particles, except in regions where the trajectories were previously suspected to be nonviable. An alternative method to find this probability density in terms of a trajectory integral, which is easier to implement on a computer and useful for single particle solutions, is also presented. Most importantly, we show, by using the complex extension of Schrodinger equation, that the desired conservation equation can be derived from this definition of probability density.
Quantum Simulations for Dense Matter
Ceperley, David M
2010-06-07
High pressure systems are important, for example, to understand the interiors of giant planets (Jupiter and Saturn), for experiments at NIF (the National Ignition Facility at Livermore) related to inertially confined fusion and for other interests of DOE. In this project, we are developing innovative simulation methods (Quantum Monte Carlo methods) to allow more accurate calculation of properties of systems under extreme conditions of pressure and temperature. These methods can use the power of current day supercomputers made of very many processors, starting from the basic equations of physics to model quantum phenomena important at the microscopic scale. During the grant period, we have settled two important questions of the physics of hydrogen and helium under extreme conditions. We have found the pressures and temperatures when hydrogen and helium mix together; this is important to understand the difference of the interiors of the planets Jupiter and Saturn. Secondly, we have shown that there exists a sharp transition as a function of pressure between molecular and atomic liquid hydrogen at temperatures below 2000K. This prediction can be confirmed with high pressure experiments.
Models of quantum computation and quantum programming languages
J. A. Miszczak
2011-12-03
The goal of the presented paper is to provide an introduction to the basic computational models used in quantum information theory. We review various models of quantum Turing machine, quantum circuits and quantum random access machine (QRAM) along with their classical counterparts. We also provide an introduction to quantum programming languages, which are developed using the QRAM model. We review the syntax of several existing quantum programming languages and discuss their features and limitations.
Blind quantum machine learning
Yu-Bo Sheng; Lan Zhou
2015-07-26
Blind quantum machine learning (BQML) enables a classical client with little quantum technology to delegate a remote quantum machine learning to the quantum server in such a approach that the privacy data is preserved. Here we propose the first BQML protocol that the client can classify two-dimensional vectors to different clusters, resorting to a remote small-scale photon quantum computation processor. During the protocol, the client is only required to rotate and measure the single qubit. The protocol is secure without leaking any relevant information to the Eve. Any eavesdropper who attempts to intercept and disturb the learning process can be noticed. In principle, this protocol can be used to classify high dimensional vectors and may provide a new viewpoint and application for quantum machine learning.
Quantum control in spintronics
Ardavan, A
2011-01-01
Superposition and entanglement are uniquely quantum phenomena. Superposition incorporates a phase which contains information surpassing any classical mixture. Entanglement offers correlations between measurements in quantum systems that are stronger than any which would be possible classically. These give quantum computing its spectacular potential, but the implications extend far beyond quantum information processing. Early applications may be found in entanglement enhanced sensing and metrology. Quantum spins in condensed matter offer promising candidates for investigating and exploiting superposition and entanglement, and enormous progress is being made in quantum control of such systems. In GaAs, individual electron spins can be manipulated and measured, and singlet-triplet states can be controlled in double-dot structures. In silicon, individual electron spins can be detected by ionisation of phosphorous donors, and information can be transferred from electron spins to nuclear spins to provide long memor...
Adiabatic graph-state quantum computation
Bobby Antonio; Damian Markham; Janet Anders
2014-12-19
Measurement-based quantum computation (MBQC) and holonomic quantum computation (HQC) are two very different computational methods. The computation in MBQC is driven by adaptive measurements executed in a particular order on a large entangled state. In contrast in HQC the system starts in the ground subspace of a Hamiltonian which is slowly changed such that a transformation occurs within the subspace. Following the approach of Bacon and Flammia, we show that any measurement-based quantum computation on a graph state with \\emph{gflow} can be converted into an adiabatically driven holonomic computation, which we call \\emph{adiabatic graph-state quantum computation} (AGQC). We then investigate how properties of AGQC relate to the properties of MBQC, such as computational depth. We identify a trade-off that can be made between the number of adiabatic steps in AGQC and the norm of $\\dot{H}$ as well as the degree of $H$, in analogy to the trade-off between the number of measurements and classical post-processing seen in MBQC. Finally the effects of performing AGQC with orderings that differ from standard MBQC are investigated.
INSTITUTE for QUANTUM STRUCTURES AND DEVICES
Plotkin, Steven S.
, and #12;the design and fabrication of quantum devices based on magnetic, quantum dot, and superconducting
Some topics in thermodynamics and quantum mechanics
Robert Carroll
2012-11-17
We sketch some connecting relations involving fractional and quantum calculi, fractal structure, thermodynamics, and quantum mechanics.
Wave-Packet Revivals for Quantum Systems with Nondegenerate Energies
Robert Bluhm; Alan Kostelecky; Bogdan Tudose
1996-09-26
The revival structure of wave packets is examined for quantum systems having energies that depend on two nondegenerate quantum numbers. For such systems, the evolution of the wave packet is controlled by two classical periods and three revival times. These wave packets exhibit quantum beats in the initial motion as well as new types of long-term revivals. The issue of whether fractional revivals can form is addressed. We present an analytical proof showing that at certain times equal to rational fractions of the revival times the wave packet can reform as a sum of subsidiary waves and that both conventional and new types of fractional revivals can occur.
Plasmon modes of metallic nanowires including quantum nonlocal effects
Moradi, Afshin
2015-03-15
The properties of electrostatic surface and bulk plasmon modes of cylindrical metallic nanowires are investigated, using the quantum hydrodynamic theory of plasmon excitation which allows an analytical study of quantum tunneling effects through the Bohm potential term. New dispersion relations are obtained for each type of mode and their differences with previous treatments based on the standard hydrodynamic model are analyzed in detail. Numerical results show by considering the quantum effects, as the value of wave number increases, the surface modes are slightly red-shifted first and then blue-shifted while the bulk modes are blue-shifted.
Noise, sampling, and the number of projections in cone-beam CT with a flat-panel detector
Zhao, Z.; Gang, G. J.; Siewerdsen, J. H.
2014-06-15
Purpose: To investigate the effect of the number of projection views on image noise in cone-beam CT (CBCT) with a flat-panel detector. Methods: This fairly fundamental consideration in CBCT system design and operation was addressed experimentally (using a phantom presenting a uniform medium as well as statistically motivated “clutter”) and theoretically (using a cascaded systems model describing CBCT noise) to elucidate the contributing factors of quantum noise (?{sub Q}), electronic noise (?{sub E}), and view aliasing (?{sub view}). Analysis included investigation of the noise, noise-power spectrum, and modulation transfer function as a function of the number of projections (N{sub proj}), dose (D{sub tot}), and voxel size (b{sub vox}). Results: The results reveal a nonmonotonic relationship between image noise andN{sub proj} at fixed total dose: for the CBCT system considered, noise decreased with increasing N{sub proj} due to reduction of view sampling effects in the regime N{sub proj} shown to depend on the heterogeneity of the object in a direct analytical relationship to power-law anatomical clutter of the form ?/f?{sup ?}—and a general model of individual noise components (?{sub Q}, ?{sub E}, and ?{sub view}) demonstrated agreement with measurements over a broad range in N{sub proj}, D{sub tot}, and b{sub vox}. Conclusions: The work elucidates fairly basic elements of CBCT noise in a manner that demonstrates the role of distinct noise components (viz., quantum, electronic, and view sampling noise). For configurations fairly typical of CBCT with a flat-panel detector (FPD), the analysis reveals a “sweet spot” (i.e., minimum noise) in the rangeN{sub proj} ? 250–350, nearly an order of magnitude lower in N{sub proj} than typical of multidetector CT, owing to the relatively high electronic noise in FPDs. The analysis explicitly relates view aliasing and quantum noise in a manner that includes aspects of the object (“clutter”) and imaging chain (including nonidealities of detector blur and electronic noise) to provide a more rigorous basis for commonly held intuition and heurism in CBCT system design and operation.
Part I Taxpayer Identification Number (TIN) Enter your TIN in the appropriate box. The TIN provided To : Requester Payroll Department Form W-9 Request for Taxpayer Identification Number and Certification. The number shown on this form is my correct taxpayer identification number (or I am waiting for a number
Quantum problem solving as simultaneous computation
Giuseppe Castagnoli
2007-10-09
I provide an alternative way of seeing quantum computation. First, I describe an idealized classical problem solving machine that, thanks to a many body interaction, reversibly and nondeterministically produces the solution of the problem under the simultaneous influence of all the problem constraints. This requires a perfectly accurate, rigid, and reversible relation between the coordinates of the machine parts - the machine can be considered the many body generalization of another perfect machine, the bounching ball model of reversible computation. The mathematical description of the machine, as it is, is applicable to quantum problem solving, an extension of the quantum algorithms that comprises the physical representation of the problem-solution interdependence. The perfect relation between the coordinates of the machine parts is transferred to the populations of the reduced density operators of the parts of the computer register. The solution of the problem is reversibly and nondeterministically produced under the simultaneous influence of the state before measurement and the quantum principle. At the light of the present notion of simultaneous computation, the quantum speed up turns out to be "precognition" of the solution, namely the reduction of the initial ignorance of the solution due to backdating, to before running the algorithm, a time-symmetric part of the state vector reduction on the solution; as such, it is bounded by state vector reduction through an entropic inequality. PACS numbers: 03.67.Lx, 01.55.+b, 01.70.+w
Karim Noui
2010-03-31
We tackle the question of motion in Quantum Gravity: what does motion mean at the Planck scale? Although we are still far from a complete answer we consider here a toy model in which the problem can be formulated and resolved precisely. The setting of the toy model is three dimensional Euclidean gravity. Before studying the model in detail, we argue that Loop Quantum Gravity may provide a very useful approach when discussing the question of motion in Quantum Gravity.
Secure Quantum Key Distribution
Hoi-Kwong Lo; Marcos Curty; Kiyoshi Tamaki
2015-05-20
Secure communication plays a crucial role in the Internet Age. Quantum mechanics may revolutionise cryptography as we know it today. In this Review Article, we introduce the motivation and the current state of the art of research in quantum cryptography. In particular, we discuss the present security model together with its assumptions, strengths and weaknesses. After a brief introduction to recent experimental progress and challenges, we survey the latest developments in quantum hacking and counter-measures against it.
Are Quantum States Subjective?
R. K. Pradhan
2012-02-22
The subjective nature of the quantum states is brought out and it is argued that the objective state assignment is subsequent to the subjective state of the observer regarding his state of knowledge about the system. The collapse postulate is examined in detail to bring out the inherent subjectivity of the quantum state. The role of doubt and faith in quantum state assignment is examined.
Quantum information science as an approach to complex quantum systems
Michael A. Nielsen
2002-08-13
What makes quantum information science a science? These notes explore the idea that quantum information science may offer a powerful approach to the study of complex quantum systems. We discuss how to quantify complexity in quantum systems, and argue that there are two qualitatively different types of complex quantum system. We also explore ways of understanding complex quantum dynamics by quantifying the strength of a quantum dynamical operation as a physical resource. This is the text for a talk at the ``Sixth International Conference on Quantum Communication, Measurement and Computing'', held at MIT, July 2002. Viewgraphs for the talk may be found at http://www.qinfo.org/talks/.
Scalable cavity quantum electrodynamics system for quantum computing
Mohammad Hasan Aram; Sina Khorasani
2015-07-18
We introduce a new scalable cavity quantum electrodynamics platform which can be used for quantum computing. This system is composed of coupled photonic crystal (PC) cavities which their modes lie on a Dirac cone in the whole super crystal band structure. Quantum information is stored in quantum dots that are positioned inside the cavities. We show if there is just one quantum dot in the system, energy as photon is exchanged between the quantum dot and the Dirac modes sinusoidally. Meanwhile the quantum dot becomes entangled with Dirac modes. If we insert more quantum dots into the system, they also become entangled with each other.
Quantum gravity on the lattice
Hamber, Herbert W.
2009-01-01
the Conference Quantum Gravity: Challenges and Perspectives.divergences in quantum gravity. In: Hawking, S.W. , Israel,f ) V n?1 ( f ) = Quantum gravity on the lattice Similarly,
FOURIER TRANSFORM MULTIPLE QUANTUM NMR
Drobny, G.
2011-01-01
of transition observed in Fourier transform multiple quantumDecember 18-19, 1979 FOURIER TRANSFORM MULTIPLE QUANTUM NMRof London, December 1978. FOURIER TRANSFO~~ MULTIPLE QUANTUM
Vacuum Energy in Quantum Graphs
Wilson, Justin
2007-07-14
We calculate the vacuum energy in quantum graphs. Vacuum energy arose in quantum physics but has an independent mathematical interest as a functional carrying information about the eigenvalue spectrum of a system. A quantum graph is a metric graph...
A quantum way for metamaterials
Didier Felbacq
2011-03-09
A new future for metamaterials is suggested, involving the insertion of quantum degrees of freedom, under the guise of quantum dots or cold atoms, in an photonic matrix. It is argued that new emergent, quantum, properties could be obtained.
Coherent control of quantum information
Henry, Michael Kevin
2006-01-01
Quantum computation requires the ability to efficiently control quantum information in the presence of noise. In this thesis, NMR quantum information processors (QIPs) are used to study noise processes that compromise ...
Reverse Engineering Quantum Field Theory
Robert Oeckl
2012-10-02
An approach to the foundations of quantum theory is advertised that proceeds by "reverse engineering" quantum field theory. As a concrete instance of this approach, the general boundary formulation of quantum theory is outlined.
Construction and Optimization of the Quantum Analog of Carnot Cycles
Gaoyang Xiao; Jiangbin Gong
2015-03-03
The quantum analog of Carnot cycles in few-particle systems consists of two quantum adiabatic steps and two isothermal steps. This construction is formally justified by use of a minimum work principle. It is then shown, without relying on any microscopic interpretations of work or heat, that the heat-to-work efficiency of the quantum Carnot cycle thus constructed may be further optimized, provided that two conditions regarding the expectation value of some generalized force operators evaluated at equilibrium states are satisfied. In general the optimized efficiency is system-specific, lower than the Carnot efficiency, and dependent upon both temperatures of the cold and hot reservoirs. Simple computational examples are used to illustrate our theory. The results should be an important guide towards the design of favorable working conditions of a realistic quantum heat engine.
Real-world Quantum Sensors: Evaluating Resources for Precision Measurement
Nicholas Thomas-Peter; Brian J Smith; Animesh Datta; Lijian Zhang; Uwe Dorner; Ian A Walmsley
2011-05-19
Quantum physics holds the promise of enabling certain tasks with better performance than possible when only classical resources are employed. The quantum phenomena present in many experiments signify nonclassical behavior, but do not always imply superior performance. Quantifying the enhancement achieved from quantum behavior requires careful analysis of the resources involved. We analyze the specific case of parameter estimation using an optical interferometer, where increased precision can be achieved using quantum probe states. Common performance measures are examined and it is shown that some overestimate the improvement. For the simplest experimental case we compare the different measures and show this overestimate explicitly. We give the preferred analysis of real-world experiments and calculate benchmark values for experimental parameters necessary to realize a precision enhancement.
Quantum phase transitions in Bose-Fermi systems
Petrellis, D.; Leviatan, A.; Iachello, F.
2011-04-15
Research Highlights: > We study quantum phase transitions in a system of N bosons and a single-j fermion. > Classical order parameters and correlation diagrams of quantum levels are determined. > The odd fermion strongly influences the location and nature of the phase transition. > Experimental evidence for the U(5)-SU(3) transition in odd-even nuclei is presented. - Abstract: Quantum phase transitions in a system of N bosons with angular momentum L = 0, 2 (s, d) and a single fermion with angular momentum j are investigated both classically and quantum mechanically. It is shown that the presence of the odd fermion strongly influences the location and nature of the phase transition, especially the critical value of the control parameter at which the phase transition occurs. Experimental evidence for the U(5)-SU(3) (spherical to axially-deformed) transition in odd-even nuclei is presented.
Hyperdiffusion of quantum waves in random photonic lattices
Alexander Iomin
2015-08-24
A quantum-mechanical analysis of hyper-fast (faster than ballistic) diffusion of a quantum wave packet in random optical lattices is presented. The main motivation of the presented analysis is experimental demonstrations of hyper-diffusive spreading of a wave packet in random photonic lattices [L. Levi \\textit{et al.}, Nature Phys. \\textbf{8}, 912 (2012)]. A rigorous quantum-mechanical calculation of the mean probability amplitude is suggested, and it is shown that the power law spreading of the mean squared displacement (MSD) is $\\sim t^{\\alpha}$, where $2potential $V(x,t)$, which describes random inhomogeneities of the medium. In particular, when the random potential is $\\delta$ correlated in time, the quantum wave packet spreads according Richardson turbulent diffusion with the MSD $\\sim t^3$. Hyper-diffusion with $\\alpha=12/5$ is also obtained for arbitrary correlation properties of the random potential.
Hyperdiffusion of quantum waves in random photonic lattices
Iomin, Alexander
2015-01-01
A quantum-mechanical analysis of hyper-fast (faster than ballistic) diffusion of a quantum wave packet in random optical lattices is presented. The main motivation of the presented analysis is experimental demonstrations of hyper-diffusive spreading of a wave packet in random photonic lattices [L. Levi \\textit{et al.}, Nature Phys. \\textbf{8}, 912 (2012)]. A rigorous quantum-mechanical calculation of the mean probability amplitude is suggested, and it is shown that the power law spreading of the mean squared displacement (MSD) is $\\sim t^{\\alpha}$, where $2potential $V(x,t)$, which describes random inhomogeneities of the medium. In particular, when the random potential is $\\delta$ correlated in time, the quantum wave packet spreads according Richardson turbulent diffusion with the MSD $\\sim t^3$. Hyper-diffusion with $\\alpha=12/5$ is also obtained for arbitrary correlation properties of the rand...
A Signed Particle Formulation of Non-Relativistic Quantum Mechanics
Sellier, Jean Michel
2015-01-01
A formulation of non-relativistic quantum mechanics in terms of Newtonian particles is presented in the shape of a set of three postulates. In this new theory, quantum systems are described by ensembles of signed particles which behave as field-less classical objects which carry a negative or positive sign and interact with an external potential by means of creation and annihilation events only. This approach is shown to be a generalization of the signed particle Wigner Monte Carlo method which reconstructs the time-dependent Wigner quasi-distribution function of a system and, therefore, the corresponding Schroedinger time-dependent wave-function. Its classical limit is discussed and a physical interpretation, based on experimental evidences coming from quantum tomography, is suggested. Moreover, in order to show the advantages brought by this novel formulation, a straightforward extension to relativistic effects is discussed. To conclude, quantum tunnelling numerical experiments are performed to show the val...
Quantum dot conjugates in a sub-micrometer fluidic channel
Stavis, Samuel M.; Edel, Joshua B.; Samiee, Kevan T.; Craighead, Harold G.
2010-04-13
A nanofluidic channel fabricated in fused silica with an approximately 500 nm square cross section was used to isolate, detect and identify individual quantum dot conjugates. The channel enables the rapid detection of every fluorescent entity in solution. A laser of selected wavelength was used to excite multiple species of quantum dots and organic molecules, and the emission spectra were resolved without significant signal rejection. Quantum dots were then conjugated with organic molecules and detected to demonstrate efficient multicolor detection. PCH was used to analyze coincident detection and to characterize the degree of binding. The use of a small fluidic channel to detect quantum dots as fluorescent labels was shown to be an efficient technique for multiplexed single molecule studies. Detection of single molecule binding events has a variety of applications including high throughput immunoassays.
Quantum tunneling resonant electron transfer process in Lorentzian plasmas
Hong, Woo-Pyo; Jung, Young-Dae
2014-08-15
The quantum tunneling resonant electron transfer process between a positive ion and a neutral atom collision is investigated in nonthermal generalized Lorentzian plasmas. The result shows that the nonthermal effect enhances the resonant electron transfer cross section in Lorentzian plasmas. It is found that the nonthermal effect on the classical resonant electron transfer cross section is more significant than that on the quantum tunneling resonant charge transfer cross section. It is shown that the nonthermal effect on the resonant electron transfer cross section decreases with an increase of the Debye length. In addition, the nonthermal effect on the quantum tunneling resonant electron transfer cross section decreases with increasing collision energy. The variation of nonthermal and plasma shielding effects on the quantum tunneling resonant electron transfer process is also discussed.
Quantum Interference Induced Photon Blockade in a Coupled Single Quantum Dot-Cavity System
Tang, Jing; Xu, Xiulai
2015-01-01
We propose an experimental scheme to implement a strong photon blockade with a single quantum dot coupled to a nanocavity. The photon blockade effect can be tremendously enhanced by driving the cavity and the quantum dot simultaneously with two classical laser fields. This enhancement of photon blockade is ascribed to the quantum interference effect to avoid two-photon excitation of the cavity field. Comparing with Jaynes-Cummings model, the second-order correlation function at zero time delay $g^{(2)}(0)$ in our scheme can be reduced by two orders of magnitude and the system sustains a large intracavity photon number. A red (blue) cavity-light detuning asymmetry for photon quantum statistics with bunching or antibunching characteristics is also observed. The photon blockade effect has a controllable flexibility by tuning the relative phase between the two pumping laser fields and the Rabi coupling strength between the quantum dot and the pumping field. Moreover, the photon blockade scheme based on quantum in...
Quantum leap: how to complete a quantum walk in a single step
Magdalena Stobi?ska; Peter P. Rohde; Pawe? Kurzy?ski
2015-11-02
Quantum walks provide simple models of various fundamental processes. It is pivotal to know when the dynamics underlying a walk lead to quantum advantages just by examining its statistics. A walk with many indistinguishable particles and measurements of non-classical multi-particle correlations is likely to reveal the quantum nature. The number of elements $O(n)$ in a setup realizing walks grows with their length or spread $n$. We introduce the concept of a quantum leap, a process which can be achieved with fewer or complementary resources and which in a single step simulates another long process. The process and its leap are described by the same Hamiltonian but, the latter parametrizes the evolution with a tunable parameter of a setup. In the case of walks, a leap immediately gives a probability distribution which results only after many steps. This may be appealing for simulation of processes which are lengthy or require dynamical control. We discuss a leap based on the multi-particle Hong--Ou--Mandel interference, an inherently quantum phenomenon. It reproduces a quantum walk enabling perfect state transfer through spin chains. It requires a beam splitter, two detectors and $n$ particles to mimic a walk on a chain of size $O(n)$, for time fixed by beam-splitter's reflectivity. Our results apply to a broad class of systems where the HOM-like effects can be observed, and may constitute a new approach to simulation of complex Hamiltonians with passive interferometers.
Jianwei Wang; Damien Bonneau; Matteo Villa; Joshua W. Silverstone; Raffaele Santagati; Shigehito Miki; Taro Yamashita; Mikio Fujiwara; Masahide Sasaki; Hirotaka Terai; Michael G. Tanner; Chandra M. Natarajan; Robert H. Hadfield; Jeremy L. O'Brien; Mark G. Thompson
2015-09-26
Integrated photonics has enabled much progress towards quantum technologies. Many applications, including quantum communication, sensing, and distributed and cloud quantum computing, will require coherent photonic interconnection between separate chip-based sub-systems. Large-scale quantum computing systems and architectures may ultimately require quantum interconnects to enable scaling beyond the limits of a single wafer and towards "multi-chip" systems. However, coherently interconnecting separate chips is challenging due to the fragility of these quantum states and the demanding challenges of transmitting photons in at least two media within a single coherent system. Distribution and manipulation of qubit entanglement between multiple devices is one of the most stringent requirements of the interconnected system. Here, we report a quantum photonic interconnect demonstrating high-fidelity entanglement distribution and manipulation between two separate chips, implemented using state-of-the-art silicon photonics. Path-entangled states are generated and manipulated on-chip, and distributed between the chips by interconverting between path-encoding and polarisation-encoding. We use integrated state analysers to confirm a Bell-type violation of $S$=2.638+-0.039 between two chips. With improvements in loss, this quantum interconnect will provide new levels of flexible systems and architectures for quantum technologies.
Observables on Quantum Structures
Anatolij Dvure?enskij; Mária Kuková
2012-04-29
An observable on a quantum structure is any $\\sigma$-homomorphism of quantum structures from the Borel $\\sigma$-algebra into the quantum structure. We show that our partial information on an observable known only for all intervals of the form $(-\\infty,t)$ is sufficient to determine uniquely the whole observable defined on quantum structures like $\\sigma$-MV-algebras, $\\sigma$-effect algebras, Boolean $\\sigma$-algebras, monotone $\\sigma$-complete effect algebras with the Riesz Decomposition Property, the effect algebra of effect operators of a Hilbert space, and a system of functions, and an effect-tribe.