skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Entanglement of a qubit coupled to a resonator in the adiabatic regime

Abstract

We discuss the ground state entanglement of a bi-partite system, composed by a qubit strongly interacting with an oscillator mode, as a function of the coupling strength, the transition frequency and the level asymmetry of the qubit. This is done in the adiabatic regime in which the time evolution of the qubit is much faster than the oscillator one. Within the adiabatic approximation, we obtain a complete characterization of the ground state properties of the system and of its entanglement content.

Authors:
;  [1]; ;  [1];  [2]
  1. Dipartimento di Fisica, Universita della Calabria, 87036 Arcavacata di Rende (Serbia and Montenegro) (Italy)
  2. (Serbia and Montenegro) (Italy)
Publication Date:
OSTI Identifier:
20786895
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 73; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevA.73.032346; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ADIABATIC APPROXIMATION; ASYMMETRY; COUPLING; GROUND STATES; OSCILLATORS; QUANTUM COMPUTERS; QUANTUM ENTANGLEMENT; QUBITS; RESONATORS

Citation Formats

Liberti, Giuseppe, Piperno, Franco, Zaffino, Rosa Letizia, Plastina, Francesco, and INFN-Gruppo collegato di Cosenza, 87036 Arcavacata di Rende. Entanglement of a qubit coupled to a resonator in the adiabatic regime. United States: N. p., 2006. Web. doi:10.1103/PHYSREVA.73.0.
Liberti, Giuseppe, Piperno, Franco, Zaffino, Rosa Letizia, Plastina, Francesco, & INFN-Gruppo collegato di Cosenza, 87036 Arcavacata di Rende. Entanglement of a qubit coupled to a resonator in the adiabatic regime. United States. doi:10.1103/PHYSREVA.73.0.
Liberti, Giuseppe, Piperno, Franco, Zaffino, Rosa Letizia, Plastina, Francesco, and INFN-Gruppo collegato di Cosenza, 87036 Arcavacata di Rende. Wed . "Entanglement of a qubit coupled to a resonator in the adiabatic regime". United States. doi:10.1103/PHYSREVA.73.0.
@article{osti_20786895,
title = {Entanglement of a qubit coupled to a resonator in the adiabatic regime},
author = {Liberti, Giuseppe and Piperno, Franco and Zaffino, Rosa Letizia and Plastina, Francesco and INFN-Gruppo collegato di Cosenza, 87036 Arcavacata di Rende},
abstractNote = {We discuss the ground state entanglement of a bi-partite system, composed by a qubit strongly interacting with an oscillator mode, as a function of the coupling strength, the transition frequency and the level asymmetry of the qubit. This is done in the adiabatic regime in which the time evolution of the qubit is much faster than the oscillator one. Within the adiabatic approximation, we obtain a complete characterization of the ground state properties of the system and of its entanglement content.},
doi = {10.1103/PHYSREVA.73.0},
journal = {Physical Review. A},
number = 3,
volume = 73,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • We demonstrate experimentally the creation and measurement of an entangled state between a microscopic two-level system (TLS), formed by a defect in an oxide layer, and a macroscopic superconducting resonator, where their indirect interaction is mediated by an artificial atom, a superconducting persistent current qubit (PCQB). Under appropriate conditions, we found the coherence time of the TLS, the resonator, and the entangled state of these two are significantly longer than the Ramsey dephasing time of PCQB itself. This demonstrates that a PCQB can be used as a quantum transformer to address high coherence microscopic quantum memories by connecting them tomore » macroscopic quantum buses.« less
  • We consider a simple model of a Josephson junction phase qubit coupled to a solid-state nanoelectromechanical resonator. This and many related qubit-resonator models are analogous to an atom in an electromagnetic cavity. When the systems are weakly coupled and nearly resonant, the dynamics is accurately described by the rotating-wave approximation (RWA) or the Jaynes-Cummings model of quantum optics. However, the desire to develop faster quantum-information-processing protocols necessitates approximate, yet analytic descriptions that are valid for more strongly coupled qubit-resonator systems. Here we present a simple theoretical technique, using a basis of dressed states, to perturbatively account for the leading-order correctionsmore » to the RWA. By comparison with exact numerical results, we demonstrate that the method is accurate for moderately strong coupling and provides a useful theoretical tool for describing fast quantum information processing. The method applies to any quantum two-level system linearly coupled to a harmonic oscillator or single-mode boson field.« less
  • We present a way to realize an n-qubit controlled phase gate with superconducting quantum-interference devices (SQUIDs) by coupling them to a superconducting resonator. In this proposal, the two logical states of a qubit are represented by the two lowest levels of a SQUID. An intermediate level of each SQUID is utilized to facilitate coherent control and manipulation of quantum states of the qubits. It is interesting to note that an n-qubit controlled phase gate can be achieved with n SQUIDs by successively applying a {pi}/2 Jaynes-Cummings pulse to each of the n-1 control SQUIDs before and after a {pi} Jaynes-Cummingsmore » pulse on the target SQUID.« less
  • We study entanglement generation in a pair of qubits interacting with an initially correlated system. Using time-independent perturbation theory and the adiabatic theorem, we show conditions under which the qubits become entangled as the joint system evolves into the ground state of the interacting theory. We then apply these results to the case of qubits interacting with a scalar quantum field. We study three different variations of this setup; a quantum field subject to Dirichlet boundary conditions, a quantum field interacting with a classical potential, and a quantum field that starts in a thermal state.
  • In this paper, we consider the generation of a three-qubit Greenberger-Horne-Zeilinger-like thermal state by applying the entanglement swapping scheme of Zukowski et al. [Ann. N. Y. Acad. Sci. 755, 91 (1995)] to three pairs of two-qubit Heisenberg XY chains. The quality of the resulting three-qubit entanglement is studied by analyzing the teleportation fidelity, when it is used as a resource in the teleportation protocol of Karlsson et al. [Phys. Rev. A 58, 4394 (1998)]. We show that even though thermal noise in the original two-qubit states is amplified by the entanglement swapping process, we are still able to achieve nonclassicalmore » fidelities for the anisotropic Heisenberg XY chains at finitely higher and higher temperatures by adjusting the strengths of an external magnetic field. This has a positive implication on the solid-state realization of a quantum computer.« less