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

Title: Experimental procedures for entanglement verification

Abstract

We give an overview of different types of entanglement that can be generated in experiments, as well as of various protocols that can be used to verify or quantify entanglement. We propose several criteria that, we argue, should be applied to experimental entanglement verification procedures. Explicit examples demonstrate that not following these criteria will tend to result in overestimating the amount of entanglement generated in an experiment or in inferring entanglement when there is none. We distinguish protocols meant to refute or eliminate hidden-variable models from those meant to verify entanglement.

Authors:
 [1];  [2];  [3];  [4];  [2]
  1. Department of Physics, Oregon Center for Optics and Institute for Theoretical Science, University of Oregon, Eugene, Oregon 97403 (United States)
  2. (United States)
  3. Institute of Quantum Computing and Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (Canada)
  4. Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125 (United States)
Publication Date:
OSTI Identifier:
20982487
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevA.75.052318; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; HIDDEN VARIABLES; INFORMATION THEORY; QUANTUM COMPUTERS; QUANTUM CRYPTOGRAPHY; QUANTUM ENTANGLEMENT; QUANTUM MECHANICS; QUANTUM TELEPORTATION; VERIFICATION

Citation Formats

Enk, S. J. van, Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125, Luetkenhaus, N., Kimble, H. J., and Norman Bridge Laboratory of Physics 12-33, California Institute of Technology, Pasadena, California 91125. Experimental procedures for entanglement verification. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.052318.
Enk, S. J. van, Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125, Luetkenhaus, N., Kimble, H. J., & Norman Bridge Laboratory of Physics 12-33, California Institute of Technology, Pasadena, California 91125. Experimental procedures for entanglement verification. United States. doi:10.1103/PHYSREVA.75.052318.
Enk, S. J. van, Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125, Luetkenhaus, N., Kimble, H. J., and Norman Bridge Laboratory of Physics 12-33, California Institute of Technology, Pasadena, California 91125. Tue . "Experimental procedures for entanglement verification". United States. doi:10.1103/PHYSREVA.75.052318.
@article{osti_20982487,
title = {Experimental procedures for entanglement verification},
author = {Enk, S. J. van and Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125 and Luetkenhaus, N. and Kimble, H. J. and Norman Bridge Laboratory of Physics 12-33, California Institute of Technology, Pasadena, California 91125},
abstractNote = {We give an overview of different types of entanglement that can be generated in experiments, as well as of various protocols that can be used to verify or quantify entanglement. We propose several criteria that, we argue, should be applied to experimental entanglement verification procedures. Explicit examples demonstrate that not following these criteria will tend to result in overestimating the amount of entanglement generated in an experiment or in inferring entanglement when there is none. We distinguish protocols meant to refute or eliminate hidden-variable models from those meant to verify entanglement.},
doi = {10.1103/PHYSREVA.75.052318},
journal = {Physical Review. A},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • We consider entanglement detection for quantum-key-distribution systems that use two signal states and continuous-variable measurements. This problem can be formulated as a separability problem in a qubit-mode system. To verify entanglement, we introduce an object that combines the covariance matrix of the mode with the density matrix of the qubit. We derive necessary separability criteria for this scenario. These criteria can be readily evaluated using semidefinite programming and we apply them to the specific quantum key distribution protocol.
  • We propose methods of fidelity estimation and entanglement verification for experimentally produced four-qubit cluster states. We show that we can obtain a high lower bound of the fidelity using only four local projective measurement settings. The lower bound is close to the exact fidelity, which is determined only by at least nine local projective measurement settings. We also present witness operators for distinguishing entanglement around a four-qubit cluster state from specific classes of genuine four-qubit entanglement, e.g., a class including GHZ and W types of entanglement.
  • Many protocols and experiments in quantum information science are described in terms of simple measurements on qubits. However in a real implementation the exact description is more difficult and more complicated observables are used. The question arises whether a claim of entanglement in the simplified description still holds, if the difference between the realistic and simplified models is taken into account. We show that a positive entanglement statement remains valid if a certain positive linear map connecting the two descriptions--a so-called squashing operation--exists; then lower bounds on the amount of entanglement are also possible. We apply our results to polarizationmore » measurements of photons using only threshold detectors, and derive procedures under which multiphoton events can be neglected.« less
  • Procedures and techniques developed for the negative pi-meson (pion) radiotherapy program at the Los Alamos Meson Physics Facility, Los Alamos, NM, are reviewed and described. A particular pion patient is followed through the entire planning and treatment sequence to describe CT scanning procedures, bolus and collimator and treatment techniques developed to minimize positioning errors (less than 5 mm). Comparison of 2-D and 3-d isodose calculation developed at Los Alamos showed differences of less than 10% attributable to multiple scattering effects and the computational models used. Treatment verification methods using in vivo ion chamber dosimetry generally confirmed the prescribed dose deliverymore » within 10% and using TLD within 18%.« less
  • Implementing energy conservation measures in buildings can reduce energy costs and environmental impacts, but such measures cost money to implement so intelligent investment strategies require the ability to quantify the energy savings by comparing actual energy used to how much energy would have been used in absence of the conservation measures (known as the baseline energy use). Methods exist for predicting baseline energy use, but a limitation of most statistical methods reported in the literature is inadequate quantification of the uncertainty in baseline energy use predictions. However, estimation of uncertainty is essential for weighing the risks of investing in retrofits.more » Most commercial buildings have, or soon will have, electricity meters capable of providing data at short time intervals. These data provide new opportunities to quantify uncertainty in baseline predictions, and to do so after shorter measurement durations than are traditionally used. In this paper, we show that uncertainty estimation provides greater measurement and verification (M&V) information and helps to overcome some of the difficulties with deciding how much data is needed to develop baseline models and to confirm energy savings. We also show that cross-validation is an effective method for computing uncertainty. In so doing, we extend a simple regression-based method of predicting energy use using short-interval meter data. We demonstrate the methods by predicting energy use in 17 real commercial buildings. We discuss the benefits of uncertainty estimates which can provide actionable decision making information for investing in energy conservation measures.« less