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Title: Measure of quantum correlations that lies approximately between entanglement and discord

Abstract

When a quantum system is divided into two local subsystems, measurements on the two subsystems can exhibit correlations beyond those possible in a classical joint probability distribution; these are partially explained by entanglement, and more generally by a wider class of measures such as the quantum discord. In this paper, I introduce a simple thought experiment defining a measure of quantum correlations, which I call the accord, and write the result as a minimax optimization over unitary matrices. I find the exact result for pure states as a simple function of the Schmidt coefficients and provide a complete proof, and I likewise provide and prove the result for several classes of mixed states, notably including all states of two qubits and the experimentally relevant case of a pure state mixed with colorless noise. I demonstrate that for two qubit states the accord provides a tight lower bound on the discord; for Bell diagonal states it is also an upper bound on entanglement.

Authors:
 [1]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1542423
Alternate Identifier(s):
OSTI ID: 1546231
Grant/Contract Number:  
AC02-05CH11231; AC02-05-CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review A
Additional Journal Information:
Journal Volume: 99; Journal Issue: 6; Journal ID: ISSN 2469-9926
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS

Citation Formats

Szasz, Aaron. Measure of quantum correlations that lies approximately between entanglement and discord. United States: N. p., 2019. Web. doi:10.1103/physreva.99.062313.
Szasz, Aaron. Measure of quantum correlations that lies approximately between entanglement and discord. United States. doi:10.1103/physreva.99.062313.
Szasz, Aaron. Wed . "Measure of quantum correlations that lies approximately between entanglement and discord". United States. doi:10.1103/physreva.99.062313.
@article{osti_1542423,
title = {Measure of quantum correlations that lies approximately between entanglement and discord},
author = {Szasz, Aaron},
abstractNote = {When a quantum system is divided into two local subsystems, measurements on the two subsystems can exhibit correlations beyond those possible in a classical joint probability distribution; these are partially explained by entanglement, and more generally by a wider class of measures such as the quantum discord. In this paper, I introduce a simple thought experiment defining a measure of quantum correlations, which I call the accord, and write the result as a minimax optimization over unitary matrices. I find the exact result for pure states as a simple function of the Schmidt coefficients and provide a complete proof, and I likewise provide and prove the result for several classes of mixed states, notably including all states of two qubits and the experimentally relevant case of a pure state mixed with colorless noise. I demonstrate that for two qubit states the accord provides a tight lower bound on the discord; for Bell diagonal states it is also an upper bound on entanglement.},
doi = {10.1103/physreva.99.062313},
journal = {Physical Review A},
number = 6,
volume = 99,
place = {United States},
year = {2019},
month = {6}
}

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