Quantum discord for twoqubit X states
Abstract
Quantum discord, a kind of quantum correlation, is defined as the difference between quantum mutual information and classical correlation in a bipartite system. In general, this correlation is different from entanglement, and quantum discord may be nonzero even for certain separable states. Even in the simple case of bipartite quantum systems, this different kind of quantum correlation has interesting and significant applications in quantum information processing. So far, quantum discord has been calculated explicitly only for a rather limited set of twoqubit quantum states and expressions for more general quantum states are not known. In this article, we derive explicit expressions for quantum discord for a larger class of twoqubit states, namely, a sevenparameter family of so called X states that have been of interest in a variety of contexts in the field. We also study the relation between quantum discord, classical correlation, and entanglement for a number of twoqubit states to demonstrate that they are independent measures of correlation with no simple relative ordering between them.
 Authors:

 Institut fuer Angewandte Physik, Technische Universitaet Darmstadt, Darmstadt D64289 (Germany)
 Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)
 Publication Date:
 OSTI Identifier:
 21413321
 Resource Type:
 Journal Article
 Journal Name:
 Physical Review. A
 Additional Journal Information:
 Journal Volume: 81; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevA.81.042105; (c) 2010 The American Physical Society; Journal ID: ISSN 10502947
 Country of Publication:
 United States
 Language:
 English
 Subject:
 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CORRELATIONS; PROCESSING; QUANTUM ENTANGLEMENT; QUANTUM INFORMATION; INFORMATION
Citation Formats
Ali, Mazhar, Department of Electrical Engineering, COMSATS Institute of Information Technology, Abbottabad 22060, Rau, A R. P., and Alber, G. Quantum discord for twoqubit X states. United States: N. p., 2010.
Web. doi:10.1103/PHYSREVA.81.042105.
Ali, Mazhar, Department of Electrical Engineering, COMSATS Institute of Information Technology, Abbottabad 22060, Rau, A R. P., & Alber, G. Quantum discord for twoqubit X states. United States. doi:10.1103/PHYSREVA.81.042105.
Ali, Mazhar, Department of Electrical Engineering, COMSATS Institute of Information Technology, Abbottabad 22060, Rau, A R. P., and Alber, G. Thu .
"Quantum discord for twoqubit X states". United States. doi:10.1103/PHYSREVA.81.042105.
@article{osti_21413321,
title = {Quantum discord for twoqubit X states},
author = {Ali, Mazhar and Department of Electrical Engineering, COMSATS Institute of Information Technology, Abbottabad 22060 and Rau, A R. P. and Alber, G},
abstractNote = {Quantum discord, a kind of quantum correlation, is defined as the difference between quantum mutual information and classical correlation in a bipartite system. In general, this correlation is different from entanglement, and quantum discord may be nonzero even for certain separable states. Even in the simple case of bipartite quantum systems, this different kind of quantum correlation has interesting and significant applications in quantum information processing. So far, quantum discord has been calculated explicitly only for a rather limited set of twoqubit quantum states and expressions for more general quantum states are not known. In this article, we derive explicit expressions for quantum discord for a larger class of twoqubit states, namely, a sevenparameter family of so called X states that have been of interest in a variety of contexts in the field. We also study the relation between quantum discord, classical correlation, and entanglement for a number of twoqubit states to demonstrate that they are independent measures of correlation with no simple relative ordering between them.},
doi = {10.1103/PHYSREVA.81.042105},
journal = {Physical Review. A},
issn = {10502947},
number = 4,
volume = 81,
place = {United States},
year = {2010},
month = {4}
}