Quantum discord for general two-qubit states: Analytical progress

Journal Article · Sun May 15 00:00:00 EDT 2011 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.83.052108· OSTI ID:21546697

Girolami, Davide; Adesso, Gerardo ^[1]

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1. School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

We present a reliable algorithm to evaluate quantum discord for general two-qubit states, amending and extending an approach recently put forward for the subclass of X states. A closed expression for the discord of arbitrary states of two qubits cannot be obtained, as the optimization problem for the conditional entropy requires the solution to a pair of transcendental equations in the state parameters. We apply our algorithm to run a numerical comparison between quantum discord and an alternative, computable measure of nonclassical correlations, namely, the geometric discord. We identify the extremally nonclassically correlated two-qubit states according to the (normalized) geometric discord, at a fixed value of the conventional quantum discord. The latter cannot exceed the square root of the former for systems of two qubits.

• OSTI ID: 21546697
• Journal Information: Physical Review. A, Vol. 83, Issue 5; Other Information: DOI: 10.1103/PhysRevA.83.052108; (c) 2011 American Institute of Physics; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALGORITHMS
ANALYTIC FUNCTIONS
COMPARATIVE EVALUATIONS
CORRELATIONS
ENTROPY
GEOMETRY
MATHEMATICAL SOLUTIONS
OPTIMIZATION
QUANTUM STATES
QUBITS
TWO-BODY PROBLEM
EVALUATION
FUNCTIONS
INFORMATION
MANY-BODY PROBLEM
MATHEMATICAL LOGIC
MATHEMATICS
PHYSICAL PROPERTIES
QUANTUM INFORMATION
THERMODYNAMIC PROPERTIES