Quantum discord for general two-qubit states: Analytical progress
- 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
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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