Quantum discord for general two-qubit states: Analytical progress

By Davide Girolami, Gerardo Adesso. 2011

281 citations recorded by the source corpus.

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.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/ff8c5343deb3c86d6a0ca5fe4abf5c6896f72b70

How researchers see this paper

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In Artificial Intelligence

1. Kavan Modi
2. Tomasz Paterek
3. H. Cable
4. Aharon Brodutch
5. Vlatko Vedral

In Atomic and Molecular Physics, and Optics

1. Kavan Modi
2. Tomasz Paterek
3. H. Cable
4. Aharon Brodutch
5. Vlatko Vedral

Citations in the corpus

• The classical-quantum boundary for correlations: Discord and related measures (2011, background): “(Girolami and Adesso, 2011b) give another lower bound on geometric discord, in terms of the correlation tensor of a general bipartite state.”