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Quantum Physics

arXiv:1103.3189 (quant-ph)
[Submitted on 16 Mar 2011 (v1), last revised 19 May 2011 (this version, v2)]

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

Authors:Davide Girolami, Gerardo Adesso
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Abstract: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 non-classical correlations, namely the geometric discord. We identify the extremally non-classically correlated two--qubit states according to the (normalized) geometric discord, at fixed value of the conventional quantum discord. The latter cannot exceed the square root of the former for systems of two qubits.
Comments: 8 pages, 2 figures
Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph)
Cite as: arXiv:1103.3189 [quant-ph]
  (or arXiv:1103.3189v2 [quant-ph] for this version)
  https://doi.org/10.48550/arXiv.1103.3189
Journal reference: Phys. Rev. A 83, 052108 (2011)
Related DOI: https://doi.org/10.1103/PhysRevA.83.052108

Submission history

From: Gerardo Adesso [view email]
[v1] Wed, 16 Mar 2011 15:00:57 UTC (397 KB)
[v2] Thu, 19 May 2011 23:53:45 UTC (397 KB)
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