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Orthogonal measurements are almost sufficient for quantum discord of two qubits

AuthorsGalve, Fernando ; Giorgi, Gian Luca ; Zambrini, Roberta
Issue Date2011
PublisherEDP Sciences
CitationEurophysics Letters 96, 40005 (2011)
AbstractThe common use in literature of orthogonal measurements in obtaining quantum discord for two-qubit states is discussed and compared with more general measurements. We prove the optimality of orthogonal measurements for rank 2 states. While for rank 3 and 4 mixed states they are not optimal, we present strong numerical evidence showing that they give the correct quantum discord up to minimal corrections. Based on the connection, through purification with an ancilla, between discord and entanglement of formation (EoF), we give a tight upper bound for the EoF of a $2otimes N$ mixed state of rank 2, given by an optimal decomposition of 2 elements. We also provide an alternative way to compute the quantum discord for two qubits based on the Bloch vectors of the state.
DescriptionTexto completo ArXiv: Number 1107.2005. -- PACS 03.67.Mn – Entanglement measures, witnesses, and other characterizations PACS 03.65.Ta – Foundations of quantum mechanics; measurement theory PACS 03.65.Ud – Entanglement and quantum nonlocality
Publisher version (URL)http://dx.doi.org/10.1209/0295-5075/96/40005
Appears in Collections:(IFISC) Artículos
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