Linearly independent pure-state decomposition and quantum state discrimination

We put the pure-state decomposition mathematical property of a mixed state to a physical test. We begin by characterizing all the possible decompositions of a rank-two mixed state by means of the complex overlap between two involved states. The physical test proposes a scheme of quantum state recognition of one of the two linearly independent states which arise from the decomposition. We find that the two states associated with the balanced pure-state decomposition have the smaller overlap modulus and therefore the smallest probability of being discriminated conclusively, while in the nonconclusive scheme they have the highest probability of having an error. In addition, we design an experimental scheme which allows to discriminate conclusively and optimally two nonorthogonal states prepared with different a priori probabilities. Thus, we propose a physical implementation for this linearly independent pure-state decomposition and state discrimination test by using twin photons generated in the process of spontaneous parametric down conversion. The information-state is encoded in one photon polarization state whereas the second single-photon is used for heralded detection.Comment: 6 pages, 5 figures, Submitted to Phys. Rev.

A measure for maximum similarity between outcome states

We propose a measure to quantify correlations in a bipartite quantum system of two quibits by assessing the minimum difference between outcome states of a subsystem by performing a local measurement on the other subsystem. This maximum similarity measure is a monotone function of the concurrence for pure states of two qubits; for mixed states it accounts for entanglement, dissonance, and classical correlations. Besides, we found a closed formula for evaluating the similarity degree of an arbitrary mix state of two two-dimensional systems

A measure for maximum similarity between outcome states

We propose a measure to quantify correlations in a bipartite quantum system of two quibits by assessing the minimum difference between outcome states of a subsystem by performing a local measurement on the other subsystem. This maximum similarity measure is a monotone function of the concurrence for pure states of two qubits; for mixed states it accounts for entanglement, dissonance, and classical correlations. Besides, we found a closed formula for evaluating the similarity degree of an arbitrary mix state of two two-dimensional systems. © CopyrightEPLA, 2015

Erratum: A measure for maximum similarity between outcome states (EPL (2015) 109 (40001))

[No abstract available