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arXiv:quant-ph/0606156 · New Journal of Physics

Optimal probabilistic estimation of quantum states

Jaromı́r Fiurášek

Published Sep 14, 2006• 22 citations
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Abstract

We extend the concept of probabilistic unambiguous discrimination of quantum states to quantum state estimation. We consider a scenario where the measurement device can output either an estimate of the unknown input state or an inconclusive result. We present a general method how to evaluate the maximum fidelity achievable by the probabilistic estimation strategy. We illustrate our method on two explicit examples: estimation of a qudit from a pair of conjugate qudits and phase covariant estimation of a qubit from N copies. We show that by allowing for inconclusive results it is possible to reach estimation fidelity higher than that achievable by the best deterministic estimation strategy.

DOI
10.1088/1367-2630/8/9/192

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