0005132v2

related topics
{states, state, optimal}
{let, theorem, proof}
{measurement, state, measurements}
{error, code, errors}
{information, entropy, channel}
{group, space, representation}
{alice, bob, state}
{photon, photons, single}
{vol, operators, histories}

On Quantum Detection and the Square-Root Measurement

Yonina C. Eldar, G. David Forney

abstract: In this paper we consider the problem of constructing measurements optimized to distinguish between a collection of possibly non-orthogonal quantum states. We consider a collection of pure states and seek a positive operator-valued measure (POVM) consisting of rank-one operators with measurement vectors closest in squared norm to the given states. We compare our results to previous measurements suggested by Peres and Wootters [Phys. Rev. Lett. 66, 1119 (1991)] and Hausladen et al. [Phys. Rev. A 54, 1869 (1996)], where we refer to the latter as the square-root measurement (SRM). We obtain a new characterization of the SRM, and prove that it is optimal in a least-squares sense. In addition, we show that for a geometrically uniform state set the SRM minimizes the probability of a detection error. This generalizes a similar result of Ban et al. [Int. J. Theor. Phys. 36, 1269 (1997)].

oai_identifier:
oai:arXiv.org:quant-ph/0005132
categories:
quant-ph
comments:
Version of August 29, 2000, with minor revisions. To appear in the IEEE Transactions on Information Theory. RevTex, 48 pages, 3 figures. A briefer version of this paper has also been submitted to Physical Review Letters. A copy is obtainable by writing to the authors at yonina@mit.edu
arxiv_id:
quant-ph/0005132
journal_ref:
IEEE Trans. Inform. Theory, vol. 47, pp. 858-872, Mar. 2001
created:
2000-05-31
updated:
2000-08-29

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