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Decision problems with quantum black boxes

Hillery, Mark and Andersson, Erika and Barnett, Stephen M. and Oi, Daniel (2010) Decision problems with quantum black boxes. Journal of Modern Optics, 57 (3). pp. 244-252. ISSN 0950-0340

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Abstract

We examine how to distinguish between unitary operators, when the exact form of the possible operators is not known. Instead we are supplied with 'programs' in the form of unitary transforms, which can be used as references for identifying the unknown unitary transform. All unitary transforms should be used as few times as possible. This situation is analogous to programmable state discrimination. One difference, however, is that the quantum state to which we apply the unitary transforms may be entangled, leading to a richer variety of possible strategies. By suitable selection of an input state and generalized measurement of the output state, both unambiguous and minimum-error discrimination can be achieved. Pairwise comparison of operators, comparing each transform to be identified with a program transform, is often a useful strategy. There are, however, situations in which more complicated strategies perform better. This is the case especially when the number of allowed applications of program operations is different from the number of the transforms to be identified.

Item type: Article
ID code: 26647
Keywords: unambiguous discrimination, optimum discrimination, operator comparison, generalized measurements, fibre optics, optoelectronics, optics, optoelectronic effects, devices & systems, Optics. Light, Atomic and Molecular Physics, and Optics
Subjects: Science > Physics > Optics. Light
Department: Faculty of Science > Physics
Depositing user: Miss Leonie Airley
Date Deposited: 10 Aug 2010 09:37
Last modified: 26 Mar 2015 20:50
URI: http://strathprints.strath.ac.uk/id/eprint/26647

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