Picture of athlete cycling

Open Access research with a real impact on health...

The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by Strathclyde researchers, including by researchers from the Physical Activity for Health Group based within the School of Psychological Sciences & Health. Research here seeks to better understand how and why physical activity improves health, gain a better understanding of the amount, intensity, and type of physical activity needed for health benefits, and evaluate the effect of interventions to promote physical activity.

Explore open research content by Physical Activity for Health...

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

[img]
Preview
PDF
operatordecisionJModOptArxiv.pdf - Accepted Author Manuscript

Download (219kB) | Preview

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.