Eur. Phys. J. D (2012) 66: 185
https://doi.org/10.1140/epjd/e2012-20618-3

Regular Article

Programmed discrimination of multiple sets of qbits with added classical information¹

Department of Physics, Scottish Universities Physics Alliance, Strathclyde University, John Anderson Building, 107 Rottenrow, G4 0 NG Glasgow, UK

^a e-mail: andrew@crm.scotnet.co.uk

Received: 25 October 2011
Received in final form: 31 January 2012
Published online: 20 July 2012

Abstract

This paper offers some new results in the area of programmed quantum discrimination, which determines whether a data qbit is the same as the first or second of a given pair of program qbits. In a recent paper [A.J.T. Colin, S.M. Barnett, J. Jeffers, Eur. Phys. J. D 63, 463 (2011)] we examined the effect of additional classical information on this process. We now extend our work to consider the effects of replicating some or all of the qbits in the group. As the parameters to the calculations can take many values in several dimensions, we offer only a sample of results. A suite of programs [A.J.T. Colin, Multiple qbit discrimination programs, www.phys.strath.ac.uk/cnqo/?page_id=450] allows the reader to explore the problem space in detail. Turning to a possible application of the method, we investigate the efficacy of programmed discrimination in the context of data communication. The technique offers a key advantage over other methods of quantum-based data transmission; namely, that it is insensitive to any unitary transformation that may occur in transit, provided only that the same transformation applies equally to all the qbits in the group. However, the technique is costly in its use of resources. Using the best configuration we could find, with unambiguous discrimination, orthogonal program qbits, and a duplicated data qbit, the transmission of one binary digit reliably still needs 8 qbits.