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Open Access research that challenges the mind...

The Strathprints institutional repository is a digital archive of University of Strathclyde research outputs. Strathprints provides access to thousands of Open Access research papers by University of Strathclyde researchers, including those from the School of Psychological Sciences & Health - but also papers by researchers based within the Faculties of Science, Engineering, Humanities & Social Sciences, and from the Strathclyde Business School.

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Direct estimations of linear and nonlinear functionals of a quantum state

Ekert, A K and Alves, C M and Oi, D K L and Horodecki, M and Horodecki, P and Kwek, L C (2002) Direct estimations of linear and nonlinear functionals of a quantum state. Physical Review Letters, 88 (21). -. ISSN 0031-9007

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Abstract

We present a simple quantum network, based on the controlled-SWAP gate, that can extract certain properties of quantum states without recourse to quantum tomography. It can be used as a basic building block for direct quantum estimations of both linear and nonlinear functionals of any density operator. The network has many potential applications ranging from purity tests and eigenvalue estimations to direct characterization of some properties of quantum channels. Experimental realizations of the proposed network are within the reach of quantum technology that is currently being developed.