Comparison of unitary transforms using Franson interferometry |
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Authors: | Erika Andersson Janos Bergou Igor Jex |
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Affiliation: | 1. Department of Physics , University of Strathclyde , Glasgow G4 0NG, UK;2. Department of Physics and Astronomy , Hunter College of The City University of New York , 695 Park Avenue, New York, NY 10021, USA;3. Department of Physics , FNSPE Czech Technical University in Prague B?ehová 7 , 115 19 Praha 1, Czech Republic |
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Abstract: | Unknown unitary transforms may be compared to each other in a way which makes it possible to obtain an unambiguous answer, indicating that the transforms are different, already after a single application of each transform. Quantum comparison strategies may be useful for example if we want to test the performance of individual gates in a quantum information or quantum computing network. It is then possible to check for errors by comparing the elements to a master copy of the gate, instead of performing a complete tomography of the gate. In this paper we propose a versatile linear optical implementation based on the Franson interferometer with short and long arms. A click in the wrong output port unambiguously determines that the tested gate is faulty. This set-up can also be used for a variety of other tasks, such as confirming that the two transforms do not commute or do not anticommute. |
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