Unambiguous comparison of unitary channels
arXiv:0809.4401 · doi:10.1103/PhysRevA.79.012303
Abstract
We address the problem of unambiguous comparison of a pair of unknown qudit unitary channels. Using the framework of process positive operator valued measures (PPOVM) we characterize all solutions and identify the optimal ones. We prove that the entanglement is the key ingredient in designing the optimal experiment for comparison of unitary channels. Without entanglement the optimality can not be achieved. The proposed scheme is also experimentally feasible.
Version published in PRA, 7 pages, 1 figure
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- Optimal quantum discrimination of single-qubit unitary gates between two candidates
- Discrimination and certification of unknown quantum measurements