arXiv:quant-ph/0305104AbstractReferencesReviewsResources
Estimation of unitary quantum operations
Published 2003-05-19, updated 2004-05-02Version 3
The problem of optimally estimating an unknown unitary quantum operation with the aid of entanglement is addressed. The idea is to prepare an entangled pair, apply the unknown unitary to one of the two parts and then measure the joint output state. This measurement could be an entangled one or it could be separable (e.g., LOCC). A comparison is made between these possibilities and it is shown that by using non-separable measurements one can improve the accuracy of the estimation by a factor of $2(d+1)/d$ where $d$ is the dimension of the Hilbert space on which $U$ acts.
Comments: 6 pages. Revised version. Typos corrected. Some discussion added. Reference fixed
Journal: Phys. Rev. A 69, 022303 (2004)
Categories: quant-ph
Keywords: estimation, unknown unitary quantum operation, joint output state, measurement, hilbert space
Tags: journal article
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