Phys. Rev. A 70, 032310 (2004) [6 pages]Entanglement is not very useful for estimating multiple phasesReceived 8 April 2004; published 13 September 2004 The problem of the estimation of multiple phases (or of commuting unitaries) is considered. This is a submodel of the estimation of a completely unknown unitary operation where it has been shown in recent works that there are considerable improvements by using entangled input states and entangled measurements. Here it is shown that, when estimating commuting unitaries, there is practically no advantage in using entangled input states or entangled measurements. © 2004 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevA.70.032310
DOI:
10.1103/PhysRevA.70.032310
PACS:
03.67.Mn
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