Phase estimation without a priori knowledge in the presence of loss

Jan Kolodynski, Rafal Demkowicz-Dobrzanski

Published 2010-06-03, updated 2010-11-08Version 3

We find the optimal scheme for quantum phase estimation in the presence of loss when no a priori knowledge on the estimated phase is available. We prove analytically an explicit lower bound on estimation uncertainty, which shows that, as a function of number of probes, quantum precision enhancement amounts at most to a constant factor improvement over classical strategies