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Achieving the uncertainty limit of phase estimation in two-path interferometers

Holger Friedrich Hofmann

Published Aug 1, 2009• 1 citation
Publisher

Abstract

The optimal phase estimation based on output photon number statistics of two-path interferometers is discussed. It is shown that for many pure states, conventional photon detection is sufficient to achieve the uncertainty limit.
DOI
10.1109/cleopr.2009.5292062

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We study a Mach-Zehnder interferometer fed by a coherent state in one input port and vacuum in the other. We explore a Bayesian phase estimation strategy to demonstrate that it is possible to achieve the standard quantum limit independently from the true value of the phase shift and specific assumptions on the noise of the interferometer. We have been able to implement the protocol by using parallel operation of two photon-number-resolving detectors and multiphoton coincidence logic electronics at the output ports of a weakly illuminated Mach-Zehnder interferometer. This protocol is unbiased, saturates the Cramer-Rao phase uncertainty bound, and, therefore, is an optimal phase estimation strategy.
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