In this letter, we show that for all the so-called path-symmetric states, the measurement of parity of photon number at the output of an optical interferometer achieves maximal phase sensitivity at the quantum Cramer-Rao bound. Such optimal phase sensitivity with parity is attained at a suitable bias phase, which can be determined a priori. Our scheme is applicable for local phase estimation.
@article{arxiv.1207.0494,
title = {Parity Measurement is Sufficient for Phase Estimation at the Quantum Cramer-Rao Bound for Path-Symmetric States},
author = {Sejong Kim and Kaushik P. Seshadreesan and Jonathan P. Dowling and Hwang Lee},
journal= {arXiv preprint arXiv:1207.0494},
year = {2015}
}