We show that, in two-path optical interferometry, the measurement of photon number parity achieves maximal phase sensitivity at the quantum Cramér-Rao bound for a certain type of path-symmetric states. All pure states of light proposed for sub-shot-noise phase sensitivity thus far in the literature are of the form of these path-symmetric states. Thus, parity measurement presents an optimal detection strategy for all of them. Our scheme is applicable for local phase estimation. © 2013 American Physical Society.
Publication Source (Journal or Book title)
Physical Review A - Atomic, Molecular, and Optical Physics
Seshadreesan, K., Kim, S., Dowling, J., & Lee, H. (2013). Phase estimation at the quantum Cramér-Rao bound via parity detection. Physical Review A - Atomic, Molecular, and Optical Physics, 87 (4) https://doi.org/10.1103/PhysRevA.87.043833