Abstract

Measurement, whilst being physically fundamental, is also fundamentally physical. Classical interferometric measurements suffer from physical limitations where the shot noise limit forms an upper bound of $\sqrt{n}$ on a phase shift ∆ϕ that can be resolved, with n being the average number of photons detected, making their applicability in modern nanoscale experiments quite restricted. Exotic quantum states such as maximally entangled NOON states $\left(\left|{N0〉}_{A,B}+\right|{0N〉}_{A,B}\right)/\sqrt{2}$, where N is the number of entangled photons are of particular importance as they have repeatedly been shown to exhibit phase super-resolution [1,2]. Interesting post selection schemes [2] and time-reversed detection schemes [3] have been investigated for phase estimation using NOON states. These methods are inherently non-deterministic at the preparation [2] or measurement [3] stage and thus do not optimise resources, for instance the number of photons passing through the sample greatly exceeds those used in the measurement.

© 2011 IEEE