Phase super-resolution using a photonic crystal fibre

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 √n on a phase shift Δφ 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 (|N0〉_A;B +|0N〉_A;B)/√2, where N is the number of entangled photons are of particular importance as they have repeatedly been shown to exhibit phase super-resolution. Interesting post selection schemes and time-reversed detection schemes have been investigated for phase estimation using NOON states. These methods are inherently non-deterministic at the preparation or measurement stage and thus do not optimise resources, for instance the number of photons passing through the sample greatly exceeds those used in the measurement.