Differential interferometry works also with quantum entangled states


Differential interferometry (DI) with two coupled sensors is a most powerful approach for precision measurements in the presence of strong phase noise. However, DI has been studied and implemented only with classical resources. Here we generalize the theory of differential interferometry to the case of entangled probe states. We demonstrate that, for perfectly correlated interferometers and in the presence of arbitrary large phase noise, sub-shot noise sensitivities — up to the Heisenberg limit — are still possible with a special class of entangled states in the ideal lossless scenario.

M. Landini et al.,
Phase-noise protection in quantum-enhanced differential interferometry
New J. Phys. 16, 113074 (2014)