A Michelson interferometer-based LIDAR scheme: Super-sensitivity in the presence of noise and loss

Quantum Light Detection and Ranging (quantum-LIDAR) schemes show super-resolution and super-sensitivity (beating the Rayleigh and shot noise limits). This is achieved using non-classical sources like squeezed light and quantum detection apparatus such as single photon detectors. Here, we optimize the phase sensitivity of a Michelson interferometer-based LIDAR scheme under lossy and noisy conditions. We consider an entangled source in the form of a two-mode squeezed coherent state (TMSCS), which offers significant (exponential) quantum advantage for phase sensitivity over classical coherent sources. We find the maximum possible loss and thermal noise levels under which the shot noise limit can still be broken, maintaining the quantum advantage. We show that by solely controlling the squeezing angle and without changing the input power the sensitivity can be improved. This accommodates larger losses (up to 80%) than the zero-squeezing-angle case which was considered optimal prior to this work. We also compare the above optimization scheme to other possible methods like using input beams of different strengths or beam splitters with different transmissivities for input and output. Finally, we compare the noise and loss robustness of TMSCS against other entangled states as sources.