Quantum optical metrology in the lossy SU(2) and SU(1,1) interferometers

摘要

We study the phase sensitivity in the conventional SU(2) and nonconventional SU(1,1) interferometers with a coherent and squeezed vacuum input state via quantum Cramer-Rao bound.We explicitly construct the detection scheme that gives the optimal phase sensitivity. For practical purposes, we show that in the presence of photon loss, both interferometers with proper homodyne detections are nearly optimal. We also find that unlike the coherent state and the squeezed vacuum state, the effects of imperfect detector on the phase sensitivity cannot be asymptotically removed for a generic coherent-squeezed state.