Asymmetry-enhanced phase sensing via asymmetric entangled coherent states

We study quantum phase sensing with an asymmetric two-mode entangled coherent state (ECS) in which the two local amplitudes have different values. We find the phenomenon of the asymmetry-enhanced phase sensing which the asymmetry can significantly increase the precise of the phase estimation. We further study the effect of decoherence induced by the photon loss on quantum phase sensing. It is shown that the asymmetric ECSs have stronger capability against decoherence over the symmetric ECSs. It is indicated that the asymmetric ECSs have obvious advantages over the symmetric ECSs in the quantum phase sensing. We also study the practical phase sensing scheme with the intensity-difference measurement, and show that the asymmetry in the asymmetric ECSs can enhance the phase sensitivity in the practical phase measurement scheme. Our work reveals the asymmetry in the asymmetric ECSs is a new quantum-sensing resource, and opens a new way to the ultra-sensitive quantum phase sensing in the presence of photon losses.