Improved resolution and sensitivity of angular rotation measurement using entangled coherent states

The performance of entangled coherent states for super-resolving angular-rotation measurement is investigated in this paper. Entangled coherent states with nonzero orbital angular momentum are first used as the input state, and parity detection method is adopted for signal processing. Analytical expressions of the output signal are derived. Numerical results show that the resolution and sensitivity of angular-rotation measurement using entangled coherent states are further enhanced relatively to those using classical coherent states. Moreover, this paper gives a detailed discussion about the impact of photon loss on the resolution and sensitivity of angular-rotation measurement.