The phase sensitivity of a lossy truncated SU(1,1) interferometer with double-port homodyne detection

In this paper, we theoretically investigate the phase sensitivity in a truncated SU(1,1) interferometer with a two-mode coherent state and the double-port homodyne detection. On the one hand, we analytically demonstrate that the two-mode coherent state can provide better phase sensitivity than the single-mode coherent state. In addition, we show that the double-port homodyne detection is a quasi-optimal measurement. For a bright coherent state input, the sensitivity of this scheme saturates the phase sensitivity bound determined by the quantum Fisher information. On the other hand, we quantitatively illustrate the advantage of the double-port homodyne detection over the single-port scheme in the ideal scenarios and in the presence of photon loss, respectively. Furthermore, our analysis also indicates that the scheme we propose is robust against the photon loss.