Improvement of phase sensitivity in an SU(1,1) interferometer via a phase shift induced by a Kerr medium

We theoretically study the phase sensitivity of an SU(1,1) interferometer, in which the phase shift is induced by a Kerr medium, together with a coherent state input and homodyne detection. Considering both ideal and photon-loss cases, the results show that compared with the linear-phase-shift-based SU(1,1) interferometer, the Kerr-phase-shift-based SU(1,1) [KSU(1,1)] interferometer can show the significant enhancement of the phase sensitivity and quantum Fisher information even in the presence of photon losses. In particular, without photon losses, the phase sensitivity of the KSU(1,1) interferometer can break through the standard quantum limit and the Heisenberg limit (HL), even close to the super-HL. From the perspective of quantum resource theory, it is interesting that the phase shift induced by the Kerr medium shows an obvious advantage of low-cost input resources to obtain higher phase sensitivity and larger quantum Fisher information. These findings may have potential applications for state-of-the-art quantum information technology.