Enhancing the phase sensitivity of a Mach–Zehnder interferometer through dynamic squeezing

We develop squeezing sequences that enhance the phase sensitivity of a Mach–Zehnder interferometer independently of the input states that are injected into the interferometer. We show that by squeezing one mode of the interferometer along two orthogonal quadratures, a phase shift between the two arms of the Mach–Zehnder interferometer can generically be enhanced. Since the protocol is independent of the input states, the scheme allows for combining different quantum resources to improve the phase sensitivity beyond the standard quantum limit. In particular, we investigate how entangled input states that yield Heisenberg scaling can be combined with the developed squeezing sequences to trade between squeezing and entanglement to leverage the best from both resources. Finally, we study the impact of photon losses to identify the most efficient and robust squeezing strategies.