Phase sensitivity for an unbalanced interferometer without input phase-matching restrictions

Abstract

The Cramér-Rao bound and the quantum Fisher information have been tools used extensively for interferometric phase sensitivity. Most scenarios considering a Mach-Zehnder interferometer with two input sources focused on the phase-matched case, when the Fisher information is maximal. Under this constraint, the best sensitivity is achieved for a balanced (50/50) input beam splitter. In this paper, we take a different approach: we allow the beam splitter transmission coefficient as well as the input phase mismatch to be variable parameters. We then search for a pair of these parameters that maximizes the Fisher information. We find that for the double coherent input the maximum Fisher information can always be reached in the unbalanced case for a carefully chosen input phase mismatch. For the coherent plus squeezed vacuum case we find that under certain circumstances a threshold phase mismatch exists, beyond which the optimum Fisher information is found for the degenerate case. For the squeezed-coherent plus squeezed vacuum case we find that the optimum actually occurs when the squeezing angles of the two inputs are in anti-phase.

11 pages, 7 figures

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Cited by in corpus (6)

• Single- versus two-parameter Fisher information in quantum interferometry
• Optimal Mach-Zehnder phase sensitivity with Gaussian states
• Quantum Fisher information maximization in an unbalanced interferometer
• Optimal phase sensitivity of an unbalanced Mach-Zehnder interferometer
• Enhancing phase sensitivity in Mach-Zehnder interferometer with various detection schemes using SU(1,1) coherent states
• Double-port measurements for robust quantum optical metrology