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Robust sub-shot-noise measurement via Rabi-Josephson oscillations in bimodal Bose-Einstein condensates

Mach-Zehnder atom interferometry requires hold-time phase-squeezing to attain readout accuracy below the standard quantum limit. This increases its sensitivity to phase-diffusion, restoring shot-noise scaling of the optimal signal-to-noise ratio, $s_o$, in the presence of interactions. The contradiction between the preparations required for readout accuracy and robustness to interactions, is removed by monitoring Rabi-Josephson oscillations instead of relative-phase oscillations during signal acquisition. Optimizing $s_o$ with a Gaussian squeezed input, we find that hold-time number squeezing satisfies both demands and that sub-shot-noise scaling is retained even for strong interactions.