Balancing Quasi-Bragg Regime and Velocity Selectivity in Quantum-Enhanced Atom Interferometry

TL;DR

This paper analyzes the trade-offs in atom interferometry between Bragg diffraction regimes and velocity selectivity, deriving analytical models to optimize quantum-enhanced sensitivity.

Contribution

It introduces analytical expressions for phase uncertainty considering competing diffraction effects, identifying optimal pulse durations for sub-shot-noise performance.

Findings

Sub-shot-noise scaling occurs at intermediate pulse durations.

Higher-order diffraction effects can be mitigated by input quantum state optimization.

Analytical models guide the balance between diffraction regimes and velocity selectivity.

Abstract

Spin squeezing in atomic ensembles enables atom interferometry with sensitivities below the shot-noise limit, but the associated entanglement is highly susceptible to loss, making imperfections in atom optics a central limitation. Bragg diffraction is an established technique for driving transitions between atomic momentum states and enables large-momentum transfer through higher-order diffraction while preserving the internal state. However, it is intrinsically limited by two competing mechanisms: short light pulses induce parasitic diffraction into off-resonant orders beyond an effective two-level description, while long pulses face velocity selectivity. We derive analytical expressions in a second-quantized framework for the atom optics and phase uncertainty of a Mach-Zehnder interferometer including these effects. We demonstrate that sub-shot-noise scaling is achieved only in a regime of intermediate pulse duration. Furthermore, we show that deleterious effects of higher-order diffraction are partially mitigated by optimizing the input quantum state.