2026/07/30 by Asad Ali, Saif Al-Kuwari
Physics and Astronomy · #quant-ph
arxiv created 2026/07/30 · arxiv updated 2026/08/03
Large momentum transfer (LMT) enhances the gravitational phase of a light-pulse atom interferometer by a factor n, while mirrorless operation with momentum-resolved detection can quadruple the phase-carrying quantum Fisher information. These gains compete in practice because the momentum-space fringe period scales as 1/n, making the fringe signal increasingly vulnerable to finite detector resolution. We analyze this trade-off in a solvable model with instantaneous lossless n-photon pulses, a Gaussian source, and Gaussian detection blur, allowing continuous interpolation between Kasevich--Chu and mirrorless geometries. Closed-form expressions for the blurred output distributions and classical Fisher information are obtained, with a fringe-phase averaging approximation whose error is exponentially suppressed and agrees with numerical simulations at the 10-8 level. We find that mirrorless operation surpasses a conventional interferometer with the same momentum transfer only when σp < 0.91 m/(n k0 T). Fringe-based readout exhibits an optimal momentum transfer n^* ≃ 0.93 m/(σp k0 T) and a resolution-limited sensitivity floor Δg ≃ 4.4 σp/(mT√(N)), independent of photon momentum. When this criterion is not satisfied, partial mirror asymmetry can recover part of the enhancement, whereas population-based readout remains insensitive to detector blur and ultimately favors the conventional sequence at sufficiently large n. Estimates for 87Rb sensors show that the mirrorless advantage is primarily restricted to short-baseline instruments.