Practical limits for large-momentum-transfer clock atom interferometers

TL;DR

This paper investigates the fundamental laser noise constraints on large-momentum-transfer atom interferometers using optical clock transitions, highlighting the need for ultra-narrow linewidth lasers for high-fidelity measurements.

Contribution

It identifies the critical laser linewidth requirements for large-momentum transfer in atom interferometry and presents two stabilized laser sources for cadmium and strontium clock transitions.

Findings

Laser linewidth must be significantly narrower than previously thought for high-fidelity momentum transfer.

Imperfect pulse fidelity due to laser noise is a fundamental limit even at resonance.

Two high-power, frequency-stabilized lasers for cadmium and strontium are demonstrated.

Abstract

Atom interferometry on optical clock transitions is being pursued for numerous long-baseline experiments both terrestrially and for future space missions. Crucial to meeting these experiments' required sensitivities is the implementation of large momentum transfer ($>$10$^3\hbar k$). Here we show that to sequentially apply such a large momentum via $\pi$ pulses places stringent requirements on the frequency noise of the interferometry laser, finding that the linewidth is required to be considerably lower than has previously been suggested. This is due to imperfect pulse fidelity in the presence of noise and is apparent even for an atom at rest interacting with resonant light, making this a fundamental constraint on operational fidelity for a given laser and pulse sequence. Within this framework, we further present and analyse two high-power, frequency-stabilised laser sources designed to perform interferometry on the $^1$S$_0$ - $^3$P$_0$ clock transitions of cadmium and strontium, respectively operating at 332 nm and 698 nm.