Long-baseline atom interferometers offer a promising approach for gravitational wave detection and dark matter searches, motivating large-scale initiatives such as AION [1], MAGIS [2] and AICE [3]. While most common atom interferometers use two-photon interactions, the sensitivity requirements of these applications benefit from a gradiometer configuration using a single-photon, narrow-line clock transition. The long-lived excited state of an optical clock transition enables long interrogation time with negligible spontaneous emission losses, while the differential configuration on a single-photon transition allows for strong suppression of laser phase noise.
Large Momentum Transfer (LMT) techniques use additional light pulses to increase the momentum separation between the two interferometer arms, leading to enhanced sensitivity. The realisation of LMT-enhanced atom interferometry on a single photon clock transition is therefore a crucial milestone towards long-baseline interferometers.
The AION project has recently built a gradiometer using the single-photon 1S0 - 3P0 clock transition of 87Sr, demonstrating laser phase noise rejection and operation at the standard quantum limit [4]. We have then implemented LMT-enhanced interferometry in a Mach-Zehnder, differential configuration, reaching a momentum separation of 71 ℏk between the interferometer arms. I will present in this talk the experimental steps we took for this demonstration.
[1] L. Badurina et al., AION: an atom interferometer observatory and network, Journal of Cosmology and Astroparticle Physics (2020)
[2] M. Abe et al., Matter-wave Atomic Gradiometer Interferometric Sensor (MAGIS-100), Quantum Sci. Technolog. 6.
[3] C. F. A. Baynham et al., Letter of Intent: AICE - Atom Interferometry CERN Experiment, Letter of Intent submitted to CERN, LHCC (2025)
[4] C. F. A. Baynham et al., A prototype differential atom interferometer for fundamental physics, Nature 654.8119 (2026)