Squeezed matter-wave interferometer with direct phase resolution below the standard quantum limit

Collective cavity-QED systems with laser-cooled atoms in optical cavity have succeeded in generating large amounts of entanglement involving the internal degrees of freedom. In this talk, I will introduce the realization of cavity-QED entanglement of atomic external degrees of freedom to realize a matter-wave interferometer of 700 atoms in which each individual atom experiences free-falling and simultaneously traverses two paths through space while also entangled with the other atoms. We demonstrate both quantum non-demolition measurements and cavity-mediated interactions for generating squeezed momentum states with directly observed metrological gain 3.4^{+1.1}_{-0.9} dB and 2.5^{+0.6}_{−0.6} dB below the standard quantum limit respectively. An squeezed state is for the first time successfully injected into a Mach-Zehnder matter-wave interferometer with 1.7^{+0.5}_{−0.5} dB of directly observed metrological enhancement [1]. If time permits, I will also introdue our recent result on realizing a momentum exchange interaction in the same system, where atoms exchange their momentum states through interacting with a common cavity mode. We observe both one-axis twisting dynamics and many-body energy gap arising from this momentum exchange interaction, which may provide a new platform for quantum simulation as well as improve precision measurements.

[1] G. P. Greve*, C. Luo*, B. Wu, and J. K. Thompson, Nature 610, 472 (2022).