Towards a squeezed Mach-Zehnder-type atom interferometer in an optical, propagating-wave cavity

The sensitivity of atom interferometric sensors can be increased beyond the standard quantum limit by utilizing entangled states of the utilized atomic ensemble. Spin-squeezed states, a particularly useful set of entangled states, have shown metrological enhancement levels up to 20 dB [1], and have been implemented in atomic clock protocols [2]. There are now ongoing efforts to apply the same principles to inertia-sensitive atom interferometers [3].

We will report on the progress of our experiment for developing a squeezed Mach-Zehnder-type atom interferometer in an optical propagating-wave cavity, where initial quantum correlations between internal atomic degrees of freedom are mapped onto spatially separated interferometer arms. The cavity traps the atoms during the whole sequence and it supports the Raman-transition based spin-to-momentum mapping enabled by counter-propagating intra-cavity tones. Cavity-enhanced atom-light couplings entangle the atoms via the one-axis twisting interaction and projective quantum measurements. We demonstrate protocols for squeezed state generation and we discuss AC-stark shift compensation by a weak, blue-detuned auxiliary potential.

[1] O. Hosten, N. Engelsen, R. Krishnakumar, M. Kasevich, Nature 529, 505 (2016).

[2] E. Pedrozo-Penafiel et al., Nature 588, 414 (2020).

[3] C. Cassens, B. Meyer-Hoppe, E. Rasel, and C. Klempt. arXiv:2404.18668 (2024).