Entanglement-Enhanced Matter-Wave Interferometer

Collective cavity-QED systems have succeeded in generating large amounts (as much as 18.5 dB) [1,2] of directly observed entanglement beyond the standard quantum limit (SQL), which sets a fundamental limit on phase resolution for all quantum sensors with unentangled atoms. Here, we demonstrate for the first time a matter-wave interferometer with 1.7(5)dB directly observed metrological enhancement of phase resolution beyond the SQL [3]. With the atoms free-falling inside a high-finesse cavity, the entanglements of the external degrees of freedom are generated through both quantum non-demolition measurements and cavity-mediated spin interactions, with directly observed metrological gain 3.4(1.0)dB and 2.5(6)dB below the SQL respectively. These results open a new path for combining particle delocalization to directly enhance measurement precision, bandwidth, and accuracy or to operate at reduced size.

[1] K.C. Cox, G.P. Greve, J.M. Weiner, J.K. Thompson. PRL 116 093602  (2016)

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

[3] G. P. Greve*, C. Luo*, B. Wu, J.K. Thompson. arXiv:2110.14027 (2021).