Free Space Ramsey Spectroscopy in Rubidium with Noise below the Quantum Projection Limit

Benjamin K. Malia, Julián Martínez-Rincón, Yunfan Wu, Onur Hosten, and Mark A. Kasevich
Phys. Rev. Lett. 125, 043202 – Published 24 July 2020
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Abstract

We demonstrate the utility of optical cavity generated spin-squeezed states in free space atomic fountain clocks in ensembles of 390 000 Rb87 atoms. Fluorescence imaging, correlated to an initial quantum nondemolition measurement, is used for population spectroscopy after the atoms are released from a confining lattice. For a free fall time of 4 milliseconds, we resolve a single-shot phase sensitivity of 814(61) microradians, which is 5.8(0.6) decibels (dB) below the quantum projection limit. We observe that this squeezing is preserved as the cloud expands to a roughly 200μm radius and falls roughly 300μm in free space. Ramsey spectroscopy with 240 000 atoms at a 3.6 ms Ramsey time results in a single-shot fractional frequency stability of 8.4(0.2)×1012, 3.8(0.2) dB below the quantum projection limit. The sensitivity and stability are limited by the technical noise in the fluorescence detection protocol and the microwave system, respectively.

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  • Received 21 December 2019
  • Accepted 15 June 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.043202

© 2020 American Physical Society

Physics Subject Headings (PhySH)

Quantum Information, Science & TechnologyAtomic, Molecular & Optical

Authors & Affiliations

Benjamin K. Malia1, Julián Martínez-Rincón1, Yunfan Wu2, Onur Hosten3, and Mark A. Kasevich1,2,*

  • 1Department of Physics, Stanford University, Stanford, California 94305, USA
  • 2Department of Applied Physics, Stanford University, Stanford, California 94305, USA
  • 3Institute of Science and Technology Austria, Klosterneuburg 3400, Austria

  • *kasevich@stanford.edu

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Issue

Vol. 125, Iss. 4 — 24 July 2020

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