{"department":[{"_id":"OnHo"}],"date_published":"2020-07-24T00:00:00Z","oa_version":"Preprint","oa":1,"abstract":[{"lang":"eng","text":"We demonstrate the utility of optical cavity generated spin-squeezed states in free space atomic fountain clocks in ensembles of 390 000 87Rb 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 200  μm radius and falls roughly 300  μm 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)×10−12, 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."}],"pmid":1,"type":"journal_article","article_type":"original","publisher":"American Physical Society","article_number":"043202","day":"24","issue":"4","intvolume":"       125","date_created":"2020-08-24T06:24:04Z","language":[{"iso":"eng"}],"publication_identifier":{"issn":["0031-9007"],"eissn":["1079-7114"]},"article_processing_charge":"No","title":"Free space Ramsey spectroscopy in rubidium with noise below the quantum projection limit","acknowledgement":"This work is supported by the Office of Naval Research (N00014-16-1-2927- A00003), Vannevar Bush Faculty Fellowship (N00014-16-1-2812- P00005), Department of Energy (DE-SC0019174- 0001), and Defense Threat Reduction Agency (HDTRA1-15-1-0017- P00005).","status":"public","publication_status":"published","isi":1,"month":"07","publication":"Physical Review Letters","citation":{"mla":"Malia, Benjamin K., et al. “Free Space Ramsey Spectroscopy in Rubidium with Noise below the Quantum Projection Limit.” <i>Physical Review Letters</i>, vol. 125, no. 4, 043202, American Physical Society, 2020, doi:<a href=\"https://doi.org/10.1103/PhysRevLett.125.043202\">10.1103/PhysRevLett.125.043202</a>.","ista":"Malia BK, Martínez-Rincón J, Wu Y, Hosten O, Kasevich MA. 2020. Free space Ramsey spectroscopy in rubidium with noise below the quantum projection limit. Physical Review Letters. 125(4), 043202.","short":"B.K. Malia, J. Martínez-Rincón, Y. Wu, O. Hosten, M.A. Kasevich, Physical Review Letters 125 (2020).","ieee":"B. K. Malia, J. Martínez-Rincón, Y. Wu, O. Hosten, and M. A. Kasevich, “Free space Ramsey spectroscopy in rubidium with noise below the quantum projection limit,” <i>Physical Review Letters</i>, vol. 125, no. 4. American Physical Society, 2020.","chicago":"Malia, Benjamin K., Julián Martínez-Rincón, Yunfan Wu, Onur Hosten, and Mark A. Kasevich. “Free Space Ramsey Spectroscopy in Rubidium with Noise below the Quantum Projection Limit.” <i>Physical Review Letters</i>. American Physical Society, 2020. <a href=\"https://doi.org/10.1103/PhysRevLett.125.043202\">https://doi.org/10.1103/PhysRevLett.125.043202</a>.","ama":"Malia BK, Martínez-Rincón J, Wu Y, Hosten O, Kasevich MA. Free space Ramsey spectroscopy in rubidium with noise below the quantum projection limit. <i>Physical Review Letters</i>. 2020;125(4). doi:<a href=\"https://doi.org/10.1103/PhysRevLett.125.043202\">10.1103/PhysRevLett.125.043202</a>","apa":"Malia, B. K., Martínez-Rincón, J., Wu, Y., Hosten, O., &#38; Kasevich, M. A. (2020). Free space Ramsey spectroscopy in rubidium with noise below the quantum projection limit. <i>Physical Review Letters</i>. American Physical Society. <a href=\"https://doi.org/10.1103/PhysRevLett.125.043202\">https://doi.org/10.1103/PhysRevLett.125.043202</a>"},"volume":125,"scopus_import":"1","main_file_link":[{"url":"https://arxiv.org/abs/1912.10218","open_access":"1"}],"year":"2020","_id":"8285","doi":"10.1103/PhysRevLett.125.043202","quality_controlled":"1","date_updated":"2023-10-18T08:38:35Z","external_id":{"isi":["000552227400008"],"arxiv":["1912.10218"],"pmid":["32794788"]},"author":[{"first_name":"Benjamin K.","last_name":"Malia","full_name":"Malia, Benjamin K."},{"first_name":"Julián","last_name":"Martínez-Rincón","full_name":"Martínez-Rincón, Julián"},{"full_name":"Wu, Yunfan","last_name":"Wu","first_name":"Yunfan"},{"full_name":"Hosten, Onur","last_name":"Hosten","id":"4C02D85E-F248-11E8-B48F-1D18A9856A87","orcid":"0000-0002-2031-204X","first_name":"Onur"},{"full_name":"Kasevich, Mark A.","first_name":"Mark A.","last_name":"Kasevich"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87"}