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APS » Journals » Phys. Rev. Lett. » Volume 82 » Issue 23
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Phys. Rev. Lett. 82, 4619–4622 (1999)

Quantum Projection Noise in an Atomic Fountain: A High Stability Cesium Frequency Standard

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G. Santarelli, Ph. Laurent, P. Lemonde, and A. Clairon
BNM-LPTF, Observatoire de Paris, 61 Avenue de l'Observatoire, 75014 Paris, France

A. G. Mann, S. Chang, and A. N. Luiten
Physics Department, University of Western Australia, Nedlands, 6907 Western Australia, Australia

C. Salomon
Laboratoire Kastler Brossel, ENS, 24 rue Lhomond, 75005 Paris, France

Received 29 October 1998; published in the issue dated 7 June 1999

See accompanying Physics Focus

We describe the operation of a laser cooled cesium fountain clock in the quantum limited regime. An ultrastable cryogenic sapphire oscillator is used to measure the short-term frequency stability of the fountain as a function of the number of detected atoms Nat. For Nat varying from 4×104 to 6×105 the Allan standard deviation of the frequency fluctuations is in excellent agreement with the Nat-1/2 law of atomic projection noise. With 6×105 atoms, the relative frequency stability is 4×10-14τ-1/2, where τ is the integration time in seconds. This is the best short-term stability ever reported for primary frequency standards, a factor of 5 improvement over previous results.

© 1999 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.82.4619
DOI:
10.1103/PhysRevLett.82.4619
PACS:
32.80.Pj, 06.30.Ft, 42.50.Lc
 
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