States of an ensemble of two-level atoms with reduced quantum uncertainty

We generate entangled states of an ensemble of 5x10{4} 87Rb atoms by optical quantum nondemolition measurement. The resonator-enhanced measurement leaves the atomic ensemble, prepared in a superposition of hyperfine clock levels, in a squeezed spin state. By comparing the resulting reduction of quan...

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Bibliographic Details
Published in:Physical review letters 2010-02, Vol.104 (7), p.073604-073604, Article 073604
Main Authors: Schleier-Smith, Monika H, Leroux, Ian D, Vuletić, Vladan
Format: Article
Language:English
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Summary:We generate entangled states of an ensemble of 5x10{4} 87Rb atoms by optical quantum nondemolition measurement. The resonator-enhanced measurement leaves the atomic ensemble, prepared in a superposition of hyperfine clock levels, in a squeezed spin state. By comparing the resulting reduction of quantum projection noise [up to 8.8(8) dB] with the concomitant reduction of coherence, we demonstrate a clock input state with spectroscopic sensitivity 3.0(8) dB beyond the standard quantum limit.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.104.073604