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arXiv · 0808.0516

Spin squeezing of atomic ensembles by multi-colour quantum non-demolition measurements

M. Saffman·D. Oblak·J. Appel·E. S. Polzik
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Abstract

We analyze the creation of spin squeezed atomic ensembles by simultaneous dispersive interactions with several optical frequencies. A judicious choice of optical parameters enables optimization of an interferometric detection scheme that suppresses inhomogeneous light shifts and keeps the interferometer operating in a balanced mode that minimizes technical noise. We show that when the atoms interact with two-frequency light tuned to cycling transitions the degree of spin squeezing $ξ^2$ scales as $ξ^2\sim 1/d$ where $d$ is the resonant optical depth of the ensemble. In real alkali atoms there are loss channels and the scaling may be closer to $ξ^2\sim 1/\sqrt d.$ Nevertheless the use of two-frequencies provides a significant improvement in the degree of squeezing attainable as we show by quantitative analysis of non-resonant probing on the Cs D1 line. Two alternative configurations are analyzed: a Mach-Zehnder interferometer that uses spatial interference, and an interaction with multi-frequency amplitude modulated light that does not require a spatial interferometer.

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M. Saffman, D. Oblak, J. Appel, E. S. Polzik. 2009-05-14. Spin squeezing of atomic ensembles by multi-colour quantum non-demolition measurements. https://doi.org/10.1103/physreva.79.023831

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