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Q: Fachverband Quantenoptik und Photonik

Q 30: Poster II

Q 30.54: Poster

Tuesday, March 3, 2009, 16:30–19:00, VMP 9 Poster

Experimental demonstration of spin squeezing on the clock transition — •Patrick Windpassinger, Daniel Oblak, Ulrich Hoff, Jürgen Appel, Niels Kjaergaard, and Eugene S. Polzik — QUANTOP, Niels Bohr Institute, Copenhagen, Denmark

The so-called projection noise of an ensemble of uncorrelated atoms is a current limitation to the precision of atomic clocks. In recent experiments on dipole trapped ensembles of Cs atoms in an equal superposition of the clock states we have observed the quantum projection noise by interrogations using off-resonant probe laser light. Since the dispersive light-atom interaction has a quantum nondemolition measurement character we can use the information gained when applying a probe pulse of light to predict the outcome of a subsequent measurement beyond the standard quantum limit. Hence a reduction or ``squeezing'' of the population difference is encountered. Since a two-level quantum system is equivalent to a spin 1/2 particle this is referred to a pseudo-spin squeezing. The observation of squeezing implies that the particles in the ensemble are non-classically correlated (entangled). When taking into account decoherence resulting from spontaneously scattered probe photons our experiments show about 3 dB of spectroscopically relevant squeezing (noise reduction).

[1] D. Oblak et al., Phys. Rev. A 71, 043807 (2005)

[2] P. Windpassinger et al, Phys. Rev. Lett. 100, 103601 (2008)

[3] J. Appel et al., arXiv:0810.3545 (2008)