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Ultraprecise Magnetometry with Spinor Bose-Einstein Condensates

Dr Lincoln Turner

School of Physics, Monash University

3:30 pm Friday, 27 June 2008, EN102 (Ground Floor, EN Building), Hawthorn.

Holding Bose-Einstein condensates (BECs) in far off-resonant optical dipole traps leaves the condensate's spin free. Such "spinor condensates" show complex interaction between spin and spatial structure such as spontaneous symmetry breaking into ferromagnetic domains. The spatial coupling can be supressed, however, allowing the BEC to behave as "one big spin". Faraday spectroscopy provides a promising minimally-destructive measurement of this macroscopic spin state. I will describe how Faraday measurement of a single-mode spinor condensate will make an ultraprecise magnetometer microscope with picotesla/root-Hz sensitivity exceeding the current state-of-the-art SQUID sensors. Collisions between the Zeeman components of the BEC complicate the picture. The mean-field dynamics of these interaction is now well understood, and we are starting to explore the many-body quantum dynamics. Spinor BEC appears to be an outstanding low-decoherence system for studying measurement-induced squeezing, spin self-squeezing, spontaneous cat states and "quantum carpets". These coherent many-body processes may allow the spinor magnetometer to detect magnetic fields below the standard quantum limit.

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