Collective spin squeezing of atoms in magnetic field-sensitive states

Presenting Author: Daniel Hemmer, University of Arizona
Contributing Author(s): Senthilnathan Lingasamy, Ezad Shojaee, Ivan Deutsch, Poul Jessen

Collective spin squeezing can be generated from a QND measurement of the relevant spin component through quantum backaction. When starting from a spin coherent state (SCS), our experiment can generate more than 3 dB of metrologically relevant spin squeezing, closely matching theoretical predictions. Our main objective is now to use control of the internal atomic spin to improve squeezing. For example, we can coherently map the internal spins from the SCS to a “cat” state, which increases the QPN by a factor of 2f=8 relative to the SCS [1]. This leads to increased backaction and entanglement produced by our QND measurement. The squeezing in this cat state basis can in principle be mapped back to the spin SCS basis where it will correspond to squeezing of the physical spin. A preliminary result suggests that up to 8 dB of metrologically useful squeezing can be generated if there are no control errors. Going forward, the main experimental challenge appears to be fluctuating background magnetic fields at frequencies up to tens of kHz, which interfere with control of the magnetic field-sensitive internal atomic spin states. We report on progress using a combination of mu-metal and aluminum shielding to suppress these fields. Once these fields have been suppressed to an acceptable level, we can use composite pulse sequences to measure and correct for control errors due to remaining experimental imperfections. [1] L.M. Norris et al., Phys. Rev. Lett. 109, 173603 (2012)

(Session 5 : Thursday from 5:00pm - 7:00 pm)


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