36_squeeze_col_spin
Enhanced Squeezing of a Collective Spin via Control of Its Qudit Subsystems
Leigh M. Norris1,2, Collin M. Trail3, Poul S. Jessen1,4, Ivan H. Deutsch1,2
1. Center for Quantum Information and Control (CQuIC)
2. Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131-0001, USA
3. Institute for Quantum Information Science, University of Calgary, Calgary, Alberta, Canada T2N 1N4
4. College of Optical Sciences and Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
Unitary control of qudits can improve the collective spin squeezing of an atomic ensemble. Preparing the atoms in a state with large quantum fluctuations in magnetization strengthens the entangling Faraday interaction. The resulting increase in interatomic entanglement can be converted into metrologically useful spin squeezing. Further control can squeeze the internal atomic spin without compromising entanglement, providing an overall multiplicative factor in the collective squeezing. We model the effects of optical pumping and study the tradeoffs between enhanced entanglement and decoherence. For realistic parameters we see improvements of ~10 dB.