Reducing collective quantum state rotation errors with reversible dephasing

@article{Cox2014ReducingCQ,
  title={Reducing collective quantum state rotation errors with reversible dephasing},
  author={Kevin C Cox and Matthew A. Norcia and Joshua M. Weiner and Justin Gary Bohnet and James K. Thompson},
  journal={Applied Physics Letters},
  year={2014},
  volume={105},
  pages={261102}
}
We demonstrate that reversible dephasing via inhomogeneous broadening can greatly reduce collective quantum state rotation errors, and observe the suppression of rotation errors by more than 21 dB in the context of collective population measurements of the spin states of an ensemble of 2.1×105 laser cooled and trapped 87Rb atoms. The large reduction in rotation noise enables direct resolution of spin state populations 13(1) dB below the fundamental quantum projection noise limit. Further, the… 

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