@article{11874,
  author = {Athreya Shankar and Graham Greve and Baochen Wu and James Thompson and Murray Holland},
  title = {Continuous Real-Time Tracking of a Quantum Phase Below the Standard Quantum Limit},
  abstract = {collective spin composed of N pseudospins. Quantum nondemolition measurements of a lossy cavity mode interacting with an atomic ensemble are used to directly probe the phase of the collective atomic spin without converting it into a population difference. Unlike traditional Ramsey measurement sequences, our scheme allows for real-time tracking of time-varying signals. As a bonus, spin-squeezed states develop naturally, providing real-time phase estimation significantly more precise than the standard quantum limit of Δ<em>ϕ</em><sub>SQL</sub>=1/√<em>N</em> rad.},
  year = {2019},
  journal = {Physical Review Letters},
  volume = {122},
  pages = {233602},
  month = {2019-06},
  issn = {0031-9007},
  url = {https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.233602},
  doi = {10.1103/PhysRevLett.122.233602},
}