Continuous Real-Time Tracking of a Quantum Phase Below the Standard Quantum Limit

Author
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 of Publication
2019
Journal
Physical Review Letters
Volume
122
Date Published
2019-06
ISSN Number
0031-9007
URL
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.233602
DOI
10.1103/PhysRevLett.122.233602
JILA PI
Associated Institutes
Journal Article