2018/09/30 by Athreya Shankar, Graham P. Greve, Baochen Wu +2 · 1 citation
Computer Science · Mathematics · Physics and Astronomy · #Atomic and Subatomic Physics Research #Cold Atom Physics and Bose-Einstein Condensates #Heisenberg limit #Limit (mathematics) #Lossy compression #Mathematics #Phase (matter) #Physics #Population #Quantum #Quantum Information and Cryptography #Quantum information #Quantum limit #Quantum mechanics #Quantum network #Spin (aerodynamics) #Statistics #physics.atom-ph #quant-ph
paper · pdf · doi:10.1103/physrevlett.122.233602
published as Phys. Rev. Lett. 122, 233602 (2019) · 6 + 6 pages, 3 + 2 figures, includes Supplemental Material; close to journal version
openalex publication_date 2019/06/13 · arxiv created 2019/06/19 · arxiv updated 2019/06/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We propose a scheme for continuously measuring the evolving quantum phase of a 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 ΔϕSQL=1/sqrt[N] rad.