Oct 23 – 25, 2019
Aula Gerace
Europe/Rome timezone
We had been hoping to be able to hold the conference on the originally scheduled period in October 2021 but given the pandemic situation we have decided to postpone the conference period to October 2022.

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

Oct 23, 2019, 2:00 PM
Aula Gerace

Aula Gerace

Polo Fibonacci Edificio C Largo B. Pontecorvo, 3 56127 Pisa
talk Quantum Gases Talks on specific topics


Prof. Murray Holland (JILA and University of Colorado)


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 $\Delta\phi_{\text{SQL}}=1/\sqrt{N}\,\text{rad}$.

Available as: Athreya Shankar, Graham P. Greve, Baochen Wu, James K. Thompson, and Murray Holland, Phys. Rev. Lett. 122, 233602 (2019).

Primary authors

Prof. Murray Holland (JILA and University of Colorado) Mr Graham Greve (JILA and University of Colorado) Mr Baochen Wu (JILA and University of Colorado) Mr Athreya Shankar (JILA and University of Colorado) Prof. James Thompson (JILA and NIST, University of Colorado Boulder)

Presentation materials