Southwest Quantum Information and Technology

Deterministic spin squeezing with continuous feedback control

Presenting Author: Senthilnathan Lingasamy, University of Arizona
Contributing Author(s): Daniel Hemmer, Ivan Deutsch, Poul Jessen

We demonstrate preparation of a deterministically squeezed collective spin state of about a million Cs atoms using continuous quantum non-demolition (QND) measurement and real-time radio-frequency (RF) magnetic field feedback. In our experiment, laser-cooled Cs atoms are optically pumped to the |f=4,mf=4> state and a pi/2 RF pulse is applied to steer the spins to the desired spin coherent state (SCS). After this initial state preparation, we perform a QND measurement of the Fz component of the collective spin with an off-resonant probe laser beam. The measured value is fed to a controller that applies real-time RF feedback. By doing so, we are able to correct for state preparation errors and deterministically squeeze the variance of the SCS (standard quantum limit) to the ‘shot-noise limit’. This feedback control strategy can be extended to perform real-time atomic magnetometry.

(Session 5 : Thursday from 5:00pm - 7:00 pm)