Southwest Quantum Information and Technology

Deterministic squeezing and closed-loop magnetometry with a collective atomic spin

Presenting Author: Daniel Hemmer, University of Arizona
Contributing Author(s): David Melchior, Ezad Shojaee, Ivan Deutsch, Poul Jessen

Measurements with quantum limited resolution have important applications in metrology and sensing, including atomic clocks, atom interferometry, and magnetometry. In our work we perform a quantum-non-demolition measurement on the collective angular momentum from a million spin-4 Cs atoms. Through quantum backaction this measurement generates upwards of 4.5 dB metrologically relevant spin squeezing. By introducing real-time feedback, we can use the collective spin to perform precision magnetometry with resolution below the standard quantum limit. In the past our ability to leverage squeezing and quantum feedback has been limited by a noisy field environment. We have therefore rebuilt our experiment inside a multi-layered magnetic shield of mu-metal and aluminum, where background fields are reduced by a factor >10,000 at frequencies up to tens of kHz. We report on progress towards composite-pulse control, which will allow us to detect and correct classical control errors such as noisy rotations of the collective spin. The shielded environment will also allow us to better evaluate and optimize the performance of our closed-loop magnetometer.

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