Squeezed-Light Enhancement and Backaction Evasion in a High Sensitivity Optically Pumped Magnetometer

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Measurement Science

Background:

• Optically pumped magnetometers (OPMs) are sensitive quantum measurement devices.
• Performance is often limited by quantum noise, including spin projection noise and photon shot noise.
• Bell-Bloom (BB) optical pumping is a technique used for OPMs.

Purpose of the Study:

• To investigate the impact of optical polarization squeezing on OPM performance.
• To demonstrate the evasion of measurement backaction noise.
• To develop a theoretical model for quantum noise dynamics in BB magnetometers.

Main Methods:

• Utilized Bell-Bloom optical pumping of ^{87}Rb vapor.
• Employed Faraday rotation for detecting spin precession.
• Applied probe polarization squeezing to the magnetometer setup.

Main Results:

• Achieved sub-pT/sqrt[Hz] sensitivity, limited by spin projection noise and photon shot noise.
• Demonstrated improved high-frequency sensitivity and increased measurement bandwidth using polarization squeezing.
• Showcased evasion of measurement backaction noise without sensitivity loss.

Conclusions:

• Optical polarization squeezing offers a viable method to enhance OPM performance.
• The developed model explains noise reduction and backaction shunting via squeezing.
• The technique is compatible with high-density and multipass methods for extreme sensitivity.