Quantum noise in a squeezed-light-enhanced multiparameter quantum sensor

TL;DR

This paper demonstrates quantum-enhanced sensitivity in a multi-parameter magnetometer using squeezed light, revealing fundamental noise trade-offs and the complex interplay of quantum noise sources in the sensor.

Contribution

It introduces a hybrid dc-rf optically pumped magnetometer that utilizes squeezed light to control quantum noise distribution, advancing multi-parameter quantum sensing techniques.

Findings

Quantum enhancement achieved in a multi-parameter sensor

Interaction of photon shot noise, spin projection noise, and back-action noise analyzed

Trade-offs between sensitivity, back-action, and bandwidth demonstrated

Abstract

We study quantum enhancement of sensitivity using squeezed light in a multi-parameter quantum sensor, the hybrid dc-rf optically pumped magnetometer (hOPM) [Phys. Rev. Applied 21, 034054, (2024)]. Using a single spin ensemble, the hOPM acquires both the dc field strength (scalar magnetometry), and resonantly detects one quadrature of the ac magnetic field at a chosen frequency (rf magnetometry). In contrast to the Bell-Bloom scalar magnetometer [Phys. Rev. Lett. 127, 193601 (2021)], the back-action evasion in the hOPM is incomplete, leading to a nontrivial interplay of the three quantum noise sources in this system: photon shot noise, spin projection noise, and measurement back-action noise. We observe these interactions using squeezed light as a tool to control the distribution of optical quantum noise between $S_2$ and $S_3$ polarization Stokes components, and the resulting effect on readout quantum noise and measurement back-action. These results demonstrate quantum-enhanced sensitivity in a continuously operating multi-parameter sensor and reveal fundamental trade-offs between sensitivity, back-action, and bandwidth.