Quantum Locking of Intrinsic Spin Squeezed State in Earth-field-range Magnetometry

TL;DR

This paper demonstrates a quantum locking technique to stabilize an intrinsic spin squeezed state caused by the nonlinear Zeeman effect, enabling quantum-enhanced sensitivity in Earth-field-range magnetometry.

Contribution

It introduces a method to lock the oscillating spin squeezed state, turning the nonlinear Zeeman effect into a quantum advantage for magnetometry.

Findings

Quantum locking stabilizes the intrinsic spin squeezed state.

Enhanced sensitivity in Earth-field-range magnetometers.

Turned a physical limitation into a quantum sensing benefit.

Abstract

In the Earth-field range, the nonlinear Zeeman (NLZ) effect has been a bottleneck limiting the sensitivity and accuracy of atomic magnetometry from physical mechanism. To break this bottleneck, various techniques are introduced to suppress the NLZ effect. Here we revisit the spin dynamics in the Earth-field-range magnetometry and identify the existence of the intrinsic spin squeezed state (SSS) generated from the geomagnetically induced NLZ effect with the oscillating squeezing degree and squeezing axis. Such oscillating features of the SSS prevent its direct observation and as well, accessibility to magnetic sensing. To exploit quantum advantage of the intrinsic SSS in the Earth-field-range magnetometry, it's essential to lock the oscillating SSS to a persistent one. Hence, we develop a quantum locking technique to achieve a persistent SSS, benefiting from which the sensitivity of the Earth-field-range magnetometer is quantum-enhanced. This work presents an innovative way turning the drawback of NLZ effect into the quantum advantage and opens a new access to quantum-enhanced magnetometry in the Earth-field range.