Stable Atomic Magnetometer in Parity-Time Symmetry Broken Phase

TL;DR

This paper demonstrates that by exploiting a parity-time symmetry transition in diffusive spins under magnetic field gradients, one can develop a stable atomic magnetometer insensitive to long-term drifts, enhancing weak signal detection.

Contribution

It introduces a novel approach using PT symmetry breaking in spin systems to achieve stable, drift-insensitive magnetic field measurements.

Findings

Observation of PT phase transition in diffusive spins.

Spin precession frequency splitting in the broken phase.

Development of a drift-insensitive magnetometer.

Abstract

Random motion of spins is usually detrimental in magnetic resonance experiments. The spin diffusion in non-uniform magnetic fields causes broadening of the resonance and limits the sensitivity and the spectral resolution in applications like magnetic resonance spectroscopy. Here, by observation of the parity-time ($PT$) phase transition of diffusive spins in gradient magnetic fields, we show that the spatial degrees of freedom of atoms could become a resource, rather than harmfulness, for high-precision measurement of weak signals. In the normal phase with zero or low gradient fields, the diffusion results in dissipation of spin precession. However, by increasing the field gradient, the spin system undergoes a $PT$ transition, and enters the $PT$ symmetry broken phase. In this novel phase, the spin precession frequency splits due to spatial localization of the eigenmodes. We demonstrate that, using these spatial-motion-induced split frequencies, the spin system can serve as a stable magnetometer, whose output is insensitive to the inevitable long-term drift of control parameters. This opens a door to detect extremely weak signals in imperfectly controlled environment.