Stable Atomic Magnetometer in Parity-Time Symmetry Broken Phase

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.

6+18 pages, 4+8 figures, to be published in Physical Review Letters

References in corpus (7)

• Making Sense of Non-Hermitian Hamiltonians
• Non-Hermitian Ring Laser Gyroscopes with Enhanced Sagnac Sensitivity
• A microfabricated optically-pumped magnetic gradiometer
• ${}^3$He-${}^{129}$Xe Comagnetometery using ${}^{87}$Rb Detection and Decoupling
• New classes of systematic effects in gas spin co-magnetometers
• Continuous Comagnetometry using Transversely Polarized Xe Isotopes
• General Solution to Gradient Induced Transverse and Longitudinal Relaxation of Spins Undergoing Restricted Diffusion

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