Exceptional sensitivity near the bistable transition point of a hybrid quantum system

• URL: http://arxiv.org/abs/2507.09691v1
• Date: Sun, 13 Jul 2025 16:02:12 GMT
• Title: Exceptional sensitivity near the bistable transition point of a hybrid quantum system
• Authors: Hanfeng Wang, Kurt Jacobs, Donald Fahey, Yong Hu, Dirk R. Englund, Matthew E. Trusheim,
• Abstract summary: Phase transitions can dramatically alter system dynamics, unlocking new behavior and improving performance. Exceptional points (EPs) are particularly relevant for sensing applications as they can increase sensor response to external perturbations.<n>Here, we overcome this limitation using nonlinearity, which exhibits exceptional signal-to-noise ratio (SNR) enhancement around a bistable transition point (BP)<n>This result surpasses the sensitivity limit of an ideal, thermally-limited electron magnetometer and resolves a long-standing debate regarding EP-like physics in advanced quantum sensing.
• Score: 0.8390219473444447
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Phase transitions can dramatically alter system dynamics, unlocking new behavior and improving performance. Exceptional points (EPs), where the eigenvalues and corresponding eigenvectors of a coupled linear system coalesce, are particularly relevant for sensing applications as they can increase sensor response to external perturbations to a range of phenomena from optical phase shifts to gravitational waves. However, the coalescence of eigenstates at linear EPs amplifies noise, negating the signal-to-noise ratio (SNR) enhancement. Here, we overcome this limitation using nonlinearity, which exhibits exceptional SNR around a bistable transition point (BP). We couple a state-of-the-art diamond quantum sensor to a nonlinear Van der Pol oscillator, forming a self-oscillating hybrid system that exhibits both a single-valued and bistable phase. The boundaries between these phases are marked by both adiabatic and deterministic non-adiabatic transitions that enable chiral state switching and state coalescence at the BP. Crucially, NV magnetometry performed near the BP exhibits a 17x enhancement in SNR, achieving a record sensitivity of 170 fT/\sqrt{Hz}. This result surpasses the sensitivity limit of an ideal, thermally-limited electron magnetometer and resolves a long-standing debate regarding EP-like physics in advanced quantum sensing.

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