Instability-Enhanced Quantum Sensing with Tunable Multibody Interactions

TL;DR

This paper demonstrates that multibody interactions in quantum systems can significantly enhance sensing capabilities by exploiting dynamical instabilities, leading to faster and more sensitive quantum sensors.

Contribution

It introduces a quartic Hamiltonian extension that increases amplification and sensitivity in quantum sensing beyond quadratic models, with potential experimental applications.

Findings

Quartic interactions reshape phase-space and create new unstable points.

Multibody interactions outperform quadratic models at fixed instability rates.

Enhanced sensitivity achieved within accessible coherence times.

Abstract

Dynamical instabilities can amplify small perturbations into measurable signals, offering a route to quantum-enhanced sensing. This mechanism was experimentally demonstrated in a collective-spin system with quadratic interactions, described by a twisting-and-turning Hamiltonian, where quantum evolution near an unstable point leads to exponential growth of spin fluctuations, enabling metrological gain beyond the standard quantum limit. Here, we show that a quartic extension of this Hamiltonian substantially increases the amplification. The additional nonlinear term reshapes the phase-space structure, generating new unstable points and accelerating signal amplification. As a result, enhanced sensitivity is achieved within experimentally accessible coherence times. Remarkably, even at fixed instability rate (equal Lyapunov exponent), multibody interactions outperform the quadratic case due to enhanced short-time dynamics. We analyze the classical and quantum behavior of the multibody model and discuss its experimental implementations. Our results identify phase-space curvature as a resource for optimizing the speed and performance of quantum sensors.