Quantum Sensor’s Sensitivity Boosted by Multibody Interactions

Building on previous work showing that unstable points in a collective-spin system amplify weak signals, the researchers found that adding a quartic, or fourth-degree, nonlinear term to the system’s Hamiltonian creates new unstable points and accelerates amplification. Remarkably, even when maintaining a fixed instability rate, this system outperforms those relying on quadratic interactions due to enhanced short-time dynamics, identifying phase-space curvature as a key resource for optimizing sensor speed and performance. Adding a quartic spin coupling to existing quantum sensing systems generates additional unstable points and accelerates signal amplification, leading to enhanced sensitivity within experimentally achievable coherence times. The new research demonstrates that reshaping the phase-space structure with these additional interactions significantly improves performance. Specifically, the addition of this quartic coupling creates more unstable points, each exhibiting larger local Lyapunov exponents, and markedly enhances the growth rate of the gain. The team computed the fidelity,…