Amplified response of cavity-coupled quantum-critical systems

Quantum critical systems represent an exceptional resource for quantum metrology, as their diverging susceptibilities and long-range entanglement enhance the system’s response to weak perturbations. Here we investigate how these critical quantum fluctuations amplify light–matter correlations when a quantum critical mode is embedded in a quantized cavity [1]. By coupling the critical field bilinearly to the photon mode, we show that the quantum Fisher information, squeezing, and entanglement between photons and matter are all markedly enhanced near criticality. The resulting hybrid system exhibits a superradiant transition at asymptotically small coupling strengths, identifying a regime where quantum criticality acts as a natural amplifier of metrological precision. Our findings establish a general principle linking criticality, cavity-mediated interactions, and quantum enhancement, opening a new pathway for exploiting correlated quantum materials as precision quantum sensors and resources for nonclassical state engineering.