Enhancement of Sensitivity Near Exceptional Points in Dissipative Qubit‐Resonator Systems

Abstract Dissipation usually plays a negative role in quantum metrological technologies, which aim to improve measurement precision by leveraging quantum effects that are vulnerable to environment‐induced decoherence. Recently, it has been demonstrated that dissipation can actually be used as a favorable resource for enhancing the susceptibility of signal detection. However, demonstrations of such enhancement for detecting physical quantities in open quantum systems are still lacking. Here a protocol is proposed and demonstrated for realizing such non‐Hermitian quantum sensors for probing the coupling between a qubit and a resonator subjecting to energy dissipations. The excitation‐number conversion associated with the no‐jump evolution trajectory enables removal of the noisy outcomes with quantum jumps, implementing the exceptional point (EP), where the Rabi splitting exhibits a divergent behavior in response to a tiny variation of the effective coupling. The sensitivity enhancement near the EP is confirmed by both theoretical calculation and experimental measurement.