Efficient Information Retrieval for Sensing via Continuous Measurement

Continuous monitoring of driven-dissipative quantum-optical systems is a crucial element in the implementation of quantum metrology, providing essential strategies for achieving highly precise measurements beyond the classical limit. In this context, the relevant figure of merit is the quantum Fisher information of the radiation field emitted by the driven-dissipative sensor. Saturation of the corresponding precision limit as defined by the quantum Crame ' r-Rao bound is typically not achieved by conventional, temporally local continuous-measurement schemes such as counting or homodyning. To address the outstanding open challenge of efficient retrieval of the quantum Fisher information of the emission field, we design a novel continuous-measurement strategy featuring temporally quasilocal measurement bases as captured by matrix-product states. Such a measurement can be implemented effectively by injecting the emission field of the sensor into an auxiliary open system, a quantum-decoder module, which decodes specific input matrix-product states into simple product states as its output field, and performing conventional continuous measurement at the output. We devise a universal recipe for the construction of the decoder by exploiting the time-reversal transformation of quantum-optical input-output channels, thereby establishing a universal method to achieve the quantum Crame ' r-Rao precision limit for generic sensor designs based on continuous measurement. As a by-product, we establish an effective formula for the evaluation of the quantum Fisher information of the emission field of generic drivendissipative open sensors. We illustrate the power of our scheme with paramagnetic open sensor designs including linear force sensors, fiber-interfaced nonlinear emitters, and driven-dissipative many-body sensors, and demonstrate that it can be robustly implemented under realistic experimental imperfections.

Automated summary

Continuous monitoring of driven-dissipative quantum-optical systems is crucial for achieving highly precise measurements beyond the classical limit. We design a novel continuous-measurement strategy and develop a universal method to efficiently retrieve the quantum Fisher information. We also establish an effective formula for evaluating the quantum Fisher information of the emission field of driven-dissipative open sensors.