Cascaded Multiparameter Quantum Metrology

We present an innovative, platform-independent concept for multiparameter sensing where the measurable parameters are in series, or cascaded, enabling measurements as a function of position. With temporally resolved detection, we show that squeezing can give a quantum enhancement in sensitivity over that of classical states by a factor of $e^{2r}$, where $r \approx 1$ is the squeezing parameter. As an example, we have modeled an interferometer that senses multiple phase shifts along the same path, demonstrating a maximal quantum advantage by combining a coherent state with squeezed vacuum. Further classical modeling with up to 100 phases shows linear scaling potential for adding nodes to the sensor. The approach represents a new paradigm in multiparameter quantum metrology, and can be applied to remote sensing, geophysical surveying, and infrastructure monitoring.