Quantum noise sensing: fundamental limits, protocol designs and application in quantum transduction

Noise is ubiquitous and carries critical information. Bosonic additive noise models are fundamental in numerous applications, including force sensing with optomechanical sensors and dark matter searches using microwave cavities. In this talk, we summarize recent progress in understanding the fundamental precision limits of noise sensing, developing protocols that leverage quantum effects such as squeezing and entanglement, and applying these protocols to enhance quantum transduction systems.

First, we establish an upper bound on the quantum Fisher information for bosonic noise sensing in the presence of loss. We demonstrate that this bound can be achieved with access to noiseless entangled ancilla. However, when all modes experience loss, the Rayleigh limit imposes significant constraints, making it challenging to surpass the performance of vacuum states and photon counting. We propose protocols to mitigate the impact of the Rayleigh limit.

Additionally, we extend noise sensing to multi-mode correlated noise scenarios, where quantum machine learning techniques exhibit notable advantages. Finally, we apply concepts from entanglement-assisted quantum sensing to quantum transduction. Specifically, we design a protocol that enhances microwave-optical quantum transduction efficiency by utilizing either microwave-microwave or optical-optical entanglement.