# Retrieving ideal precision in noisy quantum optical metrology

## TL;DR

This paper demonstrates that in quantum optical metrology, the Zeno limit can be asymptotically recovered despite photon loss by leveraging non-Markovian effects and bound states, enabling ultrasensitive measurements.

## Contribution

It reveals that non-Markovian photon dissipation can restore the Zeno limit in quantum metrology, guiding reservoir engineering for enhanced measurement precision.

## Key findings

- ZL can be asymptotically recovered with non-Markovian dissipation
- Formation of bound states explains noise effects
- Guidelines for reservoir engineering in quantum metrology

## Abstract

Quantum metrology employs quantum effects to attain a measurement precision surpassing the limit achievable in classical physics. However, it was previously found that the precision returns the shot-noise limit (SNL) from the ideal Zeno limit (ZL) due to the photon loss in quantum metrology based on Mech-Zehnder interferometer. Here, we find that not only the SNL can be beaten, but also the ZL can be asymptotically recovered in long-encoding-time condition when the photon dissipation is exactly studied in its inherent non-Markovian manner. Our analysis reveals that it is due to the formation of a bound state of the photonic system and its dissipative noise. Highlighting the microscopic mechanism of the dissipative noise on the quantum optical metrology, our result supplies a guideline to realize the ultrasensitive measurement in practice by forming the bound state in the setting of reservoir engineering.