# Experimental multiphase estimation on a chip

## TL;DR

This paper demonstrates a reconfigurable integrated multimode interferometer capable of quantum-enhanced multiphase estimation, showcasing high-fidelity operation and potential for testing advanced adaptive protocols in quantum metrology.

## Contribution

The authors experimentally implement a reconfigurable integrated multimode interferometer for simultaneous two-phase estimation, advancing quantum metrology platforms.

## Key findings

- Quantum-enhanced two-phase estimation achieved
- High-fidelity operation of the interferometer verified
- Device suitable for testing adaptive multiphase protocols

## Abstract

Multiparameter estimation is a general problem that aims at measuring unknown physical quantities, obtaining high precision in the process. In this context, the adoption of quantum resources promises a substantial boost in the achievable performances with respect to the classical case. However, several open problems remain to be addressed in the multiparameter scenario. A crucial requirement is the identification of suitable platforms to develop and experimentally test novel efficient methodologies that can be employed in this general framework. We report the experimental implementation of a reconfigurable integrated multimode interferometer designed for the simultaneous estimation of two optical phases. We verify the high-fidelity operation of the implemented device, and demonstrate quantum-enhanced performances in two-phase estimation with respect to the best classical case, post-selected to the number of detected coincidences. This device can be employed to test general adaptive multiphase protocols due to its high reconfigurability level, and represents a powerful platform to investigate the multiparameter estimation scenario.