Observation of Criticality-Enhanced Quantum Sensing in Nonunitary Quantum Walks

TL;DR

This paper experimentally demonstrates how non-Hermitian quantum walks can leverage criticality to enhance quantum sensing sensitivity, showing improved parameter estimation near phase transitions in a photonic system.

Contribution

It presents the first experimental realization of criticality-enhanced quantum sensing using nonunitary quantum walks with photonic systems.

Findings

Enhanced sensitivity observed at phase transitions

Criticality-driven scaling laws demonstrated

Transient times suffice for high-precision estimation

Abstract

Quantum physics enables parameter estimation with precisions beyond the capability of classical sensors. Quantum criticality is a key resource for this quantum-enhanced sensing, but experimental realization has been challenging due to the complexity of ground-state preparation and the long time required to reach the steady state near criticality. Here, we experimentally demonstrate critical enhancement in a non-Hermitian topological system using a photonic quantum walk setup. Our system supports two distinct phase transitions at which enhanced sensitivity is observed even at transient times for which the Bayesian inference shows excellent estimation and precision. It is a direct demonstration of criticality-enhanced scaling laws with non-unitary dynamics.