Entanglement-enhanced quantum metrology in a noisy environment

TL;DR

This paper demonstrates that entanglement with ancillary qubits can enhance quantum phase estimation in noisy environments, using a photonic experiment with practical linear-optical setups, advancing quantum metrology's robustness.

Contribution

It introduces a practical entanglement-assisted quantum metrology method that improves phase estimation under noise using simple linear-optical interferometers.

Findings

Entanglement enhances quantum Fisher information in noisy channels.

Assisted entanglement fails for individual noisy channels but works in combined scenarios.

Experimental validation with photonic interferometers shows practical advantages.

Abstract

Quantum metrology overcomes standard precision limits and plays a central role in science and technology. Practically it is vulnerable to imperfections such as decoherence. Here, we demonstrate quantum metrology for noisy channels such that entanglement with ancillary qubits enhances the quantum Fisher information for phase estimation but not otherwise. Our photonic experiment covers a range of noise for various types of channels, including for two randomly alternating channels such that assisted entanglement fails for each noisy channel individually. We have simulated noisy channels by implementing space-multiplexed dual interferometers with quantum photonic inputs. We have demonstrated the advantage of entanglement-assisted protocols in phase estimation experiment run with either single-probe or multi-probe approach. These results establish that entanglement with ancillae is a valuable approach for delivering quantum-enhanced metrology. Our new approach to entanglement-assisted quantum metrology via a simple linear-optical interferometric network with easy-to-prepare photonic inputs provides a path towards practical quantum metrology.