Practical Quantum Metrology

TL;DR

This paper demonstrates a practical, loss-tolerant quantum metrology scheme that leverages multi-photon components from spontaneous parametric downconversion, achieving a 28% quantum advantage in optical phase measurement despite high system loss.

Contribution

It introduces a loss-tolerant quantum metrology approach that requires no additional state engineering and utilizes existing quantum-optical technology.

Findings

Achieved 28% quantum advantage in phase measurement precision.

Demonstrated robustness of the scheme under 83% system loss.

Utilized multi-photon components from spontaneous parametric downconversion.

Abstract

Quantum metrology research promises approaches to build new sensors that achieve the ultimate level of precision measurement and perform fundamentally better than modern sensors. Practical schemes that tolerate realistic fabrication imperfections and environmental noise are required in order to realise quantum-enhanced sensors and to enable their real-world application. We have demonstrated the key enabling principles of a practical, loss-tolerant approach to photonic quantum metrology designed to harness all multi-photon components in spontaneous parametric downconversion---a method for generating multiple photons that we show requires no further fundamental state engineering for use in practical quantum metrology. We observe a quantum advantage of 28% in precision measurement of optical phase using the four-photon detection component of this scheme, despite 83% system loss. This opens the way to new quantum sensors based on current quantum-optical capabilities.