Multi-Colour Quantum Metrology with Entangled Photons

TL;DR

This paper demonstrates that entangled photon pairs of two different colours can achieve measurement sensitivities beyond classical limits, using a simple and robust interferometric setup with multi-photon entanglement.

Contribution

It introduces a method for multi-colour entangled photon states in quantum metrology, achieving supersensitivity and super-resolution with a practical setup.

Findings

Achieved sensitivity beyond the standard quantum limit.

Demonstrated super-resolved interference fringes with multi-photon entanglement.

Used a photonic crystal fibre source for entangled photon pairs.

Abstract

Entangled photons can be used to make measurements with an accuracy beyond that possible with classical light. While most implementations of quantum metrology have used states made up of a single colour of photons, we show that entangled states of two colours can show supersensitivity to optical phase and path-length by using a photonic crystal fibre source of photon pairs inside an interferometer. This setup is relatively simple and robust to experimental imperfections. We demonstrate sensitivity beyond the standard quantum limit and show super-resolved interference fringes using entangled states of two, four, and six photons.