Tuneable quantum interference in a 3D integrated circuit

TL;DR

This paper demonstrates tunable two-photon quantum interference in a 3D integrated photonic circuit, enabling enhanced phase measurement capabilities approaching quantum limits.

Contribution

It introduces a 3D multi-path interferometer with tunable quantum interference, advancing integrated photonics for quantum computing and metrology.

Findings

Reduced interference periodicity and increased visibility.

Non-classical visibilities are widely tunable.

Fisher information approaches the quantum maximum.

Abstract

Integrated photonics promises solutions to questions of stability, complexity, and size in quantum optics. Advances in tunable and non-planar integrated platforms, such laser-inscribed photonics, continue to bring the realisation of quantum advantages in computation and metrology ever closer, perhaps most easily seen in multi-path interferometry. Here we demonstrate control of two-photon interference in a chip-scale 3D multi-path interferometer, showing a reduced periodicity and enhanced visibility compared to single photon measurements. Observed non-classical visibilities are widely tunable, and explained well by theoretical predictions based on classical measurements. With these predictions we extract a Fisher information approaching a theoretical maximum, demonstrating the capability of the device for quantum enhanced phase measurements.