Multi-photon interference in the spectral domain by direct heralding of superposition states

TL;DR

This paper demonstrates multi-photon interference in the spectral domain using a single silicon waveguide, where frequency correlations produce superposition states across channels, simplifying quantum photonic state control.

Contribution

It introduces a method to observe multi-photon interference via spectral correlations without requiring a large unitary interferometer, simplifying quantum photonic state manipulation.

Findings

Interference observed in four-photon events from a single silicon waveguide.

Frequency correlations enable superposition states across multiple channels.

Spectral engineering can replace complex interferometers in quantum photonics.

Abstract

Multi-photon interference is central to photonic quantum information processing and quantum simulation, usually requiring multiple sources of non-classical light followed by a unitary transformation on their modes. Here, we observe interference in the four-photon events generated by a single silicon waveguide, where the different modes are six frequency channels. Rather than requiring a unitary transformation, the frequency correlations of the source are configured such that photons are generated in superposition states across multiple channels, and interference effects can be seen without further manipulation. This suggests joint spectral engineering is a tool for controlling complex quantum photonic states without the difficulty of implementing a large unitary interferometer, which could have practical benefits in various applications of multi-photon interference.