N-Way Frequency Beamsplitter for Quantum Photonics

TL;DR

This paper introduces a method for simultaneous N-way coupling of optical frequency modes using four-wave mixing, enabling scalable quantum photonic networks with verified three-way interference.

Contribution

It proposes and experimentally demonstrates a scalable N-way frequency beamsplitter for quantum photonics, extending two-mode interactions to multiple modes.

Findings

Demonstrated three-way multiphoton interference in frequency modes

Generalized theory for N-mode frequency interactions

Potential for scalable quantum information processing

Abstract

Optical networks are the leading platform for the transfer of information due to their low loss and ability to scale to many information channels using optical frequency modes. To fully leverage the quantum properties of light in this platform, it is desired to manipulate higher-dimensional superpositions by orchestrating linear, beamsplitter-type interactions between several channels simultaneously. We propose a method of achieving simultaneous, all-to-all coupling between N optical frequency modes via N-way Bragg-scattering four-wave mixing. By exploiting the frequency degree of freedom, additional modes can be multiplexed in an interaction medium of fixed volume and loss, avoiding the introduction of excess noise. We generalize the theory of the frequency-encoded two-mode interaction to N modes under this four-wave mixing approach and experimentally verify the quantum nature of this scheme by demonstrating three-way multiphoton interference. The two input photons are shared among three frequency modes and display interference differing from that of two classical (coherent-state) inputs. These results show the potential of our approach for the scalability of photonic quantum information processing to general N-mode systems in the frequency domain.