High-dimensional frequency crystals and quantum walks in electro-optic microcombs

TL;DR

This paper introduces high-dimensional optical frequency crystals created within electro-optic microcombs, enabling the study of complex quantum phenomena and topologies in a controllable, on-chip platform with experimental validation across multiple dimensions.

Contribution

It proposes and demonstrates the creation of arbitrary-dimensional frequency crystals in electro-optic microcombs, linking their spectra to density-of-states and exploring quantum dynamics in synthetic lattices.

Findings

Validated one- to four-dimensional frequency crystals experimentally.

Observed quantum random walks and Bloch oscillations in the frequency domain.

Established a quantum description linking phase modulation to crystal properties.

Abstract

Synthetic optical structures have enabled studies of various physical processes and discoveries of new phenomena in a controllable manner. Past realizations, using for example coupled optical waveguides, were however limited in size and dimensionality. Here we theoretically propose and experimentally demonstrate optical frequency crystals of arbitrary dimensions, formed by hundreds of coupled spectral modes within an on-chip electro-optic frequency comb. We show a direct link between the measured optical transmission spectrum and the density-of-state of frequency crystals, validated by measurements of one-, two-, three- and four-dimensional crystals with no restrictions to further expand the dimensionality. We measure signatures of quantum random walks and Bloch oscillations in the frequency domain of light in one- and two-dimensional synthetic lattices. Our work employs a quantum description of phase modulation11 to describe resonant electro-optic frequency combs, and shows that they enable the study of exotic crystal properties, topologies and quantum dynamics, while providing a versatile platform to manipulate quantum information in the optical frequency domain.