A reconfigurable silicon photonics chip for the generation of frequency bin entangled qudits

TL;DR

This paper introduces a reconfigurable silicon photonics chip capable of generating high-dimensional frequency bin entangled qudits with adjustable parameters, enabling advanced quantum communication applications.

Contribution

The authors develop a programmable silicon photonics device that can reconfigure bin spacing, qudit dimension, and quantum states on-chip, surpassing limitations of single resonator systems.

Findings

Achieved high brightness with MHz/(mW)^2 per comb line

Generated entangled states with fidelities above 85% for Bell states up to 16 dimensions

Measured fidelities exceeding 98% for two-qubit and two-qutrit states

Abstract

Quantum optical microcombs in integrated ring resonators generate entangled photon pairs over many spectral modes, and allow the preparation of high dimensional qudit states. Ideally, those sources should be programmable and have a high generation rate, with comb lines tightly spaced for the implementation of efficient qudit gates based on electro-optic frequency mixing. While these requirements cannot all be satisfied by a single resonator device, for which there is a trade-off between high generation rate and tight bin spacing, a promising strategy is the use of multiple resonators, each generating photon pairs in specific frequency bins via spontaneous four-wave mixing. Based on this approach we present a programmable silicon photonics device for the generation of frequency bin entangled qudits, in which bin spacing, qudit dimension, and bipartite quantum state can be reconfigured on-chip. Using resonators with a radius of 22 microns, we achieve a high brightness (MHz/(mW)^2) per comb line with a bin spacing of 15 GHz, and fidelities above 85% with maximally entangled Bell states up to a Hilbert space dimension of sixteen. By individually addressing each spectral mode, we realize states that can not be generated on-chip using a single resonator. We measure the correlation matrices of maximally entangled two-qubit and two-qutrit states on a set of mutually unbiased bases, finding fidelities exceeding 98%, and indicating that the source can find application in high-dimensional secure communication protocols.