A high-dimensional quantum frequency converter

TL;DR

This paper introduces a novel high-dimensional quantum frequency converter capable of converting complex quantum states like qudits, demonstrated through high-fidelity infrared to visible conversions, advancing quantum communication networks.

Contribution

It presents the first high-dimensional quantum frequency converter for orbital angular momentum qudits, enabling high-fidelity state conversion in multiple dimensions.

Findings

Achieved high fidelities up to 98.29% for 2D qudits.

Successfully converted qudits from infrared to visible range.

Demonstrated potential for high-capacity quantum communication.

Abstract

In high dimensional quantum communication networks, quantum frequency convertor (QFC) is indispensable as an interface in the frequency domain. For example, many QFCs have been built to link atomic memories and fiber channels. However, almost all of QFCs work in a two-dimensional space. It is still a pivotal challenge to construct a high-quality QFC for some complex quantum states, e.g., a high dimensional single-photon state that refers to a qudit. Here, we firstly propose a high-dimensional QFC for an orbital angular momentum qudit via sum frequency conversion with a flat top beam pump. As a proof-of-principle demonstration, we realize quantum frequency conversions for a qudit from infrared to visible range. Based on the qudit quantum state tomography, the fidelities of converted state are 98.29(95.02)\%, 97.42(91.74)\%, and 86.75(67.04)\% for a qudit without (with) dark counts in 2,3, and 5 dimensions, respectively. The demonstration is very promising for constructing a high capacity quantum communication network.