Deterministic and Universal Frequency-Bin Gate for High-Dimensional Quantum Technologies

TL;DR

This paper introduces a deterministic, high-fidelity, programmable frequency-bin quantum gate for high-dimensional photonic systems, enabling scalable quantum information processing with current and future technology.

Contribution

It presents a novel cavity-assisted sum-frequency-generation device that implements scalable, universal unitary transformations on frequency-bin modes, advancing high-dimensional quantum computing capabilities.

Findings

Achieves near-unity fidelity in frequency-bin quantum gates.

Supports high-dimensional transformations up to 10^4 modes.

Compatible with existing quantum sources and detectors for scalable processing.

Abstract

High-dimensional photonic systems access large Hilbert spaces for quantum information processing. They offer proven advantages in quantum computation, communication, and sensing. However, implementing scalable, low-loss unitary gates across many modes remains a central challenge. Here we propose a deterministic, universal, and fully programmable high-dimensional quantum gate based on a cavity-assisted sum-frequency-generation process, achieving near-unity fidelity. The device implements an M-by-N truncated unitary transformation (with 1 <= M < N), or a full unitary when M = N, on frequency-bin modes. With current technology, the attainable dimensionality reaches M-by-N on the order of ten to the power of four, with N up to about one thousand, and can be further increased using multiple pulse shapers. Combined with compatible SPDC sources, high-efficiency detection, and fast feed-forward, this approach provides a scalable, fiber-compatible platform for high-dimensional frequency-bin quantum processing.