Multidimensional mode-separable frequency conversion for high-speed quantum communication

TL;DR

This paper demonstrates a high-efficiency, multidimensional frequency conversion system that sorts temporal modes in quantum signals, enabling faster and more reliable quantum communication over long distances.

Contribution

It introduces the first QFC temporal mode sorting system in a four-dimensional space with high efficiency and separability, advancing quantum communication technology.

Findings

Achieved 92% conversion efficiency.

Mode separability of 0.84.

Verified mode sorting with weak coherent signals.

Abstract

Quantum frequency conversion (QFC) of photonic signals preserves quantum information while simultaneously changing the signal wavelength. A common application of QFC is to translate the wavelength of a signal compatible with the current fiber-optic infrastructure to a shorter wavelength more compatible with high quality single-photon detectors and optical memories. Recent work has investigated the use of QFC to manipulate and measure specific temporal modes (TMs) through tailoring of the pump pulses. Such a scheme holds promise for multidimensional quantum state manipulation that is both low loss and re-programmable on a fast time scale. We demonstrate the first QFC temporal mode sorting system in a four-dimensional Hilbert space, achieving a conversion efficiency and mode separability as high as 92% and 0.84, respectively. A 20-GHz pulse train is projected onto 6 different TMs, including superposition states, and mode separability with weak coherent signals is verified via photon counting. Such ultrafast high-dimensional photonic signals could enable long-distance quantum communication with high rates.