Quantum frequency downconversion experiment

TL;DR

This paper demonstrates the first successful quantum frequency downconversion of a coherent pulse train from visible to telecom wavelengths using a lithium niobate waveguide, preserving quantum phase information.

Contribution

It introduces a novel quantum frequency downconversion technique with phase preservation, enabling advanced quantum communication applications.

Findings

Achieved phase-preserved frequency downconversion from 0.7 μm to 1.3 μm.

Demonstrated compatibility with quantum networking infrastructure.

Showed potential for quantum repeater systems over optical fiber.

Abstract

We report the first quantum frequency downconversion experiment. Using the difference frequency generation process in a periodically poled lithium niobate waveguide, we successfully observed the phase-preserved frequency downconversion of a coherent pulse train with an average photon number per pulse of $<$1, from the 0.7-$\mu$m visible wavelength band to the 1.3-$\mu$m telecom band. We expect this technology to become an important tool for flexible photonic quantum networking, including the realization of quantum repeater systems over optical fiber using atom-photon entanglement sources for the visible wavelength bands.