Photon Conversion in Thin-film Lithium Niobate Nanowaveguides: A Noise Analysis

TL;DR

This paper investigates quantum noise in lithium niobate nanowaveguides during wavelength conversion, revealing low noise levels suitable for quantum networks and providing a formula for noise suppression.

Contribution

First study of quantum noise in lithium niobate nanowaveguides during telecom to near-visible conversion, with analysis and noise suppression formula.

Findings

Noise level around 10^{-4} photons per mode at high conversion

Noise suppression achievable to 10^{-5} photons per mode

Low-cost, scalable approach for quantum network applications

Abstract

Wavelength transduction of single-photon signals is indispensable to networked quantum applications, particularly those incorporating quantum memories. Lithium niobate nanophotonic devices have demonstrated favorable linear, nonlinear, and electro-optical properties to deliver this crucial function while offering superiror efficiency, integrability, and scalability. Yet, their quantum noise level--an crucial metric for any single-photon based application--has yet to be understood. In this work, we report the first study with the focus on telecom to near-visible conversion driven by a telecom pump of small detuning, for practical considerations in distributed quantum processing over fiber networks. Our results find the noise level to be on the order of $10^{-4}$ photons per time-frequency mode for high conversion, allowing faithful pulsed operations. Through carefully analyzing the origins of such noise and each's dependence on the pump power and wavelength detuning, we have also identified a formula for noise suppression to $10^{-5}$ photons per mode. Our results assert a viable, low-cost, and modular approach to networked quantum processing and beyond using lithium niobate nanophotonics.