  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.
