Hybrid quantum networks will be based on nodes that operate at different wavelengths, requiring quantum channel standardization via quantum frequency conversion (QFC). QFC is typically based on highly efficient sum- or difference-frequency generation in second-order nonlinear materials, such as periodically poled lithium niobate waveguides. The presence of the strong pump beam in such a nonlinear medium leads to unwanted nonlinear processes that produce noise. One of these noise processes is spontaneous Raman scattering (SRS). Typically, the pump is chosen to be the longest wavelength in the second-order nonlinear mixing process so that noise photons at the signal wavelength are produced by the less efficient anti-Stokes Raman scattering process rather than the Stokes scattering process. Since SRS is a temperature-dependent process, lowering the temperature reduces the Raman-scattered photons. We discuss the theory of temperature-dependent Raman scattering and present experimental results of the temperature dependence of dark count rates in a guided-wave QFC device.

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Paulina S. Kuo, Carsten Langrock, Jason S. Pelc, and Martin M. Fejer, "Temperature dependent noise in quantum frequency conversion (Conference Presentation)," Proc. SPIE 10684, Nonlinear Optics and its Applications 2018, 1068413 (Presented at SPIE Photonics Europe: April 25, 2018; Published: 23 May 2018); https://doi.org/10.1117/12.2305978.5788846712001.