Quantum frequency conversion (QFC) plays a critical role in practical quantum information technology as it provides a bridge among different quantum devices, which usually operate at different optimal wavelength. Photons with longer wavelength feature lower propagation loss and lower solar radiation noise in free space, hence hold promise for daylight long distance quantum communication. Besides, wavelength over 2 μ m also overlap with the absorption band of many important molecules, hence is of great importance for gases and molecules detection. Yet development of technology in this region has been hindered primarily by the spectral mismatch with other quantum devices, notably quantum detection and memories, which optimally operate in the visible band. Here, we demonstrate the first QFC of 2 μ m photons to the visible region on domain-engineered thin-film lithium niobate (TFLN) platform. Benefiting from the strong nonlinearity in such integrated platform, the highest internal quantum conversion efficiency of 42% is achieved at an exceptionally low pump saturation power of only 58 mW . This work provides an efficient interconnection between photons operating at the visible and 2 μ m bands in the integrated platform, pushing forward the development of practical quantum chips for application of quantum communication, sensing and metrology in the future. • Strong mode confinement and domain-engineered thin film lithium niobate (TFLN), combined with large χ ( 2 ) , enable efficient on-chip nonlinear conversion. • First demonstration of quantum frequency conversion (QFC) of 2 μ m band photon on thin film lithium niobate.
Gu et al. (Thu,) studied this question.