Fig. 3
Characterization of the quantum frequency converter. a The external conversion efficiency of the two interferometer arms depending on the pump power of the mixing field at 2456 nm. The data points are fitted with \(\eta _{{\mathrm{ext}}}\left( {P_{\mathrm{P}}} \right)\) = \(\eta _{{\mathrm{max}}}{\mathrm{sin}}^2\left( {\sqrt {\eta _{{\mathrm{nor}}}P_{\mathrm{P}}} L} \right)\)39. b The absolute values of the process matrix of the coherent polarization-preserving down-conversion measured with a laser. The process fidelity is determined by the element corresponding to the identity operation (red bar). We achieve a value of 99.75 ± 0.18%. The error bars are deduced from a Poissonian distribution
