Storage of up-converted telecom photons in a doped crystal

Abstract

We report on an experiment that demonstrates the frequency up-conversion of telecommunication wavelength single-photon-level pulses to be resonant with a ${{{\rm Pr} }^{3+}}$ : ${{{\rm Y}}_{2}}{\rm Si}{{{\rm O}}_{5}}$ crystal. We convert the telecom photons at $1570\;{\rm nm}$ to $606\;{\rm nm}$ using a periodically-poled potassium titanyl phosphate nonlinear waveguide. The maximum device efficiency (which includes all optical loss) is inferred to be $\eta _{{\rm dev}}^{{\rm max} }=22\pm 1\%$ (internal efficiency ${{\eta }_{\operatorname{int}}}=75\pm 8\%$ ) with a signal to noise ratio exceeding 1 for single-photon-level pulses with durations of up to 560 ns. The converted light is then stored in the crystal using the atomic frequency comb scheme with storage and retrieval efficiencies exceeding ${{\eta }_{{\rm AFC}}}=20\%$ for predetermined storage times of up to $5\;\mu {\rm s}$ . The retrieved light is time delayed from the noisy conversion process allowing us to measure a signal to noise ratio exceeding 100 with telecom single-photon-level inputs. These results represent the first demonstration of single-photon-level optical storage interfaced with frequency up-conversion.

Keywords

• quantum information
• quantum memory
• nonlinear waveguides
• 03.67.Hk
• 42.50.Gy
• 42.50.Md