Quantum Frequency Translation of Single-Photon States in a Photonic Crystal Fiber

We experimentally demonstrate frequency translation of a nonclassical optical field via four-wave mixing (Bragg-scattering process) in a photonic crystal fiber (PCF). The high nonlinearity and the ability to control dispersion in PCF enable efficient translation between nearby photon channels within the visible to-near-infrared spectral range, useful in quantum networks. Heralded single photons at 683 nm were translated to 659 nm with an efficiency of 28.6 +/- 2.2 percent. Second-order correlation measurements on the 683- and 659-nm fields yielded g(683)((2))(0) = 0.21 +/- 0.02 and g(659)((2))(0) = 0.19 +/- 0.05, respectively, showing the nonclassical nature of both fields.