Efficient quantum frequency translation of broadband single photons by Bragg-scattering four-wave mixing

We experimentally demonstrate frequency translation of a non-classical optical field by Bragg-scattering four-wave mixing, driven by orthogonally polarized pump pulses in a birefringent optical fiber. Heralded single photons are up- and down-translated by 6.8 THz between bands at 688.1 nm and 678.2 nm, each with efficiency > 97%. The input and output spectral shape and bandwidth show negligible modulation. Second-order auto-correlation measurements of the 678.2 nm and 688.1 nm fields at maximum conversion yield values of 0.0302 ± 0.0005 and 0.028 ± 0.001, respectively, compared with the input second-order correlation of 0.026 ± 0.001; this indicates that the frequency translation process preserves the non-classical nature of the field. The high efficiency, broad bandwidth, and low noise render this scheme useful for quantum networks and sources.