We demonstrate upconversion-assisted single-photon detection for the 1.55-μm telecommunications band based on a periodically poled lithium niobate (PPLN) waveguide pumped by a monolithic PPLN optical parametric oscillator. We achieve an internal conversion efficiency of 86%, which results in an overall system detection efficiency of 37%, with excess noise as low as 10(3) counts s(-1). We measure the dark count rate versus the upconversion pump-signal frequency separation and find the results to be consistent with noise photon generation by spontaneous anti-Stokes Raman scattering. These results enable detailed design guidelines for the development of low-noise quantum frequency conversion systems, which will be an important component of fiber-optic quantum networks.

The ability to transduce non-classical states of light from one wavelength to another is a requirement for integrating disparate quantum systems that take advantage of telecommunications-band photons for optical fiber transmission of quantum information and near-visible, stationary systems for manipulation and storage. In addition, transducing a single-photon source at 1.3 µm to visible wavelengths for detection would be integral to linear optical quantum computation due to the challenges of detection in the nearinfrared. Recently, transduction at single-photon power levels has been accomplished through frequency upconversion, but it has yet to be demonstrated for a true single-photon source. Here, we transduce the triggered single-photon emission of a semiconductor quantum dot at 1.3 µm to 710 nm with a total detection (internal conversion) efficiency of 21 % (75 %). We demonstrate that the 710 nm signal maintains the quantum character of the 1.3 µm signal, yielding a photon anti-bunched second-order intensity correlation, g (2) (τ), that shows the optical field is composed of single photons with g (2) (0) = 0.165 < 0.5.

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