Influence of domain disorder on parametric noise in quasi-phase-matched quantum frequency converters

Ideal quantum frequency conversion (QFC) devices enable wavelength translation of a quantum state of light while preserving its essential quantum characteristics, namely photon statistics and coherence. However, the generation of noise photons due to spontaneous scattering of the strong classical pump used in the three-wave mixing process can limit QFC fidelity. We experimentally and theoretically characterize the noise properties of a difference-frequency generation device for QFC and find that fabrication errors in the quasi-phase-matching grating enhance generation of noise photons by parametric fluorescence. © 2010 Optical Society of America OCIS codes: 190.4360, 190.4975, 230.7405, 270.5565. Frequency conversion in χð2Þ media via sum- or difference-frequency generation (SFG/DFG) can inter-change the quantum states of light between two wave-lengths in a process known as quantum frequency conversion (QFC) [1]. QFC devices may assist in the de-velopment of quantum networks, in which photons are used to transfer quantum information between two nodes via a quantum channel [2], by allowing the flexibility to couple nodes operating in the visible or near-IR using tel-ecom infrastructure at 1.3 or 1:5 μm [3]. In the QFC pro-cess, an input quantum state at frequency ω1ðω2Þ can be upconverted (downconverted) to ω2ðω1Þ via a three-wave mixing process with a pump at ωp, where ω1 þ ωp ω2. If, for instance, light is input at ω2 and is being downconverted toω1, the conversion efficiency η is η ≡ hn̂1ðLÞihn̂2ð0Þi sin2 ffiffiffiffiffiffiffiffiffiffiffiffiff