Widely-tunable, spectrally pure, high efficient photon pairs generation at telecom wavelength

Photon source is one of the fundamental bricks for quantum information and computation systems. A widely-tunable, highly efficient and spectrally pure photon source would be very useful for such applications. In this paper, we present such a source based on spontaneous parametric down conversion (SPDC) in a periodically poled KTiOPO4 (PPKTP) crystal.