Nonclasscial interference between independent intrinsically pure single photons at telecom wavelength

We demonstrate a Hong-Ou-Mandel interference between two independent, intrinsically pure, heralded single photons from spontaneous parametric down conversion (SPDC) at telecom wavelength. A visibility of $85.5\pm8.3%$ was achieved without using any bandpass filter. Thanks to the group-velocity-matched SPDC and superconducting nanowire single photon detectors (SNSPDs), the 4-fold coincidence counts are one order higher than that in the previous experiments. The combination of bright single photon sources and SNSPDs is a crucial step for future practical quantum info-communication systems at telecom wavelength.