An extremely low-noise heralded single-photon source without temporal post-selection

With the recent progresses in quantum technologies, single photon sources have gained a primary relevance. Herewe present a heralded single photon source characterized by an extremely low level of noise photons, realizedby exploiting low-jitter electronics and detectors and fast custom-made electronics used to control an opticalshutter (a LiNbO 3 waveguide optical switch) at the output of the source. This single photon source showed asecond-order autocorrelation function g (2) (0) = 0: 005(7), and an Output Noise Factor (de ned as the ratio ofnoise photons to total photons at the source output) of 0 :25(1)%, among the best ever achieved.Keywords: quantum technologies, quantum information, quantum optics, single photon sources. 1. INTRODUCTION Many applicative and fundamental research elds such as quantum information, 1{3 quantum metrology, 4{8 andquantum mechanics foundations investigation 9{12 nd a fundamental tool in single photon sources, and as aconsequence there is much interest and e ort in improving their performances.