  The realization of an ultra-fast source of heralded single photons emitted at
the wavelength of 1540 nm is reported. The presented strategy is based on
state-of-the-art telecom technology, combined with off-the-shelf fiber
components and waveguide non-linear stages pumped by a 10 GHz repetition rate
laser. The single photons are heralded at a rate as high as 2.1 MHz with a
heralding efficiency of 42%. Single photon character of the source is inferred
by measuring the second-order autocorrelation function. For the highest
heralding rate, a value as low as 0.023 is found. This not only proves
negligible multi-photon contributions but also represents the best measured
value reported to date for heralding rates in the MHz regime. These prime
performances, associated with a device-like configuration, are key ingredients
for both fast and secure quantum communication protocols.
