  We report on two-photon interferences from highly indistinguishable single
photons emitted by a quantum dot. Stricly resonant excitation with picosecond
laser pulses allows coherent state preparation with a signifi- cantly increased
coherence time (T2 \sim 1 ns) and reduced lifetime (T1 \sim 650 ps), as
compared to a non-resonant excitation scheme. Building-up the Hong-Ou-Mandel
dip without post-selection of the interfering photons, visi- bilities greater
than 70 % have been observed. Near-unity indistinguishable photons could be
achieved for every dot if charge noise is controlled. Indeed, the remaining
decoherence mechanism is likely due to the fluctuating electrostatic
environment of the dots.
