We probe the indistinguishability of photons emitted by a semiconductor quantum dot (QD) via time- and temperature- dependent two-photon interference (TPI) experiments. An increase in temporal-separation between consecutive photon emission events, re
veals a decrease in TPI visibility on a nanosecond timescale, theoretically described by a non-Markovian noise process in agreement with fluctuating charge-traps in the QDs vicinity. Phonon-induced pure dephasing results in a decrease in TPI visibility from $(96pm4),$% at 10,K to a vanishing visibility at 40,K. In contrast to Michelson-type measurements, our experiments provide direct access to the time-dependent coherence of a quantum emitter at a nanosecond timescale.
