Decoherence of a resonantly driven exciton in a single quantum dot

Abstract

We report on coherent control of the resonantly driven exciton state in a single quantum dot in the strong coupling regime. With picosecond laser pulses, the two-level system undergoes Rabi oscillations and a given coherent superposition of states can be addressed. Using a pair of phase-locked pulses, optical manipulation is achieved during the coherence time of the qu-bit. The dephasing processes are also studied and we show that in typical quantum dots, the coherence time T2 can be of the same order of magnitude as the effective lifetime of the exciton T1 (a few hundreds of ps) although not reaching the upper theoretical limit of 2T1. We conclude that energy relaxation and pure dephasing processes due to virtual scattering with phonons contribute on an equal footing to the loss of coherence. © 2010 IOP Publishing Ltd.