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Physical Review B

Inversion recovery of single quantum-dot exciton based qubit

Roman S. Kolodka, A. J. Ramsay, J. Skiba-Szymanska, P. W. Fry, Huiyun Liu, A. M. Fox, Maurice S. Skolnick

Published May 10, 2007• 34 citations
Publisher

Abstract

We investigate the coherence decay of a single-exciton-based qubit with electrical readout. Pairs of laser pulses initialize the qubit state and then map the target basis onto the measurement basis, probing the decay of either the population inversion or electronic polarization components of the state vector. A comparison of coherence and population decay confirms that the exciton coherence is lifetime limited by fast voltage-tunable electron tunneling. Optimum coherence times are limited by a heavy-hole tunneling rate slow compared with the repetition rate of the laser.

DOI
10.1103/physrevb.75.193306

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We report on coherent control of the fundamental exciton state in a single quantum dot by means of two phase-locked picosecond laser pulses. By analyzing the experiments performed in the Rabi regime and comparing them to numerical simulations, we show that we can address the exciton coherence and get an insight into the involved dephasing processes. The total decoherence time T2{T}_{2}T2​ (170 ps) is comparable to the effective exciton lifetime T1{T}_{1}T1​ (200 ps), although not reaching the upper theoretical limit of 2T12{T}_{1}2T1​. We conclude that energy relaxation and pure dephasing processes due to virtual scattering with phonons both contribute on an equal footing to the loss of coherence in this kind of monolayer-step-induced GaAs quantum dots.