Decoherence suppression of excitons in semiconductor using sequential femtosecond pulses

Geometrical phases of excitonic qubits in quantum dots

“…Figures 4(a) and (b) show that the non-unitary contributions due to phonon mediated interactions (as quantified by η c ) increases with pulse interval t. This is due to more time available for decoherence effects at larger values of t. It is notable that decoherence due to thermal effects decreases significantly for t ∼ 0.1 ps at bath temperatures as high as 120 K. The dynamic decoupling mechanism provided by the π-pulses are just as effective in reducing decoherence associated with zero point fluctuations in the lattice medium. Overall the figure illustrates the fact that as the pulse interval becomes smaller, the effectiveness of the pulse control increases which is consistent with results of earlier works [31,35,44].…”

“…We consider the case of an excitonic qubit that is subjected to two successive optical π pulses of femtosecond duration [35]. The first π-pulse rotates the qubit state vector through an angle π about the x-axis while the second pulse inverts the state vector back to its initial state.…”

“…We assume that the important effect of reversal of time evolution of the qubit system is achieved during the bit-flipping of qubit vectors. This is justified for pulses of very short duration which is of the same order of magnitude as phonon interaction and decay times in the non-Markovian dynamics regime [35]. To simplify the model, we ignore exciton-phonon interaction while the decoupling pulses are switched on.…”

“…One of the first experimental works on πpulsing of excitons [35] has recently confirmed that ultrashort π pulse sequences can control and decrease decoherence effects. In our work, we specifically examine the effect of dynamical decoupling [35,36] on the evolution of geometrical phases during the first cycle of π-pulsing. There has been relatively little focus in the literature on the effect of decoherence on geometrical phases during π-pulsing of twolevel quantum systems.…”

“…The decoherence of excitonic system in semiconductors is generally investigated by the four-wave and six-wave mixing techniques [34]. One of the first experimental works on πpulsing of excitons [35] has recently confirmed that ultrashort π pulse sequences can control and decrease decoherence effects. In our work, we specifically examine the effect of dynamical decoupling [35,36] on the evolution of geometrical phases during the first cycle of π-pulsing.…”