Suppression of exciton dephasing in quantum dots through ultrafast multipulse control

TL;DR

This paper demonstrates that applying ultrafast multipulse control sequences can significantly reduce exciton dephasing in quantum dots, enhancing their potential for quantum computing by improving coherence times.

Contribution

It shows that dynamical decoupling via periodic pulses effectively suppresses phonon-induced dephasing in exciton qubits within quantum dots, especially those optimized for quantum computation.

Findings

Periodic control pulses improve exciton coherence times.

Quantum dot shape influences dephasing and control efficiency.

Electric fields can enhance dynamical decoupling effectiveness.

Abstract

We investigate the usefulness and viability of the scheme developed by Viola and Lloyd [Phys. Rev. A 58, 2733 (1998)] to control dephasing in the context of exciton-based quantum computation with self-assembled quantum dots. We demonstrate that optical coherence of a confined exciton qubit exposed to phonon-induced dephasing can be substantially enhanced through the application of a simple periodic sequence of control pulses. The shape of the quantum dot has a significant effect on the dephasing properties. Remarkably, we find that quantum dots with parameters optimized for implementing quantum computation are among the most susceptible to dephasing, yet periodic decoupling is most efficient for exactly that type of dot. We also show that the presence of an electric field, which is a necessary ingredient for many exciton-based quantum computing schemes, may further increase the control efficiency. Our results suggest that dynamical decoupling may be a method of choice for robust storage of exciton qubits during idle stages of quantum algorithms.