InAs/GaAs single-electron quantum dot qubit

TLDR

The study models electron dynamics in InAs/GaAs quantum dots using effective‑mass envelope function theory, computes inter‑dot Coulomb interactions for electrons in pure states, and maps a parameter‑phase diagram delineating the two‑level regime for quantum computation. Electron density in the dot oscillates with femtosecond periods, inter‑dot interaction energies satisfy E11 > E12 > E22 and decay with distance, a static electric field extends decoherence time, and these insights aid solid‑state quantum computing design.

Abstract

The time evolution of the quantum mechanical state of an electron is calculated in the framework of the effective-mass envelope function theory for an InAs/GaAs quantum dot. The results indicate that the superposition state electron density oscillates in the quantum dot, with a period on the order of femtoseconds. The interaction energy Eij between two electrons located in different quantum dots is calculated for one electron in the ith pure quantum state and another in the jth pure quantum state. We find that E11〉E12〉E22, and Eij decreases as the distance between the two quantum dots increases. We present a parameter-phase diagram which defines the parameter region for the use of an InAs/GaAs quantum dot as a two-level quantum system in quantum computation. A static electric field is found to efficiently prolong the decoherence time. Our results should be useful for designing the solid-state implementation of quantum computing.