Electronic states of InAs vertically-assembled quantum disks in magnetic fields and two-electron quantum-disk qubit

We have studied the single-electron and two-electron vertically-assembled quantum disks in an axial magnetic field using the effective mass approximation. The electron interaction is treated accurately by the direct diagonalization of the Hamiltonian matrix. We calculate the six energy levels of single-electron quantum disks and the two lowest energy levels of two-electron quantum disks in an axial magnetic field. The change of the magnetic field as an effective potential strongly modifies the electronic structures, leading to splittings and crossings between levels. The results demonstrate the switching between the ground slates with the total spins S=0 and S = 1. The switching results in a qubit allowed fabricating by current growth techniques.