Pure dephasing of double-quantum-dot charge qubits in freestanding slabs

Abstract

slab. Density matrix is used to analyze the dynamics of the qubit. By calculating the pure dephasing factor, our results show that the characteristics of phonon modes strongly affect the evolution of the qubit. Because of the confinement, the factor obviously reveals an oscillatory behavior. The effect of individual phonon modes is presented in detail in this research. We also analyze the dependence of temperature on the factor. Moreover, two distinct tendencies are obtained due to particular phonon characteristics. A double-dot charge qubit is placed in a freestanding semiconductor slab, as shown in Fig. 1. The double-dot structure can be engineered with the help of the external gates. 28,31 The parameters of confinement potential, such as its magnitude and profile, are precisely modulated via gate voltages. 5 The confinement configuration can be stably kept under the control of the gates. Most parts of the slab structure are spatially isolated from the support substrate. The in-plane scale of the slab is assumed to exceed substantially the width w and dot radius a. This state ensures that the effect in contact with the substrate can be neglected in the system. The quantum dots are horizontally arranged along the x-axis direction and located at the position z0 from the center of the slab. To define the logical states of the qubit, we assume that only an additional electron is allowed to exist on the DQD, i.e., an excess electron occupies either the left dot L or the right dot R. 3,33 The total Hamiltonian of the system is z