Influences of dispersion, dielectric constant and polarization on the double-parameter asymmetric Gaussian potential qua
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ORIGINAL PAPER
Influences of dispersion, dielectric constant and polarization on the double-parameter asymmetric Gaussian potential quantum dot qubit X-F Bai1, Y Zhang2* and Eerdunchaolu2 1
College of Engineering, Inner Mongolia University for Nationalities, Tongliao 028043, China
2
Institute of Condensed Matter Physics, Hebei Normal University of Science and Technology, Qinhuangdao 066004, China Received: 26 September 2019 / Accepted: 2 March 2020
Abstract: Selecting the double-parameter asymmetric Gaussian (AG) potential to describe the confinement effects of electrons in quantum dot (QD), the effect of dielectric constant, dispersion and polarization on the properties of the QD qubit is studied by LLP–Pekar transformation variation method. By discussing the oscillation period of the qubit with the AG potential, the mechanism of influence of the material parameters such as the dielectric constant ratio and the electron– phonon coupling (EPC) constant on qubit survival time and information storage is clarified. Based on the Fermi gold rule and the even-order approximation, the qubit decoherence with AG potential is studied. It is revealed that increasing the dielectric constant ratio, the dispersion or the EPC constant of materials is all ways to solve the qubit decoherence due to spontaneous emission of phonons. The theoretical basis for phase rotation control of qubit spheres is given by improving dispersion coefficient or dielectric constant ratio of materials. Keywords: Qubit; Asymmetric Gaussian potential; Vibration period; Decoherence time; Phase rotation quality factor
1. Introduction The basic principle of quantum computing is to use the quantized two-level system as the basic unit of information processing, and complete the complex calculation and information processing by regulating the quantum state. Quantum dot (QD) quantum computer is currently considered to be one of the most promising quantum computer solutions [1], and it is also one of the best and fastest developing solutions [2–7]. The two-level system in QDs can be used as a qubit. Among the factors that affect the storage, survival, decoherence and rotational manipulation of QD qubits, in addition to the three-dimensional confinement of electrons in QDs and electron–phonons coupling, the quality of the QDs themselves, such as dielectric constants, impurities, dispersion, etc., should also be considered. These factors are of great research value and are urgently needed to be clarified. It is important to select a suitable confinement potential function for the three-dimensional confinement of electrons in QD and electron–
*Corresponding author, E-mail: [email protected]
phonon coupling. For a long time, the single-parameter parabolic potential has been used to describe the confinement of electrons in QDs [8–12]. However, parabolic potential is an ideal model that is too simplified, and the result is undoubtedly rough. Recently, some authors [13] chose Gaussian potential function to describe the confinement of electrons in low-dimens
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