Abstract
Unexpected fluctuating charge field near a semiconductor quantum dot has severely limited the coherence time of the localized spin qubit. It is the interplay between the spin–orbit coupling and the asymmetrical confining potential in a quantum dot, that mediates the longitudinal interaction between the spin qubit and the fluctuating charge field. Here, we study the 1/f charge noise induced spin dephasing in a nanowire double quantum dot via exactly solving its eigen-energies and eigenfunctions. Our calculations demonstrate that the spin dephasing has a nonmonotonic dependence on the asymmetry of the double quantum dot confining potential. With the increase of the potential asymmetry, the dephasing rate first becomes stronger very sharply before reaching to a maximum, after that it becomes weaker softly. Also, we find that the applied external magnetic field contributes to the spin dephasing, the dephasing rate is strongest at the anti-crossing point B0 in the double quantum dot.
Highlights
The coherence of a quantum bit, an interesting phenomenon originating from the superposition of quantum states in quantum mechanics, has many applications in quantum computing and quantum information processing [1, 2]
Unexpected fluctuating charge field near a semiconductor quantum dot has severely limited the coherence time of the localized spin qubit. It is the interplay between the spin-orbit coupling and the asymmetrical confining potential in a quantum dot, that mediates the longitudinal interaction between the spin qubit and the fluctuating charge field
Our calculations demonstrate that the spin dephasing has a nonmonotonic dependence on the asymmetry of the double quantum dot confining potential
Summary
The coherence of a quantum bit (qubit), an interesting phenomenon originating from the superposition of quantum states in quantum mechanics, has many applications in quantum computing and quantum information processing [1, 2]. We find that a little asymmetry in the DQD confining potential, e.g., several fractions of a milli-electron-volt (meV) in the potential difference or several nanometers (nm) in the width difference between the left and the right dots of the DQD, can give rise to a remarkable spin dephasing. This would be instructive and meaningful to the quantum computing architecture based on semiconductor quantum dot, because it is almost impossible to produce an exactly symmetrical quantum dot confining potential in experiments.
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