Abstract
We investigate the dynamics of charge-state coherence in a degenerate double-dot Aharonov–Bohm interferometer with finite inter-dot Coulomb interactions. The quantum coherence of the charge states is found to be sensitive to the transport setup configurations, involving both the single-electron impurity channels and the Coulomb-assisted ones. We numerically demonstrate the emergence of a complete coherence between the two charge states, with the relative phase being continuously controllable through the magnetic flux. Interestingly, a fully coherent charge qubit arises at the double-dots electron pair tunneling resonance condition, where the chemical potential of one electrode is tuned at the center between a single-electron impurity channel and the related Coulomb-assisted channel. This pure quantum state of charge qubit could be experimentally realized at the current–voltage characteristic turnover position, where differential conductance sign changes. We further elaborate the underlying mechanism for both the real-time and the stationary charge-states coherence in the double-dot systems of study.
Highlights
The investigations of semiconductor quantum dots have long aroused a great deal of attentions
We investigate the dynamics of charge–states coherence in a degenerate double–dot Aharonov– Bohm interferometer with finite interdot Coulomb interactions
We numerically demonstrate the emergence of a complete coherence between the two charge states, with the relative phase being continuously controllable through the magnetic flux
Summary
The investigations of semiconductor quantum dots have long aroused a great deal of attentions. The resulted coherent transport property has been characterized via conductance oscillation in magnetic flux.[12,13] It has been widely studied in quantum transport the relation of the coherence of AB oscillations to Coulomb interaction,[16–22] interdot tunneling,[14,21] and inelastic electron cotunneling processes,[13,25] etc. A fully coherent charge qubit emerges at the double–dots electron pair tunneling resonance, when the chemical potential of one electrode matches with the center between a single–electron impurity channel and the related Coulomb channel. This pure quantum state of charge quit could be experimentally located at the current–voltage characteristic turnover position, where differential conductance changes sign, from negative (positive) to positive (negative).
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