# Manipulating quantum coherence of charge states in interacting double-dot Aharonov-Bohm interferometers

## TL;DR

This paper explores how quantum coherence of charge states in a double-dot Aharonov-Bohm interferometer can be controlled via magnetic flux and tunneling conditions, revealing a fully coherent charge qubit at resonance.

## Contribution

It demonstrates the emergence and controllability of a fully coherent charge qubit in a double-dot system with Coulomb interactions, a novel quantum state in such setups.

## Key findings

- Complete charge coherence can be achieved and controlled by magnetic flux.
- A fully coherent charge qubit appears at electron pair tunneling resonance.
- The pure quantum state can be identified at the current-voltage characteristic turnover.

## Abstract

We investigate the dynamics of charge--states coherence in a degenerate double--dot Aharonov--Bohm interferometer with finite interdot 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. Remarkably, 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 \emph{experimentally located} 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 coherences in the double--dot systems of study.