Nonequilibrium stabilization of charge states in double quantum dots

TL;DR

This paper investigates how nonequilibrium conditions can be used to enhance the coherence times of charge states in double quantum dots, with implications for quantum computing applications.

Contribution

It demonstrates that decoherence times can be maximized under nonequilibrium conditions, challenging the assumption that equilibrium states are optimal for coherence.

Findings

Decoherence times are controllable via external voltage.

Maximum coherence occurs out of equilibrium.

The mechanism involves nonequilibrium-induced lifetime enhancement.

Abstract

We analyze the decoherence of charge states in double quantum dots due to cotunneling. The system is treated using the Bloch-Redfield generalized master equation for the Schrieffer-Wolff transformed Hamiltonian. We show that the decoherence, characterized through a relaxation $\tau_{r}$ and a dephasing time $\tau_{\phi}$, can be controlled through the external voltage and that the optimum point, where these times are maximum, is not necessarily in equilibrium. We outline the mechanism of this nonequilibrium-induced enhancement of lifetime and coherence. We discuss the relevance of our results for recent charge qubit experiments.