# Quantum interference in transport through almost symmetric double quantum dots

## TL;DR

This paper explores how quantum interference affects electron transport in nearly symmetric double quantum dots, revealing that tiny symmetry-breaking effects can significantly alter current flow, enabling ultra-sensitive electric switching.

## Contribution

It introduces a theoretical framework using a master equation with quantum interference effects and shows how small symmetry-breaking perturbations influence stationary states and current levels.

## Key findings

- Weak symmetry-breaking dramatically impacts current.
- Symmetry-breaking stabilizes different stationary states.
- Double quantum dots can serve as sensitive electric switches.

## Abstract

We theoretically investigate transport signatures of quantum interference in highly symmetric double quantum dots in a parallel geometry and demonstrate that extremely weak symmetry-breaking effects can have a dramatic influence on the current. Our calculations are based on a master equation where quantum interference enters as non-diagonal elements of the density matrix of the double quantum dots. We also show that many results have a physically intuitive meaning when recasting our equations as Bloch-like equations for a pseudo spin associated with the dot occupation. In the perfectly symmetric configuration with equal tunnel couplings and orbital energies of both dots, there is no unique stationary state density matrix. Interestingly, however, adding arbitrarily small symmetry-breaking terms to the tunnel couplings or orbital energies stabilizes a stationary state either with or without quantum interference, depending on the competition between these two perturbations. The different solutions can correspond to very different current levels. Therefore, if the orbital energies and/or tunnel couplings are controlled by, e.g., electrostatic gating, the double quantum dot can act as an exceptionally sensitive electric switch.