Fano Effect through Parallel-coupled Double Coulomb Islands

TL;DR

This paper theoretically investigates Fano resonances in conductance spectra of parallel-coupled double quantum dots with Coulomb interactions, revealing controllable interference effects and a potential qubit swap mechanism via magnetic flux tuning.

Contribution

It introduces a detailed theoretical analysis of Fano effects in Coulomb-coupled quantum dots, highlighting the manipulation of lineshapes and a swap effect relevant for quantum computing.

Findings

Fano resonance appears in Coulomb blockade regime due to quantum interference.

Fano lineshape can be tuned by dot-lead coupling and magnetic flux.

A swap effect of quantum states is achievable through magnetic flux manipulation.

Abstract

By means of the non-equilibrium Green function and equation of motion method, the electronic transport is theoretically studied through a parallel-coupled double quantum dots(DQD) in the presence of the on-dot Coulomb correlation, with an emphasis put on the quantum interference. It has been found that in the Coulomb blockage regime, the quantum interference between the bonding and antiboding DQD states or that between their Coulomb blockade counterparts may result in the Fano resonance in the conductance spectra, and the Fano peak doublet may be observed under certain non-equilibrium condition. The possibility of manipulating the Fano lineshape is predicted by tuning the dot-lead coupling and magnetic flux threading the ring connecting the dots and leads. Similar to the case without Coulomb interaction, the direction of the asymmetric tail of Fano lineshape can be flipped by the external field. Most importantly, by tuning the magnetic flux, the function of four relevant states can be interchanged, giving rise to the swap effect, which might play a key role as a qubit in the quantum computation.