Simulation of Coupling Strength of Capacitively Coupled Singlet-Triplet Qubits

TL;DR

This paper numerically investigates the coupling strength between two capacitively-coupled singlet-triplet qubits, revealing how it varies with qubit separation and detuning, and introduces a simplified toy model for qualitative understanding.

Contribution

It extends the Hund-Mulliken approach to include excited orbitals for more accurate simulation of interqubit coupling in singlet-triplet qubits.

Findings

Coupling strength depends on qubit separation and detuning.

A potential-independent toy model captures qualitative features.

Numerical simulations provide detailed energy structure insights.

Abstract

We consider a system of two purely capacitively-coupled singlet-triplet qubits, and numerically simulate the energy structure of four electrons in two double quantum dots with a large potential barrier between them. We calculate the interqubit coupling strength using an extended Hund-Mulliken approach which includes excited orbitals in addition to the lowest energy orbital for each quantum dot. We show the coupling strength as a function of the qubit separation, as well as plotting it against the detunings of the two double quantum dots, and show that the general qualitative features of our results can be captured by a potential-independent toy model of the system.