A configuration interaction analysis of exchange in double quantum dots

TL;DR

This paper introduces a comprehensive configuration interaction method for analyzing exchange interactions in double quantum dots, enabling detailed exploration of system parameters relevant to quantum computing qubits.

Contribution

The paper presents a full CI approach capable of analyzing large parameter spaces for quantum dots, surpassing limitations of previous approximate methods.

Findings

Exchange energy depends on magnetic field, detuning, dot size, and separation.

Benchmark shows CI results agree with exact solutions for two electrons.

Method is suitable for designing and optimizing quantum-dot-based qubits.

Abstract

We describe in detail a full configuration interaction (CI) method designed to analyze systems of quantum dots. This method is capable of exploring large regions of parameter space, like more approximate approaches such as Heitler London and Hund Mulliken, though it is not limited to weakly coupled dots. In particular, this method is well-suited to the analysis of solid state quantum-dot-based qubits, and we consider the case of a double quantum dot (DQD) singlet-triplet qubit. Past analyses have used techniques which are either substantially restricted in the regimes they can be used, or device specific and unsuited to exploration of a large regions of parameter space. We analyze how the DQD exchange energy, which is central to the operation of qubit rotation gates, depends on a generic set of system parameters including magnetic field, DQD detuning, dot size, and dot separation. We discuss the implications of these results to the construction of real devices. We provide a benchmark of the CI by directly comparing results from the CI method with exact results for two electrons in a single parabolic potential (dot).