Dispersive readout of valley splittings in cavity-coupled silicon quantum dots

TL;DR

This paper introduces a cavity-based method to accurately measure valley splittings in silicon quantum dots, providing a new way to probe microscopic energy structures relevant for quantum computing.

Contribution

It presents a novel dispersive readout technique using microwave resonators to detect valley splittings in Si/SiGe quantum dots, revealing detailed energy level information.

Findings

Observable cavity transmission features correlate with valley states

Fingerprint of energy level structure obtained from cavity signals

Method enables precise measurement of valley splittings

Abstract

The bandstructure of bulk silicon has a six-fold valley degeneracy. Strain in the Si/SiGe quantum well system partially lifts the valley degeneracy, but the materials factors that set the splitting of the two lowest lying valleys are still under intense investigation. We propose a method for accurately determining the valley splitting in Si/SiGe double quantum dots embedded into a superconducting microwave resonator. We show that low lying valley states in the double quantum dot energy level spectrum lead to readily observable features in the cavity transmission. These features generate a "fingerprint" of the microscopic energy level structure of a semiconductor double quantum dot, providing useful information on valley splittings and intervalley coupling rates.