Tunable singlet-triplet splitting in a few-electron Si/SiGe quantum dot

TL;DR

This paper investigates the excited-state spectrum of a Si/SiGe quantum dot, demonstrating that the singlet-triplet splitting can be tuned via lateral displacement, with implications for spin qubit control.

Contribution

It provides the first measurement of tunable singlet-triplet splitting in a Si/SiGe quantum dot through gate voltage manipulation.

Findings

Singlet-triplet splitting is tunable by lateral dot displacement.

The spectrum includes a valley-orbit excited state.

Data aligns with theoretical valley-orbit state models.

Abstract

We measure the excited-state spectrum of a Si/SiGe quantum dot as a function of in-plane magnetic field, and we identify the spin of the lowest three eigenstates in an effective two-electron regime. The singlet-triplet splitting is an essential parameter describing spin qubits, and we extract this splitting from the data. We find it to be tunable by lateral displacement of the dot, which is realized by changing two gate voltages on opposite sides of the device. We present calculations showing the data are consistent with a spectrum in which the first excited state of the dot is a valley-orbit state.