Charge-noise resilience of two-electron quantum dots in Si/SiGe heterostructures

TL;DR

This paper investigates charge-noise resilience in two-electron silicon quantum dots, revealing that valley-excited triplet states naturally offer protection against charge noise, especially in strongly confined dots, highlighting an advantage for silicon qubits.

Contribution

It demonstrates that valley-excited triplet states in silicon quantum dots provide inherent charge-noise protection, a novel insight for silicon-based qubit design.

Findings

Valley-excited triplet states are present in typical operating regimes.

Only valley triplets offer intrinsic charge-noise protection.

Stronger confinement enhances this protection.

Abstract

The valley degree of freedom presents challenges and opportunities for silicon spin qubits. An important consideration for singlet-triplet states is the presence of two distinct triplets, comprised of valley vs. orbital excitations. Here we show that both of these triplets are present in the typical operating regime, but that only the valley-excited triplet offers intrinsic protection against charge noise. We further show that this protection arises naturally in dots with stronger confinement. These results reveal an inherent advantage for silicon-based multi-electron qubits.