Signatures of atomic-scale structure in the energy dispersion and coherence of a Si quantum-dot qubit

Abstract

Valley splitting affects the energy dispersion of silicon quantum dot qubits, and occasionally manifests itself through some striking features. Here, the authors observe a strong correlation between unexpected ``sweet spots'' and ``hot spots'' in the coherence rates of a quantum-dot hybrid qubit and in some anomalous features in the energy dispersion. Through tight-binding simulations, they are able to attribute such effects to disorder at the quantum-well interface and speculate on the possibility of harnessing disorder to enhance qubit coherence times.