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

TL;DR

This study reveals how atomic-scale disorder at the Si quantum well interface affects the energy dispersion and coherence of a three-electron double-quantum-dot qubit, with implications for improving qubit fidelity.

Contribution

The paper demonstrates that atomic-scale interface disorder influences qubit behavior and can be harnessed to create decoherence-suppressing sweet spots in silicon quantum-dot qubits.

Findings

Disorder causes anomalous energy dispersion in the qubit.

Disorder profiles can induce decoherence-suppressing sweet spots.

Atomic structure can be used to enhance qubit fidelity.

Abstract

We report anomalous behavior in the energy dispersion of a three-electron double-quantum-dot hybrid qubit and argue that it is caused by atomic-scale disorder at the quantum-well interface. By employing tight-binding simulations, we identify potential disorder profiles that induce behavior consistent with the experiments. The results indicate that disorder can give rise to "sweet spots" where the decoherence caused by charge noise is suppressed, even in a parameter regime where true sweet spots are unexpected. Conversely, "hot spots" where the decoherence is enhanced can also occur. Our results suggest that, under appropriate conditions, interfacial atomic structure can be used as a tool to enhance the fidelity of Si double-dot qubits.