Determine the spin–orbit and valley–orbit mixing that limits qubit coherence

Determine the strength and character of the spin–orbit and valley–orbit mixing mechanisms that limit coherence in bilayer-graphene spin, valley, and spin–valley qubits, so that quantitative predictions based on measured charge noise can be obtained.

Background

The measured charge noise can be used to estimate coherence limits for charge qubits, but the same quantitative analysis does not directly apply to spin and valley qubits because charge noise couples to their energies indirectly through spin–orbit and valley–orbit mixing. The relevant mixing strength and character determine how strongly charge fluctuations affect these qubits. The paper leaves these quantities unresolved and therefore cannot provide quantitative charge-noise-based coherence predictions for the spin- and valley-related qubits.