Spin qubits in germanium gate-defined quantum dots have made considerable progress within the last few years, partially due to their strong spin-orbit coupling and site-dependent g-tensors.
While this characteristic of the g-factors removes the need for micromagnets and allows for the possibility of all-electric qubit control, relying on these g-tensors necessitates the need to understand their sensitivity to the confinement potential that defines the quantum dots.
Researchers have demonstrated a S − T_ qubit whose frequency is a strong function of the voltage applied to the barrier gate shared by the quantum dots.
They found a g-factor that can be approximately increased by an order of magnitude adjusting the barrier gate voltage only by 12 mV. They showed how this strong dependence could potentially be attributed to the dots moving through a variable strain environment in our device. T
his work not only reinforces previous findings that site-dependent g-tensors in germanium can be utilized for qubit manipulation, but reveals the sensitivity and tunability these g-tensors have to the electrostatic confinement of the quantum dot.
npj Quantum Information, Published online: 29 January 2025; doi:10.1038/s41534-024-00953-3