Light-hole gate-defined spin-orbit qubit

The selective confinement of light holes (LHs) is demonstrated by introducing a low-dimensional system consisting of a highly tensile-strained Ge quantum well enabling the design of an ultrafast gate-defined spin qubit under the electric dipole spin resonance. The qubit size-dependent g factor and dipole moment are mapped, and the parameters inducing their modulation are discussed. It is found that the LH qubit dipole moment is two to three orders of magnitude higher than that of the canonical heavy-hole qubit. This behavior originates from the significant spin splitting resulting from the combined action of large cubic and linear Rashba spin-orbit interactions that are peculiar to LHs. The qubit relaxation rate is also affected by the strong spin-orbit interaction and follows typically a B7 behavior. The proposed all-group IV, direct band-gap LH qubit provides an effective platform for a scalable qubit-optical photon interface sought after for long-range entanglement distribution and quantum networks.