Light-Hole Gate-Defined Spin-Orbit Qubit

TL;DR

This paper demonstrates a light-hole spin qubit in a strained Ge quantum well with high dipole moment and tunable properties, offering a promising platform for scalable quantum networks.

Contribution

It introduces a novel light-hole qubit design with enhanced dipole moment and tunable spin properties using tensile-strained Ge quantum wells.

Findings

Light-hole qubit dipole moment is 2-3 orders of magnitude higher than heavy-hole qubits.

The qubit's g-factor and dipole moment depend on size and can be modulated.

Relaxation rate follows a B^7 dependence due to strong spin-orbit interactions.

Abstract

The selective confinement of light-holes (LHs) is demonstrated by introducing a low-dimensional system consisting of 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 2 to 3 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 $B^7$ behavior. The proposed all-group IV, direct bandgap LH qubit provides an effective platform for a scalable qubit-optical photon interface sought-after for long-range entanglement distribution and quantum networks.