Qubit ZooDescription
Hole spin qubits encode quantum information in valence-band hole spins confined in semiconductor quantum dots (commonly Ge/SiGe). Strong spin-orbit coupling enables all-electric qubit control (EDSR) without requiring micromagnets, enabling faster gate operations and easier scaling of control wiring.
The tradeoff is stronger coupling to electrical noise compared with electron-spin qubits, which can limit coherence unless careful sweet-spot design and materials engineering are used.
Figure
Hamiltonian
Effective single-qubit model:
where the second term is spin-orbit-mediated electric driving. Two-qubit coupling is typically exchange:
Motivation
Hole-spin platforms are attractive because spin-orbit coupling turns electric fields into effective spin-control channels, eliminating some of the microwave magnetic-field infrastructure needed for electron-spin ESR control. This supports dense integration and fast gate operations in semiconductor-compatible processes.
Key Findings
- Ge/SiGe hole-spin qubits demonstrate fast all-electric control.
- Strong spin-orbit coupling enables high Rabi frequencies at modest drive power.
- Device design can trade speed for coherence by tuning confinement and field orientation.
- Two-qubit exchange gates are compatible with existing semiconductor control stacks.
Key Metrics
| Metric | Value | Notes | Fidelity reference |
|---|---|---|---|
| 1Q gate time | 1–50 ns | Fast EDSR control | — |
| 1Q fidelity | 99–99.9% | Rapid progress in Ge devices | Hendrickx et al. 2021 |
| 2Q fidelity | 98–99.5% | Exchange-based | Hendrickx et al. 2021 |
| 1–20 μs | Device/material dependent | — | |
| Operating temperature | 20 mK – 1 K | Some hot-qubit demonstrations | — |