Ge hole spin qubit

Abstract: Holes confined in quantum dots have gained considerable interest in the past few years due to their potential as spin qubits. Here we demonstrate double quantum dot devices in Ge hut wires. Low temperature transport measurements reveal Pauli spin blockade. We demonstrate electric-dipole spin resonance by applying a radio frequency electric field to one of the electrodes defining the double quantum dot. Next, we induce coherent hole spin oscillations by varying the duration of the microwave burst. Rabi oscillations with frequencies reaching 140MHz are observed. Finally, Ramsey experiments reveal dephasing times of 130ns. The reported results emphasize the potential of Ge as a platform for fast and scalable hole spin qubit devices.

Insights into Ge Hole Spin Qubits: Experimental Advancements and Implications

The research presented in the paper demonstrates significant progress in the utilization of germanium (Ge) hole spin qubits, specifically within double quantum dot (DQD) devices fabricated in Ge hut wires. At the core of this study is the implementation of electric-dipole spin resonance (EDSR) to achieve fast and coherent manipulation of hole spins, a pivotal aspect for quantum computing applications.

Key Experimental Findings

The authors successfully demonstrated Pauli spin blockade (PSB) in their fabricated DQD devices, a critical mechanism for spin-selective read-out in quantum computing. The study reveals coherent control over hole spins via Rabi oscillations with frequencies reaching 140 MHz, a noteworthy result indicating the potential for rapid quantum operations. Additionally, the Ramsey experiments conducted highlight dephasing times of 130 ns, underscoring the promising decoherence resilience of these hole spin qubits compared to their silicon-based counterparts.

The stability diagrams of the DQD devices, characterized by low mutual capacitance and energy level separations up to 1 meV, demonstrate robust control and manipulation of quantum states. The observed strong coupling indicated by alpha factors further validates these findings. The documentation of bias triangles and the successful lift of spin blockade through EDSR with an estimated g-factor of approximately 2 attest to the effectiveness of the magnetic field orientation and its alignment in these experiments.

Implications and Theoretical Considerations

This examination of Ge hole spin qubits establishes their viability as a scalable platform for quantum computing. The intrinsic strong spin-orbit coupling of holes presents a profound advantage for electrically controlled qubits, positing Ge as a favorable alternative to silicon in specific quantum applications. The observed anisotropy in g-factor values and their alignment-dependent behavior suggest further exploration into geometric and material properties affecting qubit performance.

Future Prospects in Quantum Computing

The reported Rabi frequencies and dephasing times invite speculation regarding the realization of fast quantum gates and long-range coupling in scalable quantum circuits. These findings open pathways for enhancing qubit control fidelity and coherence times through material and architectural optimizations, potentially foregrounding Ge-based quantum technologies. Future work may involve integrating these findings into hybrid quantum systems or leveraging anisotropy for directional logic operations.

In conclusion, this research propels the understanding and potential application of Ge hole spin qubits, offering compelling prospects for advancements in fast and scalable quantum computing technologies. The experimental achievements underscore a pivotal step toward the broader deployment of germanium in quantum information processing, setting the stage for further innovations in the field.