Hole spin coherence in a Ge/Si heterostructure nanowire

Area of Science:

• Quantum physics
• Condensed matter physics
• Nanotechnology

Background:

• Spin qubits in semiconductor nanostructures are promising for quantum computing.
• Germanium/silicon heterostructures offer unique electronic properties for spintronics.
• Understanding spin relaxation and dephasing is crucial for qubit coherence.

Purpose of the Study:

• To measure hole spin relaxation and dephasing times in a gate-defined Ge/Si nanowire double quantum dot.
• To investigate the dominant dephasing mechanisms in this system.
• To compare dephasing properties with other semiconductor systems.

Main Methods:

• Utilized a fast pulsed-gate technique for precise control of quantum dot states.
• Employed dispersive readout for sensitive qubit state detection.
• Analyzed spin dephasing dynamics over time.

Main Results:

• Achieved an inhomogeneous dephasing time (T2*) of 0.18 μs, significantly longer than in III-V semiconductors.
• Observed exponential dephasing, characteristic of broadband noise.
• Demonstrated that Ge/Si nanowires are largely free from nuclear spin-induced dephasing.

Conclusions:

• Ge/Si nanowires exhibit superior hole spin coherence compared to traditional III-V materials.
• The observed dephasing is attributed to extrinsic broadband noise, not intrinsic nuclear spins.
• These findings highlight the potential of Ge/Si nanowires for robust quantum information processing.