Coherent Control of a Few-Channel Hole Type Gatemon Qubit

Area of Science:

• Quantum Information Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Gatemon qubits, electrically tunable superconducting qubits, are explored as an alternative to transmon qubits.
• Germanium/Silicon (Ge/Si) core/shell nanowires offer technologically relevant materials for quantum applications.
• Achieving high-quality Josephson junctions is crucial for qubit performance and coherence.

Purpose of the Study:

• To demonstrate full coherent control of a gatemon qubit utilizing hole carriers in a Ge/Si core/shell nanowire.
• To achieve and report the longest coherence times for group IV material gatemons.
• To investigate the quantum transport properties of the Josephson junction in the gatemon qubit.

Main Methods:

• Fabrication of a gatemon qubit using Ge/Si core/shell nanowires.
• Implementation of a straightforward and reproducible annealing technique to create a high-quality Josephson junction.
• Characterization of qubit coherence times and quantum transport through the Josephson junction.

Main Results:

• Demonstrated full coherent control of the gatemon qubit.
• Achieved the longest coherence times to date for group IV material gatemons.
• Identified that transport through the narrow Josephson junction is dominated by only two quantum channels with high transparency (up to unity).

Conclusions:

• The Ge/Si nanowire gatemon qubit platform shows significant promise for quantum information applications.
• The use of technologically relevant materials and the observed ultrastrong spin-orbit coupling in the few-channel regime offer new avenues for qubit design.
• The straightforward annealing technique for Josephson junction fabrication enhances the reproducibility and scalability of this qubit platform.