A quantum dot in germanium proximitized by a superconductor.

Area of Science:

• Quantum physics
• Materials science
• Condensed matter physics

Background:

• Germanium is a promising group IV material for superconductor-semiconductor hybrid devices.
• Topological superconductivity is crucial for robust quantum information processing.
• Quantum dots offer a platform for exploring novel quantum phenomena.

Purpose of the Study:

• To demonstrate a tunable quantum dot in a germanium heterostructure proximitized by a superconducting lead.
• To investigate the interplay between quantum dots and superconductivity in germanium.
• To explore the potential of germanium for topological quantum computing and qubit modalities.

Main Methods:

• Fabrication of a Ge/SiGe heterostructure with a platinum germanosilicide (PtSiGe) superconducting lead.
• Creation of a superconducting lead-quantum dot-superconducting lead junction.
• Characterization of coupling strength, charging energy, induced gap, and critical magnetic fields.

Main Results:

• Demonstrated tunability of coupling strength and gate control over energy ratios.
• Achieved control over the system's ground state parity (even/odd).
• Measured a critical out-of-plane magnetic field of 0.90 ± 0.04 T and observed sub-gap spin splitting.

Conclusions:

• The demonstrated germanium-based quantum dot platform is suitable for exploring topological superconductivity.
• This work opens avenues for germanium-based superconducting qubits and Josephson junction arrays.
• The findings contribute to the development of advanced quantum devices utilizing group IV materials.