Andreev Modes from Phase Winding in a Full-Shell Nanowire-Based Transmon

Area of Science:

• Quantum computing
• Condensed matter physics
• Superconductivity

Background:

• Transmon qubits are a leading platform for quantum computation.
• Superconducting shells on nanowires offer novel qubit designs.
• Reentrant superconductivity and the Little-Parks effect present unique physical phenomena.

Purpose of the Study:

• To investigate the behavior of transmon qubits utilizing semiconductor nanowires with superconducting shells.
• To explore the impact of reentrant superconductivity and phase winding on qubit coherence.
• To understand the role of Andreev states in qubit performance.

Main Methods:

• Fabrication of transmon qubits from semiconductor nanowires with integrated superconducting shells.
• Experimental observation of coherent transitions under varying gate voltages.
• Numerical simulations to analyze the influence of winding-induced Andreev states.

Main Results:

• Numerous coherent qubit transitions were observed in the first reentrant lobe (2π phase winding) but not the zeroth lobe.
• Increasing junction density via gate voltage led to suppression and eventual loss of qubit coherence in the first lobe.
• Experimental findings align with numerical simulations highlighting Andreev states.

Conclusions:

• The study demonstrates the critical role of winding-induced Andreev states in the performance of nanowire-based transmon qubits.
• Coherence in these qubits is sensitive to phase winding and junction density.
• These findings provide insights for designing and improving superconducting quantum devices.