Coherence in a transmon qubit with epitaxial tunnel junctions

TL;DR

This paper reports the development of scalable transmon qubits with epitaxial tunnel junctions, achieving high coherence times and detailed loss analysis, advancing quantum computing hardware.

Contribution

Introduces a new transmon qubit design using epitaxial tunnel junctions and optical lithography for improved scalability and coherence.

Findings

Relaxation time T1 is approximately 0.72-0.86 microseconds.

Dephasing time T2 is slightly larger than T1, reaching 1.36 microseconds.

Qubit loss closely matches the sum of individual component losses.

Abstract

We developed transmon qubits based on epitaxial tunnel junctions and interdigitated capacitors. This multileveled qubit, patterned by use of all-optical lithography, is a step towards scalable qubits with a high integration density. The relaxation time T1 is .72-.86mu sec and the ensemble dephasing time T2 is slightly larger than T1. The dephasing time T2 (1.36mu sec) is nearly energy-relaxation-limited. Qubit spectroscopy yields weaker level splitting than observed in qubits with amorphous barriers in equivalent-size junctions. The qubit's inferred microwave loss closely matches the weighted losses of the individual elements (junction, wiring dielectric, and interdigitated capacitor), determined by independent resonator measurements.