Coherence in a transmon qubit with epitaxial tunnel junctions
ORAL
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 $T_1$ is $.72-.86\;\rm{\mu sec}$ and the ensemble dephasing time $T_2^*$ is slightly larger than $T_1$. The dephasing time $T_2$ ($1.36\;\rm{\mu sec}$) 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.
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