Sub-micrometer epitaxial Josephson junctions for quantum circuits

Abstract

We present a fabrication scheme and testing results for epitaxial sub-micrometer Josephson junctions. The junctions are made using a high-temperature (1170 K) "via process" yielding junctions as small as 0.8 mu m in diameter by use of optical lithography. Sapphire (Al2O3) tunnel-barriers are grown on an epitaxial Re/Ti multilayer base-electrode. We have fabricated devices with both Re and Al top electrodes. While room-temperature (295 K) resistance versus area data are favorable for both types of top electrodes, the low-temperature (50 mK) data show that junctions with the Al top electrode have a much higher subgap resistance. The microwave loss properties of the junctions have been measured by use of superconducting Josephson junction qubits. The results show that high subgap resistance correlates to improved qubit performance.

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Cited by in corpus (7)

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• Bottom-up superconducting and Josephson junction devices inside a group-IV semiconductor
• Superconducting-semiconductor quantum devices: from qubits to particle detectors
• The influence of pinholes and weak-points in aluminium-oxide Josephson junctions
• Material matters in superconducting qubits