Characterization and reduction of capacitive loss induced by sub-micron Josephson junction fabrication in superconducting qubits

By A. Dunsworth, A. Megrant, C. Quintana, Z. Chen, R. Barends, B. Burkett, B. Foxen, Yu Chen, B. Chiaro, Austin G. Fowler and 13 more. 2017

140 citations recorded by the source corpus.

Josephson junctions form the essential non-linearity for almost all superconducting qubits. The junction is formed when two superconducting electrodes come within ∼1 nm of each other. Although the capacitance of these electrodes is a small fraction of the total qubit capacitance, the nearby electric fields are more concentrated in dielectric surfaces and can contribute substantially to the total dissipation. We have developed a technique to experimentally investigate the effect of these electrodes on the quality of superconducting devices. We use λ/4 coplanar waveguide resonators to emulate lumped qubit capacitors. We add a variable number of these electrodes to the capacitive end of these resonators and measure how the additional loss scales with the number of electrodes. We then reduce this loss with fabrication techniques that limit the amount of lossy dielectrics. We then use these techniques for the fabrication of Xmon qubits on a silicon substrate to improve their energy relaxation times by a factor...

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/2a51f456928816e28dada45c736bb3d0f4cc3eb8

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In Artificial Intelligence

In Atomic and Molecular Physics, and Optics

Citations in the corpus

Realizing repeated quantum error correction in a distance-three surface code (2021, methodology): “We fabricate aluminiumbased Josephson junctions of the transmon qubits using electron-beam lithography (EBL) and shadow evaporation, and establish electrical contact between the junction metal and the niobium base-layer film using aluminum bandages [61] fabricated in a second EBL and evaporation run”
Qubit compatible superconducting interconnects (2017, methodology): “For the base substrate, we first blanket deposit 100 nm of aluminum through ebeam evaporation–the same base wiring material used in qubit fabrication [22].”