Quantum circuit elements using nitride superconductors
Future advances in qubit performance are likely to be unlocked through materialimprovements for linear and nonlinear superconducting circuit elements. Through a structure-property-performance framework, nitride superconducting thin filmswill be explored for use as resonator and Josephson junction components. Specifically, Plasma Assisted Molecular Beam Epitaxy (PAMBE) is used to synthesize nitride binary and ternary compounds such as TiN, NbN, ZrN, NbTiN,& ZrTiN on sapphire wafers. Alloyed thin films that have an engineered lattice constant are designed and synthesized to match the in-plane atomic spacing of nitride dielectric materials such as AlN & ScN. The films are grown at temperatures below 1000 oC, exhibit a superconducting critical temperature over 15 K, a root-mean-square surface roughness less than 1 Å, internal quality factors at low powers above 2M, non-saturating loss-behavior at high powers, and low kinetic inductance. Insight fromprototype trilayer materials and epitaxial Josephson junctions identify additional material challenges and potential for qubit devices that operate at higher temperatures.
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