D. Rugar, H.J. Mamin, et al.
Applied Physics Letters
We demonstrate a superconducting transmon qubit in which a Josephson junction has been engineered to act as its own parallel shunt capacitor. This merged-element transmon potentially offers a smaller footprint than conventional transmons. Because it concentrates the electromagnetic energy inside the junction, it reduces the relative electric field participation from other interfaces. By combining micrometer-scale Al/AlOx/Al junctions with long oxidations, we produce functional devices with EJ/EC in the low-transmon regime (EJ/EC≲30). Cryogenic I-V measurements show a sharp dI/dV structure with low subgap conduction. Qubit spectroscopy of tunable versions shows a small number of avoided level crossings, suggesting the presence of two-level systems. We observe mean T1 times typically in the range of 10-90μs, with some annealed devices exhibiting T1>100μs over several hours. The results suggest that energy relaxation in conventional small-junction transmons is not limited by junction loss.
D. Rugar, H.J. Mamin, et al.
Applied Physics Letters
T.H. Oosterkamp, Martino Poggio, et al.
Applied Physics Letters
H. Huang, Krystelle Lionti, et al.
IITC/AMC 2016
F. Chen, E. Huang, et al.
IITC 2010