J. Chang, M. R. Vissers, A. D. Corcoles, M. Sandberg, J. Gao, David W. Abraham, Jerry M. Chow, Jay M. Gambetta, M. B. Rothwell, G. A. Keefe, Matthias Steffen, D. P. Pappas
We demonstrate enhanced relaxation and dephasing times of transmon qubits, up to ~ 60 \mu s by fabricating the interdigitated shunting capacitors using titanium nitride (TiN). Compared to lift-off aluminum deposited simultaneously with the Josephson junction, this represents as much as a six-fold improvement and provides evidence that previous planar transmon coherence times are limited by surface losses from two-level system (TLS) defects residing at or near interfaces. Concurrently, we observe an anomalous temperature dependent frequency shift of TiN resonators which is inconsistent with the predicted TLS model.
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http://arxiv.org/abs/1303.4071
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