1211.2017 (Martin Sandberg et al.)

Long-lived, radiation-suppressed superconducting quantum bit in a planar
geometry    [PDF]

Martin Sandberg, Michael R. Vissers, Tom Ohki, Jiansong Gao, Jose Aumentado, Martin Weides, David P. Pappas

We present a superconducting qubit design that is fabricated in a 2D geometry over a superconducting ground plane to enhance the lifetime. The qubit is coupled to a microstrip resonator for readout. The circuit is fabricated on a silicon substrate using low loss, stoichiometric titanium nitride for capacitor pads and small, shadow-evaporated aluminum/aluminum-oxide junctions. We observe qubit relaxation and coherence times ($T_1$ and $T_2$) of 11.7 $\pm$ 0.2 $\mu$s and 8.7 $\pm$ 0.3 $\mu$s, respectively. Calculations show that the proximity of the superconducting plane suppresses the otherwise high radiation loss of the qubit. A significant increase in $T_1$ is projected for a reduced qubit-to-superconducting plane separation.

View original: http://arxiv.org/abs/1211.2017