Tom Ohki

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

  1. Martin Sandberg,
  2. Michael R. Vissers,
  3. Tom Ohki,
  4. Jiansong Gao,
  5. Jose Aumentado,
  6. Martin Weides,
  7. and 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.
arxiv pdf