U. Patel

Phonon-Mediated Quasiparticle Poisoning of Superconducting Microwave Resonators

  1. U. Patel,
  2. Ivan V. Pechenezhskiy,
  3. B. L. T. Plourde,
  4. M.G. Vavilov,
  5. and R. McDermott
Nonequilibrium quasiparticles represent a significant source of decoherence in superconducting quantum circuits. Here we investigate the mechanism of quasiparticle poisoning in devices
subjected to local quasiparticle injection. We find that quasiparticle poisoning is dominated by the propagation of pair-breaking phonons across the chip. We characterize the energy dependence of the timescale for quasiparticle poisoning. Finally, we observe that incorporation of extensive normal metal quasiparticle traps leads to a more than order of magnitude reduction in quasiparticle loss for a given injected quasiparticle power.
arxiv pdf

Coherent Josephson phase qubit with a single crystal silicon capacitor

  1. U. Patel,
  2. Y. Gao,
  3. D. Hover,
  4. G. J. Ribeill,
  5. S. Sendelbach,
  6. and R. McDermott
We have incorporated a single crystal silicon shunt capacitor into a Josephson phase qubit. The capacitor is derived from a commercial silicon-on-insulator wafer. Bosch reactive ion
etching is used to create a suspended silicon membrane; subsequent metallization on both sides is used to form the capacitor. The superior dielectric loss of the crystalline silicon leads to a significant increase in qubit energy relaxation times. T1 times up to 1.6 micro-second were measured, more than a factor of two greater than those seen in amorphous phase qubits. The design is readily scalable to larger integrated circuits incorporating multiple qubits and resonators.
arxiv pdf