Y. Gao

Dispersive Qubit Readout with Intrinsic Resonator Reset

  1. M. Jerger,
  2. F. Motzoi,
  3. Y. Gao,
  4. C. Dickel,
  5. L. Buchmann,
  6. A. Bengtsson,
  7. G. Tancredi,
  8. Ch. Warren,
  9. J. Bylander,
  10. D. DiVincenzo,
  11. R. Barends,
  12. and P. A. Bushev
A key challenge in quantum computing is speeding up measurement and initialization. Here, we experimentally demonstrate a dispersive measurement method for superconducting qubits that
simultaneously measures the qubit and returns the readout resonator to its initial state. The approach is based on universal analytical pulses and requires knowledge of the qubit and resonator parameters, but needs no direct optimization of the pulse shape, even when accounting for the nonlinearity of the system. Moreover, the method generalizes to measuring an arbitrary number of modes and states. For the qubit readout, we can drive the resonator to ∼102 photons and back to ∼10−3 photons in less than 3κ−1, while still achieving a T1-limited assignment error below 1\%. We also present universal pulse shapes and experimental results for qutrit readout.
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