G. J. Ribeill

Measurement of a Superconducting Qubit with a Microwave Photon Counter

  1. A. Opremcak,
  2. I. V. Pechenezhskiy,
  3. C. Howington,
  4. B. G. Christensen,
  5. M. A. Beck,
  6. E. Leonard Jr.,
  7. J. Suttle,
  8. C. Wilen,
  9. K. N. Nesterov,
  10. G. J. Ribeill,
  11. T. Thorbeck,
  12. F. Schlenker,
  13. M.G. Vavilov,
  14. B. L. T. Plourde,
  15. and R. McDermott
Fast, high-fidelity measurement is a key ingredient for quantum error correction. Conventional approaches to the measurement of superconducting qubits, involving linear amplification
of a microwave probe tone followed by heterodyne detection at room temperature, do not scale well to large system sizes. Here we introduce an alternative approach to measurement based on a microwave photon counter. We demonstrate raw single-shot measurement fidelity of 92%. Moreover, we exploit the intrinsic damping of the counter to extract the energy released by the measurement process, allowing repeated high-fidelity quantum non-demolition measurements. Crucially, our scheme provides access to the classical outcome of projective quantum measurement at the millikelvin stage. In a future system, counter-based measurement could form the basis for a scalable quantum-to-classical interface.
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