Mark B. Ketchen

Characterization of addressability by simultaneous randomized benchmarking

  1. Jay M. Gambetta,
  2. A. D. Corcoles,
  3. S. T. Merkel,
  4. B. R. Johnson,
  5. John A. Smolin,
  6. Jerry M. Chow,
  7. Colm A. Ryan,
  8. Chad Rigetti,
  9. S. Poletto,
  10. Thomas A. Ohki,
  11. Mark B. Ketchen,
  12. and M. Steffen
The control and handling of errors arising from cross-talk and unwanted interactions in multi-qubit systems is an important issue in quantum information processing architectures. We
introduce a benchmarking protocol that provides information about the amount of addressability present in the system and implement it on coupled superconducting qubits. The protocol consists of randomized benchmarking each qubit individually and then simultaneously, and the amount of addressability is related to the difference of the average gate fidelities of those experiments. We present the results on two similar samples with different amounts of cross-talk and unwanted interactions, which agree with predictions based on simple models for the amount of residual coupling.
arxiv pdf

Superconducting qubit in waveguide cavity with coherence time approaching 0.1ms

  1. Chad Rigetti,
  2. Stefano Poletto,
  3. Jay M. Gambetta,
  4. B. L. T. Plourde,
  5. Jerry M. Chow,
  6. A. D. Corcoles,
  7. John A. Smolin,
  8. Seth T. Merkel,
  9. J. R. Rozen,
  10. George A. Keefe,
  11. Mary B. Rothwell,
  12. Mark B. Ketchen,
  13. and M. Steffen
We report a superconducting artificial atom with an observed quantum coherence time of T2*=95us and energy relaxation time T1=70us. The system consists of a single Josephson junction
transmon qubit embedded in an otherwise empty copper waveguide cavity whose lowest eigenmode is dispersively coupled to the qubit transition. We attribute the factor of four increase in the coherence quality factor relative to previous reports to device modifications aimed at reducing qubit dephasing from residual cavity photons. This simple device holds great promise as a robust and easily produced artificial quantum system whose intrinsic coherence properties are sufficient to allow tests of quantum error correction.
arxiv pdf