J. D. Strand

First-order sideband transitions with flux-driven asymmetric transmon qubits

  1. J. D. Strand,
  2. Matthew Ware,
  3. Félix Beaudoin,
  4. T. A. Ohki,
  5. B. R. Johnson,
  6. Alexandre Blais,
  7. and B. L. T. Plourde
We demonstrate rapid, first-order sideband transitions between a superconducting resonator and a frequency-modulated transmon qubit. The qubit contains a substantial asymmetry between
its Josephson junctions leading to a linear portion of the energy band near the resonator frequency. The sideband transitions are driven with a magnetic flux signal of a few hundred MHz coupled to the qubit. This modulates the qubit splitting at a frequency near the detuning between the dressed qubit and resonator frequencies, leading to rates up to 85 MHz for exchanging quanta between the qubit and resonator.
arxiv pdf

Process verification of two-qubit quantum gates by randomized benchmarking

  1. A. D. Córcoles,
  2. Jay M. Gambetta,
  3. Jerry M. Chow,
  4. John A. Smolin,
  5. Matthew Ware,
  6. J. D. Strand,
  7. B. L. T. Plourde,
  8. and M. Steffen
We implement a complete randomized benchmarking protocol on a system of two superconducting qubits. The protocol consists of randomizing over gates in the Clifford group, which experimentally
are generated via an improved two-qubit cross-resonance gate implementation and single-qubit unitaries. From this we extract an optimal average error per Clifford of 0.0936. We also perform an interleaved experiment, alternating our optimal two-qubit gate with random two-qubit Clifford gates, to obtain a two-qubit gate error of 0.0653. We compare these values with a two-qubit gate error of ~0.12 obtained from quantum process tomography, which is likely limited by state preparation and measurement errors.
arxiv pdf