Calibration of the cross-resonance two-qubit gate between directly-coupled transmons

  1. A. D. Patterson,
  2. J. Rahamim,
  3. T. Tsunoda,
  4. P. Spring,
  5. S. Jebari,
  6. K. Ratter,
  7. M. Mergenthaler,
  8. G. Tancredi,
  9. B. Vlastakis,
  10. M. Esposito,
  11. and P. J. Leek
Quantum computation requires the precise control of the evolution of a quantum system, typically through application of discrete quantum logic gates on a set of qubits. Here, we use the cross-resonance interaction to implement a gate between two superconducting transmon qubits with a direct static dispersive coupling. We demonstrate a practical calibration procedure for the optimization of the gate, combining continuous and repeated-gate Hamiltonian tomography with step-wise reduction of dominant two-qubit coherent errors through mapping to microwave control parameters. We show experimentally that this procedure can enable a ZX^−π/2 gate with a fidelity F=97.0(7)%, measured with interleaved randomized benchmarking. We show this in a architecture with out-of-plane control and readout that is readily extensible to larger scale quantum circuits.
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