S. Asaad

Independent, extensible control of same-frequency superconducting qubits by selective broadcasting

  1. S. Asaad,
  2. C. Dickel,
  3. S. Poletto,
  4. A. Bruno,
  5. N. K. Langford,
  6. M. A. Rol,
  7. D. Deurloo,
  8. and L. DiCarlo
A critical ingredient for realizing large-scale quantum information processors will be the ability to make economical use of qubit control hardware. We demonstrate an extensible strategy
for reusing control hardware on same-frequency transmon qubits in a circuit QED chip with surface-code-compatible connectivity. A vector switch matrix enables selective broadcasting of input pulses to multiple transmons with individual tailoring of pulse quadratures for each, as required to minimize the effects of leakage on weakly anharmonic qubits. Using randomized benchmarking, we compare multiple broadcasting strategies that each pass the surface-code error threshold for single-qubit gates. In particular, we introduce a selective-broadcasting control strategy using five pulse primitives, which allows independent, simultaneous Clifford gates on arbitrary numbers of qubits.
arxiv pdf

Reducing intrinsic loss in superconducting resonators by surface treatment and deep etching of silicon substrates

  1. A. Bruno,
  2. G. de Lange,
  3. S. Asaad,
  4. K. L. van der Enden,
  5. N. K. Langford,
  6. and L. DiCarlo
We present microwave-frequency NbTiN resonators on silicon, systematically achieving internal quality factors above 1 M in the quantum regime. We use two techniques to reduce losses
associated with two-level systems: an additional substrate surface treatment prior to NbTiN deposition to optimize the metal-substrate interface, and deep reactive-ion etching of the substrate to displace the substrate-vacuum interfaces away from high electric fields. The temperature and power dependence of resonator behavior indicate that two-level systems still contribute significantly to energy dissipation, suggesting that more interface optimization could further improve performance.
arxiv pdf