Pseudo-2D superconducting quantum computing circuit for the surface code

  1. H. Mukai,
  2. K. Sakata,
  3. S.J. Devitt,
  4. R. Wang,
  5. Y. Zhou,
  6. Y. Nakajima,
  7. and J. S. Tsai
Of the many potential hardware platforms, superconducting quantum circuits have become the leading contender for constructing a scalable quantum computing system. All current architecture
designs necessitate a 2D arrangement of superconducting qubits with nearest neighbour interactions, compatible with powerful quantum error correction using the surface code. A major hurdle for scalability in superconducting systems is the so called wiring problem, where qubits internal to a chip-set become inaccessible for external control/readout lines. Current approaches resort to intricate and exotic 3D wiring and packaging technology which is a significant engineering challenge to realize, while maintaining qubit fidelity. Here we solve this problem and present a modified superconducting scalable micro-architecture that does not require any 3D external line technology and reverts back to a completely planar design. This is enabled by a new pseudo-2D resonator network that provides inter-qubit connections via airbridges. We carried out experiments to examine the feasibility of the newly introduced airbridge component. The measured quality factor of these new inter-qubit resonators is sufficient for high fidelity gates, below the threshold for the surface code, with negligible measured cross-talk. The resulting physical separation of the external wirings and the inter-qubit connections on-chip should reduce cross-talk and decoherence as the chip-set increases in size. This result demonstrates that a large-scale, fully error corrected quantum computer can be constructed by monolithic integration technologies without additional overhead and without special packaging know-hows.

Vacuum induced Aulter-Townes splitting in a superconducting artificial atom

  1. Z.H. Peng,
  2. J.H. Ding,
  3. Y. Zhou,
  4. L.L. Ying,
  5. Z. Wang,
  6. L. Zhou,
  7. L.M. Kuang,
  8. Yu-xi Liu,
  9. O. Astfiev,
  10. and J. S. Tsai
We study experimentally a vacuum induced Aulter-Townes doublet in a superconducting three-level artificial atom strongly coupled to a coplanar waveguide resonator and simultaneously
to a transmission line. The Aulter-Townes splitting is observed in the reflection spectrum of the three-level atom when the transition between two excited states is resonant with the resonator. By varying an amplitude of the driving field applied to the resonator, we observe quantum-to-classical transition of the Aulter-Townes splitting. Our results may pave the way for the control of microwaves by single photons.