Optimising multi-qubit operations in a ring-resonator-based quantum processor*

A highly connected qubit network enables one to efficiently compile an arbitrary quantum operation by minimizing gate count. Recently, we showed that a highly connected superconducting qubit network could be achieved using a ring-resonator-based coupler [1].  However, in architectures with static coupling, many levels (including non-computational ones) in the extended Hilbert space may interact with each other and cause undesired shifts in the computational subspace, leading to coherent errors. Using the ring-resonator-based coupler architecture, we explore the optimization of device parameters for a given number of transmon qubits and connectivity, to achieve maximum processor performance. We also investigate the possibility of using optimal-control-techniques[2] that include the coherent errors in the system Hamiltonian to tune high-fidelity quantum operations in such connected networks consisting of five to ten qubits.

[1] Phys. Rev. Applied 16, 024018

[2] Phys Rev A.97.042348