Direct all-to-all controlled-Z operation mediated via a central element on a star topology quantum processor - part 1

Increasing connectivity and decreasing qubit delocalization without compromising the speed or accuracy of elementary gate operations are key challenges in developing large-scale superconducting quantum computers. In this context, we present our theoretical study of a unit cell of a hexagonal qubit lattice [1], where each qubit pair is coupled through two tunable couplers and a central shared element. This enables tunable, on-demand, all-to-all connectivity between each qubit pair within the unit cell.

In this talk, we provide a thorough theoretical analysis of a direct CZ gate between two peripheral qubits on the hexagonal qubit lattice. We also discuss both analytical and numerical studies on a complete error model, including delocalization-induced crosstalk, spectator effects and decoherence errors. Experimental demonstration of the direct CZ gate is presented in part 2 of the talk.

We conclude that our multi-mode coupling architecture strikes a good balance between increased connectivity and available parallelism, particularly when several interacting unit cells form a quantum processing unit. We anticipate that these results will pave the way for high-connectivity quantum processors with efficient, low-overhead novel quantum algorithms.