A modular superconducting qubit architecture using multi-chip tunable couplers*

Modular architectures have been used to scale up the number of superconducting qubits, where high-yielding chips with small numbers of qubits are combined to form a larger superconducting quantum processor. In parallel, tunable couplers were introduced as a way to turn off qubit-qubit interactions, allowing for lower error rates and more flexibility in frequency allocation. In order to combine the scalability of modular architectures and the performance enhancements and flexibility of tunable couplers, we have implemented an extension of the floating coupler and introduced the multi-chip tunable coupler to mediate qubit-qubit interactions between separate chips of a modular device. 

In this talk, I will present the multi-chip tunable coupler in the context of Rigetti’s past work on implementing scalable architectures and flexible gate schemes. Specifically, we test design variations with increasing packaging complexity. In all of the variations, we find that the multi-chip tunable coupler can mediate both high- and low-coupling interactions between separated qubits using parametric-resonance gates. Finally, we show that two-qubit gates activated between qubits on separate chips perform comparably to two-qubit gates on a single-chip device.