A modular RFSoC-based approach to interface superconducting quantum bits

Quantum computers will be a revolutionary extension of the heterogeneous computing world. They consist of many quantum bits (qubits) and require a careful design of the interface between the classical computer architecture and the quantum processor. Even single nanosecond variations of the interaction may have an influence on the quantum state. In this paper, we present the modular design of the FPGA firmware which is part of our qubit control electronics. It features so-called digital unit cells where each cell contains all the logic necessary to interact with a single superconducting qubit. The cell includes a custom-built RISC-V-based sequencer, as well as two signal generators and a signal recorder. Internal communication within the cell is handled using a modified Wishbone bus with custom 2-to-N interconnect and deterministic broadcast functionality. We furthermore provide the resource utilization of our design and demonstrate its correct operation using an actual superconducting five qubit chip.