QuBE: a Qubit-controller with Broadband Electronics*

As the number of qubits grows in the pursuit of fault-tolerant superconducting quantum computers, existing microwave control systems pose scalability challenges. Addressing these challenges requires the integration and miniaturization of numerous microwave control units. We have developed a qubit controller that meets the stringent requirements derived from the design of the current superconducting qubits. The system has broadband capability, phase stability, and sufficient performance on timing synchronization and digital signal processing. We have demonstrated simultaneous measurements of multiple qubits with synchronized controllers and frequency multiplexing. We disclose the microwave performance, such as the stabilities of the phase and intensity obtained through the development of several controller systems for more than 60 qubits. We discuss the impact of the stabilities on gate fidelity.