SQ-CARS: A Scalable Quantum Control and Readout System

Qubits are the basic building blocks of a quantum processor, which require electromagnetic pulses in gigahertz (GHz) frequency range and latency in nanoseconds for control and readout. In this article, we address three main challenges associated with room-temperature electronics used for controlling and measuring superconducting qubits: scalability, direct microwave synthesis, and a unified user interface. To tackle these challenges, we have developed scalable quantum control and readout system (SQ-CARS), a system based on the ZCU111 evaluation kit. SQ-CARS is designed to be scalable, configurable, and phase-synchronized, providing multiqubit control and readout capabilities. The system offers an interactive Python framework, making it user-friendly. Scalability to a larger number of qubits is achieved by deterministic synchronization of multiple channels. The system supports direct synthesis of arbitrary vector microwave pulses using the second Nyquist zone technique, from 4 to 9 GHz. It also features onboard data processing such as tunable low-pass filters and configurable rotation blocks, enabling lock-in detection and low-latency active feedback for quantum experiments. All control and readout features are accessible through an onboard Python framework. To validate the performance of SQ-CARS, we conducted various time-domain measurements to characterize a superconducting transmon qubit. Our results were compared against traditional setups commonly used in similar experiments. With deterministic synchronization of control and readout channels and an open-source approach for programming, SQ-CARS paves the way for advanced experiments with superconducting qubits.