Three researchers take measurements from a circuit board at a test bench

BACI researchers led the QubiC design, leveraging expertise and robust technologies based on particle-accelerator controls and instrumentation.

As quantum information processors continue to advance in both quantum bit (qubit) count and functionality, the control and measurement systems for the qubits pose challenges to large-scale extensibility. Unrestricted access to the entire control stack becomes imperative for comprehensive system-level optimization.

BACI researchers have developed an open-source quantum bit control system named QubiC, designed to control and measure a superconducting quantum processing unit.

QubiC is based on field-programmable gate arrays (FPGAs), a commercial off-the-shelf technology familiar to classical control systems. The development of the QubiC 1.0 system commenced in 2018 and encompasses room-temperature hardware, FPGA gateware, and standard engineering software. Using the established Xilinx VC707 FPGAs, QubiC 1.0 excels in qubit chip characterization, gate optimization, and executing randomized benchmarking sequences on a superconducting quantum processor.

Two researchers work with electronics at a test bench.

The QubiC system continues to evolve to serve the needs of quantum processing.

Following years of qubit calibration and testing with QubiC 1.0, we identified the necessity for mid-circuit measurements and feed-forward capabilities to implement advanced quantum algorithms effectively. Subsequently, leveraging the advancements in radiofrequency system-on-a-chip (RFSoC) technology, the QubiC system underwent an upgrade to QubiC 2.0, now hosted on a Xilinx ZCU216 evaluation board.

The system incorporates portable FPGA gateware with a simplified processor, facilitating on-the-fly command handling. Embracing a multi-core distributed architecture for design simplicity and scalability, each qubit is assigned a dedicated processor core. The system employs pre-stored pulse envelopes in the FPGA’s block RAM, ensuring speed and reusability throughout the quantum circuit. Parameters such as amplitude, phase, and frequency can be dynamically updated from pulse to pulse.

The quantum circuit is programmable in a high-level language supporting pulse- and native-gate-level programming, including high-level control flow constructs. The hardware is all at room temperature, even if the controlled qubits are in a cryogenic environment.