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.
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.
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. For example, even single nanosecond variations of the interaction may have an influence on the quantum state. Designing a tailored interface electronics is therefore a major challenge, both in terms of signal integrity with respect to single channels, as well as the scaling of the signal count. We developed such an interface electronics, an RFSoC-based qubit control system called QiController. In this article, we present the modular FPGA firmware design of our system. It features so-called digital unit cells, or QiCells. Each cell contains all the logic necessary to interact with a single superconducting qubit, including a custom-built RISC-V-based sequencer. Synchronization and data exchange between the cells is facilitated using a special star-point structure. Versatile routing and frequency-division multiplexing of generated signals between QiCells and converters are also supported. High-level programmability is provided using a custom Python-based description language and an associated compiler. We furthermore provide the resource utilization of our design and demonstrate its correct operation using an actual superconducting five-qubit chip.
This thesis presents the development of a superconducting qubit control and readout system based on FPGA technology, with a focus on the design of a pulse sequencer and the integration of frequency-multiplexed control. The system leverages the Quantum Instrumentation Control Kit (QICK), an open-source Xilinx RFSoC-based platform capable of direct digital synthesis and acquisition of microwave signals up to 10 GHz. The QICK firmware was extended to support the simultaneous generation and readout of multiple frequency-multiplexed tones, enabling the control and measurement of several qubits coupled to a shared feedline. This approach optimizes the number of controllable qubits relative to the available ADC and DAC resources on the RFSoC 4x2 board. Furthermore, this work includes the development of Qubase, a Python-based pulse sequencer that allows users to easily define and execute complex sequences of control and measurement pulses through the QICK Python interface. The resulting architecture is both flexible and scalable, providing a foundation for efficient multi-qubit experiments and enabling advanced techniques such as quantum error correction and real-time feedback.
Quantum circuits utilizing real time feedback techniques (such as active reset and mid-circuit measurement) are a powerful tool for NISQ-era quantum computing. Such techniques are crucial for implementing error correction protocols, and can reduce the resource requirements of certain quantum algorithms. Realizing these capabilities requires flexible, low-latency classical control. We have developed a custom FPGA-based processor architecture for QubiC, an open source platform for superconducting qubit control. Our architecture is distributed in nature, and consists of a bank of lightweight cores, each configured to control a small (1-3) number of signal generator channels. Each core is capable of executing parameterized control and readout pulses, as well as performing arbitrary control flow based on mid-circuit measurement results. We have also developed a modular compiler stack and domain-specific intermediate representation for programming the processor. Our representation allows users to specify circuits using both gate and pulse-level abstractions, and includes high-level control flow constructs (e.g. if-else blocks and loops). The compiler stack is designed to integrate with quantum software tools and programming languages, such as TrueQ, pyGSTi, and OpenQASM3. In this work, we will detail the design of both the processor and compiler stack, and demonstrate its capabilities with a quantum state teleportation experiment using transmon qubits at the LBNL Advanced Quantum Testbed.
As quantum information processors grow in quantum bit (qubit) count and functionality, the control and measurement system becomes a limiting factor to large scale extensibility. To tackle this challenge and keep pace with rapidly evolving classical control requirements, full control stack access is essential to system level optimization. We design a modular FPGA (field-programmable gate array) based system called QubiC to control and measure a superconducting quantum processing unit. The system includes room temperature electronics hardware, FPGA gateware, and engineering software. A prototype hardware module is assembled from several commercial off-the-shelf evaluation boards and in-house developed circuit boards. Gateware and software are designed to implement basic qubit control and measurement protocols. System functionality and performance are demonstrated by performing qubit chip characterization, gate optimization, and randomized benchmarking sequences on a superconducting quantum processor operating at the Advanced Quantum Testbed at Lawrence Berkeley National Laboratory. The single-qubit and two-qubit process fidelities are measured to be 0.99800.0001 and 0.9480.004 by randomized benchmarking. With fast circuit sequence loading capability, the QubiC performs randomized compiling experiments efficiently and improves the feasibility of executing more complex algorithms.
Manipulating qubits and measuring quantum processors via quantum bit control systems is traditionally done using expensive, off-the-shelf commercial electronics setups. Previously, we have introduced QubiC, an open-source FPGA-based quantum bit control system developed at Lawrence Berkeley National Laboratory. After a few years of operating on the QubiC 1.0, we realized the urgent requirements on the mid-circuits measurement and feed forward to implement advanced quantum algorithms. This requirement led to engineering a novel QubiC 2.0 on top of the RFSoC technique, incorporating enriched features. The QubiC 2.0. presented in this manuscript is implemented on the Xilinx evaluation board ZCU216. We developed a portable FPGA gateware with a lean soft processor to handle the quantum commands on the fly. Further, we created a distributed architecture with multiple processors, with a one-to-one mapping between processors and qubits, creating a parallel qubit control and measurement. Like a regular CPU, these processors access pulse envelope commands with parameterized amplitude, phase, and frequency to generate pulse information on the FPGA to ensure the speed and reusability of the entire quantum circuit. The Python software layer abstracts the low-level gateware and provides the compiler, assembler, and remote procedure call for host-to-board communication. The compiled software runs on a Python runtime environment, interfacing with the low-level gateware and hardware connected to a Quantum Processing Unit, creating a full-stack quantum bit control system. We demonstrate the architecture and the broad capabilities of QubiC 2.0 with a simplified feed forward experiment on a conditional circuit.
We introduce a Xilinx RF System-on-Chip (RFSoC)-based qubit controller (called the Quantum Instrumentation Control Kit, or QICK for short), which supports the direct synthesis of control pulses with carrier frequencies of up to 6 GHz. The QICK can control multiple qubits or other quantum devices. The QICK consists of a digital board hosting an RFSoC field-programmable gate array, custom firmware, and software and an optional companion custom-designed analog front-end board. We characterize the analog performance of the system as well as its digital latency, important for quantum error correction and feedback protocols. We benchmark the controller by performing standard characterizations of a transmon qubit. We achieve an average gate fidelity of Favg=99.93%. All of the schematics, firmware, and software are open-source.