Large-scale qubit systems represent the future of superconducting quantum computing. As the number of qubits and functions increases, the current qubit control architectures struggle to achieve large-scale expansion. To address this issue, we have developed a field-programmable gate array-based scheduling system, which serves as a control architecture deployed on measurement and control hardware. This system achieves the generation of multi-channel long sequence pulses using minimal storage space, with reusable envelope and instruction designs. The envelopes and instructions are preloaded into the electronics, with each instruction corresponding to a different segment of the output waveform. The architecture we designed allows for extended pulse control lengths and more complex experiments without the requirement for external storage resources. We present the resource utilization of the implementation and compare it with previous measurements under different qubit counts. To verify the functionality of the system, we conducted a series of performance tests and characterization experiments on the deployed electronics. The measured single-qubit relaxation time T1 is 34.1 μs, and the dephasing time T2* is 25.8 μs. We characterized the quality of the control pulses using a randomized benchmarking protocol, achieving an average fidelity of 99.962%.
Large-scale qubit systems represent the future of superconducting quantum computing. As the number of qubits and functions increases, the current qubit control architectures struggle to achieve large-scale expansion. To address this issue, we have developed a field-programmable gate array-based scheduling system, which serves as a control architecture deployed on measurement and control hardware. This system achieves the generation of multi-channel long sequence pulses using minimal storage space, with reusable envelope and instruction designs. The envelopes and instructions are preloaded into the electronics, with each instruction corresponding to a different segment of the output waveform. The architecture we designed allows for extended pulse control lengths and more complex experiments without the requirement for external storage resources. We present the resource utilization of the implementation and compare it with previous measurements under different qubit counts. To verify the functionality of the system, we conducted a series of performance tests and characterization experiments on the deployed electronics. The measured single-qubit relaxation time T1 is 34.1 μs, and the dephasing time T2* is 25.8 μs. We characterized the quality of the control pulses using a randomized benchmarking protocol, achieving an average fidelity of 99.962%.
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.
Electronic systems for qubit control and measurement serve as a bridge between quantum programming language and quantum information processors. With the rapid development of superconducting quantum circuit technology, synchronization in a large-scale system, low-latency execution, and low noise are required for electronic systems. Here, we present a field-programmable gate array (FPGA)-based electronic system with a distributed synchronous clock and trigger architecture. The system supports synchronous control of qubits with jitters of ∼5 ps. We implement a real-time digital signal processing system in the FPGA, enabling precise timing control, arbitrary waveform generation, in-phase and quadrature demodulation for qubit state discrimination, and the generation of real-time qubit-state-dependent trigger signals for feedback/feedforward control. The hardware and firmware low-latency design reduces the feedback/feedforward latency of the electronic system to 125 ns, significantly less than the decoherence times of the qubit. Finally, we demonstrate the functionalities and low-noise performance of this system using a fluxonium quantum processor.
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 present the development of an open-source FPGA (field-programmable gate array) based processor for pulse-level qubit control. Our processor is designed primarily as an upgrade to QubiC, an open source qubit control platform, but can also be adapted to other systems. The processor is distributed in nature, with one core per arbitrary waveform generator (AWG); simplifying the design and allowing for straightforward scaling. Each processor core implements an instruction set consisting of timed pulse commands as well as simple arithmetic and branching instructions. Our design also includes interfaces for synchronizing the different cores and requesting/receiving (optionally processed) measurement results. Together, these features will allow a user to program arbitrary control flow within a quantum circuit based on previous measurement results. In this poster, we detail our design along with the expected resource utilization on the Xilinx Virtex 7 FPGA, and present pulse-level simulations of our system in the context of a simple feedback experiment.
Researchers manipulate and measure quantum processing units via the classical electronics control system. We developed an open-source FPGA-based quantum bit control system called QubiC for superconducting qubits. After years of qubit calibration and testing experience on QubiC 1.0, we recognized the need for mid-circuit measurement and feed-forward capabilities to implement advanced quantum algorithms, and upgraded the system to QubiC 2.0 on an AMD ZCU216 RFSoC evaluation board with all these enriched features. The system uses portable FPGA gateware with a simplified processor to handle commands on-the-fly. For design simplicity and straightforward scaling, we adopted a multi-core distributed architecture, assigning one processor core per qubit. The pulses combine the unique pulse envelope and carrier information specified in a command. Each pulse envelope is pre-stored in the FPGA's block RAMs, ensuring speed and reusability throughout the quantum circuit, while pulse parameters including amplitude, phase, and frequency can be updated from pulse to pulse. The software stack is developed in Python, running on both the FPGA's ARM core and a host computer via XML-RPC. Quantum circuits can be described in a high-level language supporting both pulse-level and native-gate-level programming with high-level control flow constructs, and are compiled into binary commands loaded into the FPGA. With QubiC 2.0, we achieved multi-FPGA synchronization and low-latency data communication, and demonstrated feed-forward experiments on conditional circuits. The system also serves as a platform for artificial intelligence and machine learning driven quantum control, such as FPGA-based real-time quantum state discrimination. The enhanced QubiC system provides researchers with powerful tools to explore and implement advanced quantum algorithms and applications.
We have developed an electronic hardware system for the control and readout of multi-superconducting qubit devices. The hardware system is based on the design ideas of good scalability, high synchronization and low latency. The system, housed inside a VPX-6U chassis, includes multiple arbitrary-waveform generator (AWG) channels, analog-digital-converter (ADC) channels as well as direct current source channels. The system can be used for the control and readout of up to twelve superconducting transmon qubits in one chassis, and control and readout of more and more qubit can be carried out by interconnecting the chassis. By using field programmable gate array (FPGA) processors, the system incorporates three features that are specifically useful for superconducting qubit research. Firstly, qubit signals can be processed using the on-board FPGA after being acquired by ADCs, significantly reducing data processing time and data amount for storage and transmission. Secondly, different output modes, such as direct output and sequential output modes, of AWG can be implemented with pre-encoded FPGA. Thirdly, with data acquisition ADCs and controlAWGs jointly controlled by the same FPGA, the feedback latency can be reduced, and in ourtest a 178.4 ns latency time is realized. This is very useful for future quantum feedback experiments. Finally, we demonstrate the functionality of the system by applying the system to the control and readout of a 10 qubit superconducting quantum processor.
Modern experiments with fundamental quantum systems - like ultracold atoms, trapped ions, and single photons - are managed by a control system formed by a number of input/output electronic channels governed by a computer. In hybrid quantum systems, where two or more quantum systems are combined and made to interact, establishing an efficient control system is particularly challenging due to the higher complexity, especially when each single quantum system is characterized by a different time scale. Here we present a new control apparatus specifically designed to efficiently manage hybrid quantum systems. The apparatus is formed by a network of fast communicating Field Programmable Gate Arrays (FPGAs), the action of which is administrated by a software. Both hardware and software share the same tree-like structure, which ensures a full scalability of the control apparatus. In the hardware, a master board acts on a number of slave boards, each of which is equipped with an FPGA that locally drives analog and digital input/output channels and radiofrequency outputs up to 400 MHz. The software is designed to be a general platform for managing both commercial and home-made instruments in a user-friendly and intuitive graphical user interface. The architecture ensures that complex control protocols can be carried out, such as performing of concurrent commands loops by acting on different channels, the generation of multi-variable error functions, and the implementation of self-optimization procedures. Although designed for managing experiments with hybrid quantum systems, in particular with atom-ion mixtures, this control apparatus can in principle be used in any experiment in atomic, molecular, and optical physics.