Lawrence Berkeley National Laboratory’s (Berkeley Lab) Advanced Quantum Testbed (AQT) has opened up a new electronic control and measurement system for superconducting quantum processors, making engineering solutions for emerging hardware more accessible. Superconducting circuits are one of the main quantum computing technologies seeking to solve complex problems beyond the reach of classical computers.
AQT’s superconducting qubit control system, QubiC for short, is customizable and modular. QubiC performance data has been published in IEEE Transactions on Quantum Engineering. Researchers Gang Huang and Yilun Xu of Berkeley Lab’s Accelerator Technology and Applied Physics Division (ATAP) led the design of the AQT QubiC, leveraging a strong technological heritage in research and development for particle accelerators. AQT is funded by the Advanced Scientific Computing Research (ASCR) program of the United States Department of Energy Office of Science.
The Need for More Affordable Qubit Control
Quantum information processors require expensive electronic controls capable of manipulating qubits with precision. However, developing the control hardware that maximizes the performance of quantum computers is both a theoretical and an experimental challenge. Moreover, current coherence times are short-lived and most commercially available electronic equipment is designed for general use for non-quantum systems. The cost, size, and complexity of control and measurement hardware increase with an increasing number of qubits. This presents a significant hurdle for startups and junior academic research groups around the world.
AQT researchers at Berkeley Lab are tackling these control challenges by designing modular control hardware for current and future superconducting processors and open source the complete system code, so that it can be consulted, improved and operated by the wider quantum information science community.
“New electronic control systems are not suitable for quantum control systems”, explained Huang. “So quantum researchers need to scale up the control system by buying more instruments as processors get more complex. But the cost of control hardware doesn’t have to be linear or exponential, and that’s where we’re trying to ‘step in. By building this as a more accessible and affordable system from the ground up, we really know what’s going on underneath for further integrations and trying to evolve the design.’
QubiC incorporates an RF (radio frequency) FPGA (Field Programmable Gate Array) system, which
modulates signals at room temperature to manipulate and measure superconducting qubits cooled to cryogenic temperatures. AQT’s “Blizzard” cryogenic dilution refrigerator reaches very low temperatures, close to absolute zero.
QubiC’s Python-based software and firmware implement control and measurement protocols for characterizing and comparing quantum chips, optimizing one- and two-qubit gate algorithms, and mitigating errors. Experimental results demonstrated that QubiC runs quantum algorithms with promising synchronicity and speed, providing similar results to commercially available systems at lower cost.
“We are working to provide a more modular and affordable hardware control solution that offers equal or slightly better performance with the added benefits,” Huang pointed out. “But we can’t do it all on our own, so by open sourcing the code, we can find a community willing to support, contribute and grow.”
QubiC is compatible with commercial and custom designed electronic devices. As a result, testbed users from various national labs, startups, and enterprises have shown strong interest in deploying their projects using QubiC’s customizable interface.
Xu explained, “The open source of the full QubiC system stack benefits the community because more people can contribute, customize, and improve it. And as an early-career researcher involved in its design from the start, I learned to integrate different disciplines, from engineering to physics to experiments.”
Leveraging the legacy of particle accelerators
AQT’s control hardware research and development comes from a seemingly unlikely source, but one that draws on Berkeley Lab’s origins and 91-year history: particle accelerators. In their many sizes and purposes, ranging from compact medical treatment machines to expansive research facilities like the Large Hadron Collider, accelerators accelerate charged particles and channel them into a controlled beam to explore matter and energy.
As particle accelerators grow in power, the need for advanced instrumentation and control systems increases. It is essential to precisely stabilize the particle beams and the sophisticated equipment that produces them. The resulting technology and know-how can benefit many other fields, such as quantum computing.
Huang and Xu are members of the Berkeley Accelerator Controls and Instrumentation (BACI) program, where expertise in these control systems is a crucial common resource for the varied efforts of the ATAP division. BACI, supported by the General Accelerator R&D program of the DOE’s Office of High Energy Physics, has a long history of developing precision control and feedback systems for particle accelerator projects. “I’m very happy to see that previous investments for accelerator controls can now be expanded and used for qubit controls,” said Derun Li, BACI program manager.
“Particle accelerators are a critical part of Berkeley Lab’s science endeavors, so working with advanced FPGA-based RF control technology and engineering for particle beams has helped us streamline customization of quantum hardware. “, Huang added. “AQT researchers and testbed users can take advantage of the open source toolkit and gain a deeper understanding of flexible control hardware platforms that are both cost effective and scalable.”
ATAP director Cameron Geddes described the QubiC design for AQT’s superconducting processors as “classic examples of how capabilities developed for one area can benefit others in Berkeley Lab’s team science tradition.”
Open access test bench
Scalable quantum computers will require significant modifications to current tools and standard techniques, which is why AQT researchers pioneered the open-source control hardware used in the quantum computing testbed program of the Berkeley Lab which is inspired by technology transfer from particle accelerators.
By providing AQT users with full access to QubiC and its infrastructure, the wider community has access to state-of-the-art superconducting quantum processors and co-participates in their evolution, potentially making QubiC also compatible with other technologies. quantum computing.