Open source control hardware for quantum computers

Schematic of the QubiC prototype showing the electronic hardware at room temperature. Credit: Gang Huang and Yilun/Berkeley Lab

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 was 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, it is both a theoretical and an experimental challenge to develop control hardware that maximizes the performance of quantum computers. 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,” Huang explained. “Quantum researchers therefore need to expand the control system by purchasing more instruments as processors become more complex. But the cost of control hardware doesn’t have to be linear or exponential, and that’s where we try to come 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 scale 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.

Researchers Gang Huang and Yilun Xu led the design of QubiC based on robust research and development for particle accelerators at the Berkeley Laboratory. Credit: Christian Jünger/Berkeley Lab

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 results similar 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 emphasized. “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, “Open sourcing the full QubiC system stack benefits the community as 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.

Open source control hardware for quantum computers

The researchers designed and opened up a modular electronic control system based on a field-programmable gate array (FPGA) called QubiC for superconducting quantum information processors. Credit: Berkeley Laboratory

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 DOE’s Office of High Energy Physics General Accelerator R&D Program, has a long history of developing precision control and feedback systems for particle accelerator projects. “I am very happy to see that previous investments for accelerator controls can now be expanded and used for qubit controls,” said BACI program manager Derun Li.

“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. added Huang. “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 the team science tradition. of Berkeley Lab”.

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.


How a new radio frequency control system improves quantum computers


More information:

Yilun Xu et al, QubiC: An Open Source FPGA-Based Control and Measurement System for Superconducting Quantum Information Processors, IEEE Transactions on Quantum Engineering (2021). DOI: 10.1109/TQE.2021.3116540

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Lawrence Berkeley National Laboratory

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