One of the most highly-attended workshops at IEEE Quantum Week — the IEEE International Conference on Quantum Computing and Engineering (QCE) in September 2022 at Boulder, Colorado was organized by researchers from the Advanced Quantum Testbed (AQT) at Lawrence Berkeley National Lab (Berkeley Lab). Motivated by deep scientific inquiry and technological needs, the one-day hybrid workshop titled “Classical Control Systems for Quantum Computing,” led by Kasra Nowrouzi, Anastasiia Butko, and Gang Huang, brought together an additional 12 quantum researchers and industry leaders from top research and development programs worldwide. The workshop was a unique opportunity for the growing number of stakeholders in a fast-evolving field to share the latest experimental control advances across different technologies.
AQT at Berkeley Lab is a state-of-the-art collaborative research laboratory to advance quantum computing funded by the U.S. Department of Energy Office of Science Advanced Scientific Computing Research program (ASCR) since 2018. The third annual open user call for user proposals is currently underway.
The Controls Landscape: Challenges and Advances
Quantum researchers push the limits of Noisy Intermediate-Scale Quantum (NISQ) hardware in several ways. They’re engineering novel qubits resilient to noise and decoherence, developing software- and hardware-based mitigation tools against noise, and fabricating novel quantum processors with increasing size and complexity. In addition, experts in quantum and hybrid quantum-classical algorithms continue to place increasingly complex demands on control systems. As a result, classical control electronic systems that can harness and optimize the performance of quantum computers require more advanced features for control and readout. However, manipulating an increasing number of qubits with precision while mitigating noise and crosstalk errors often depends on the type of architecture, making system-wide affordability, flexibility, and efficiency challenging to balance for research groups.
AQT’s head of hardware, Kasra Nowrouzi, acknowledged the inherent advantages and challenges of such a varied control landscape given the field’s current stage in development.
“There are different paths to developing classical controls for quantum information systems, including commercially available solutions, proprietary integrated controls, and open source systems. While these solutions have enabled experimental breakthroughs worldwide, including at AQT, there are no perfect comprehensive control solutions to meet all experimental needs. After many years of parallel or divergent developments, we felt it was time for the community to come together and jointly plan the path forward” said Nowrouzi.
During the workshop, several speakers from industry, academia, and national labs discussed why it’s vital to better understand the real-time control requirements as system needs and size increase for new quantum circuits. For example, the gap is still wide between the existing electronic controls, including cryocontrols for superconducting quantum hardware, and those needed for future fault-tolerant, universal error-corrected quantum processors.
“Quantum control requires the careful orchestration of classical computing and electronics, across multiple temperature domains. IEEE Quantum Week is an ideal venue for workshops and tutorials on this cross-cutting area that spans several disciplines in engineering and physics. We are pleased to bring together industry, academia, and government labs to foster collaboration and new directions in research and development in this critical part of the quantum infrastructure,” said Greg Byrd, North Carolina State University professor and IEEE Quantum Week 2022 general chair.
The live and virtual audiences during Q&As raised several questions about how to best manage the overlap of efforts. For example, some attendees asked about the interplay between the new generation of proprietary and commercial controls being developed in industry to support the increasing complexity of quantum processors and whether those can be afforded by smaller, agile research groups in academia and national labs. At the same time, others asked about the value in broad conceptual explorations rooted in flexible, modular, and open-sourced hardware and software platforms across the publicly-funded ecosystem, which are currently available to a broad set of users and how to scale them for potential commercial use or more demanding experiments.
Collaboration between public research programs and industry to make the controls solution flexible was common throughout the workshop. Many speakers also pointed out that open source efforts are one of the most helpful approaches to test control solutions while training future researchers in quantum information science and technology.
“We are delighted that the workshop at IEEE Quantum Week 2022 organized by Berkeley Lab had an impressive lineup and was one of the most well-attended. It was a great success in bringing together developers and scientific users of controls from many companies and research labs to discuss the scientific needs, technological challenges, and opportunities going forward. We hope to see this line of conversation expand in the coming years,” said Hausi Müller, co-chair IEEE Future Directions Quantum Initiative and IEEE Quantum Week steering committee chair.
Cutting-Edge Controls Available in Open Access Quantum Computing Testbed
AQT has built a multidisciplinary team focused on the design, fabrication, and operation of superconducting quantum processors. For the development of the full control stack, AQT partners with companies, such as Zurich Instruments, for commercial control solutions, consisting of classical electronics, firmware, and software to enable the execution of quantum algorithms. In parallel, AQT has developed an in-house and open source modular electronics control and measurement system —QubiC — for superconducting quantum processors, making engineering solutions for emerging hardware more accessible. QubiC has been flagged several times as noteworthy in the scientific literature while earning a nomination as a finalist in the 2022 R&D 100 Awards. AQT also collaborates with Fermilab’s open source QICK (Quantum Instrumentation Control Kit) and has contributed to its development as an AQT user project.
“At AQT, we recognize that architecture modularity paves the way to exploration and extensibility, so keeping electronic controls agile and adaptable is vital. There is no clear choice for the perfect controls solution for the near future; such discussions among stakeholders will smoothen the path to convergence in the longer term,” said Nowrouzi.
Since 2020, Berkeley Lab has operated an open-access testbed designed for experiments with external users from academia, the national laboratories, and industry, making these various electronic control tools available to all users. The users’ feedback has, in turn, advanced AQT’s understanding of the varying controls landscape, making AQT uniquely positioned to advance the fundamental exploratory efforts relevant to the scientific mission of DOE with cutting-edge R&D that can transfer from the lab to industry. The testbed has already supported various research projects from academia, national laboratories, and industry executing algorithms for scientific computation, benchmarking the current generation of noisy intermediate-scale quantum hardware, and co-designing next-generation architectures and algorithms.
