When designing a next-generation quantum computer, a surprisingly large problem is bridging the communication gap between the classical and quantum worlds. Such computers need a specialized control and readout electronics to translate back and forth between the human operator and the quantum computer’s languages — but existing systems are cumbersome and expensive.
However, a new system of control and readout electronics, known as Quantum Instrumentation Control Kit, or QICK, developed by engineers at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, has proved to drastically improve quantum computer performance while cutting the cost of control equipment.
Gustavo Cancelo led a team of Fermilab engineers to create a new compact electronics board: It has the capabilities of an entire rack of equipment that is compatible with many designs of superconducting qubits at a fraction of the cost. Photo: Ryan Postel, Fermilab
“The development of the Quantum Instrumentation Control Kit is an excellent example of U.S. investment in joint quantum technology research with partnerships between industry, academia and government to accelerate pre-competitive quantum research and development technologies,” said Harriet Kung, DOE deputy director for science programs for the Office of Science and acting associate director of science for high-energy physics.
The faster and more cost-efficient controls were developed by a team of Fermilab engineers led by senior principal engineer Gustavo Cancelo in collaboration with the University of Chicago whose goal was to create and test a field-programmable gate array-based (FPGA) controller for quantum computing experiments. David Schuster, a physicist at the University of Chicago, led the university’s lab that helped with the specifications and verification on real hardware.
Most of the current control and readout systems for superconducting quantum computers use off-the-shelf commercial equipment in which researchers must string together a dozen or more expensive components resulting bulky and expensive control systems. Photo: The University of Chicago
“This is exactly the type of project that combines the strengths of a national laboratory and a university,” said Schuster. “There is a clear need for an open-source control hardware ecosystem, and it is being rapidly adopted by the quantum community.”
Engineers designing quantum computers deal with the challenge of bridging the two seemingly incompatible worlds of quantum and classical computers. Quantum computers are based on the counterintuitive, probabilistic rules of quantum mechanics that govern the microscopic world, which enables them to perform calculations that ordinary computers cannot. Because people live in the macroscopic visible world where classical physics reigns, control and readout electronics act as the interpreter connecting these two worlds.
Control electronics use signals from the classical world as instructions for the computer’s quantum bits, or qubits, while readout electronics measure the states of the qubits and convey that information back to the classical world.
One promising technology for quantum computers uses superconducting circuits as qubits. Currently, most control and readout systems for superconducting quantum computers use off-the-shelf commercial equipment not specialized to the task. As a result, researchers often must string together a dozen or more expensive components. The cost can quickly add up to tens of thousands of dollars per qubit, and the large size of these systems creates more problems.
Despite recent technological advances, qubits still have a relatively short lifetime, generally a fraction of a millisecond, after which they generate errors. “When you work with qubits, time is critical. Classical electronics take time to respond to the qubits, limiting the performance of the computer,” said Cancelo.
Just as the effectiveness of an interpreter depends on rapid communication, the effectiveness of a control and readout system depends on its turnaround time. And a large system made of many modules means long turnaround times.
To address this issue, Cancelo and his team at Fermilab designed a compact control and readout system. The team incorporated the capabilities of an entire rack of equipment in a single electronics board slightly larger than a laptop. The new system is specialized, yet it is versatile enough to be compatible with many designs of superconducting qubits.
“We are designing a general instrument for a large variety of qubits, hoping to cover those that will be designed six months or a year from now,” Cancelo said. “With our control and readout electronics, you can achieve functionality and performance that is hard or impossible to do with commercial equipment.”
The control and readout of qubits depend on microwave pulses — radio waves at frequencies similar to the signals that carry mobile phone calls and heat up microwave dinners. The Fermilab team’s radio frequency (RF) board contains more than 200 elements: mixers to tweak the frequencies; filters to remove undesired frequencies; amplifiers and attenuators to adjust the amplitude of the signals; and switches to turn signals on and off. The board also contains a low-frequency control to tune certain qubit parameters. Together with a commercial field-programmable gate array, or FPGA, board, which serves as the “brains” of the computer, the RF board provides everything scientists need to communicate successfully with the quantum world.
The two compact boards cost about 10 times less to produce than conventional systems. In their simplest configuration, they can control eight qubits. Integrating all the RF components into one board allows for faster, more precise operation as well as real-time feedback and error correction.
“You need to inject signals that are very, very fast and very, very short,” said Fermilab engineer Leandro Stefanazzi, a member of the team. “If you don’t control both the frequency and duration of these signals very precisely, then your qubit won’t behave the way you want.”
Designing the RF board and layout took about six months and presented substantial challenges: adjacent circuit elements had to match precisely so that signals would travel smoothly without bouncing and interfering with each other. Plus, the engineers had to carefully avoid layouts that would pick up stray radio waves from sources like cell phones and WiFi. Along the way, they ran simulations to verify that they were on the right track.
The design is now ready for fabrication and assembly, with the goal of having working RF boards this summer.
Throughout the process, the Fermilab engineers tested their ideas with the University of Chicago. The new RF board is ideal for researchers like Schuster who seek to make fundamental advances in quantum computing using a wide variety of quantum computer architectures and devices.
“I often joke that this one board is going to potentially replace almost all of the test equipment that I have in my lab,” said Schuster. “Getting to team up with people who can make electronics work at that level is incredibly rewarding for us.”
The new compact design of the quantum control system developed by Fermilab and the University of Chicago saves space, is much less expensive and is being quickly adopted by the quantum community. Photo: The University of Chicago
The new system is easily scalable. Frequency multiplexing qubit controls, analogous to sending multiple phone conversations over the same cable, would allow a single RF board to control up to 80 qubits. Thanks to their small size, several dozen boards could be linked together and synchronized to the same clock as part of larger quantum computers. Cancelo and his colleagues described their new system in a paper recently published in the AIP Review of Scientific Instruments.
The Fermilab engineering team has taken advantage of a new commercial FPGA chip, the first to integrate digital-to-analog and analog-to-digital converters directly into the board. It substantially speeds up the process of creating the interface between the FPGA and RF boards, which would have taken months without it. To improve future versions of its control and readout system, the team has started designing its own FPGA hardware.
The development of QICK was supported by QuantISED, the Quantum Science Center (QSC) and later by the Fermilab-hosted Superconducting Quantum Materials and Systems Center (SQMS). The QICK electronics is important for research at the SQMS, where scientists are developing superconducting qubits with long lifetimes. It is also of interest to a second national quantum center where Fermilab plays a key role, the QSC hosted by Oak Ridge National Laboratory.
A low-cost version of the hardware is now available only for universities for educational purposes. “Due to its low cost, it allows smaller institutions to have powerful quantum control without spending hundreds of thousands of dollars,” said Cancelo.
“From a scientific point of view, we are working on one of the hottest topics in physics of the decade as an opportunity,” he added. “From an engineering point of view, what I enjoy is that many areas of electronic engineering need to come together to be able to successfully execute this project.”
Fermi National Accelerator Laboratory is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC, a joint partnership between the University of Chicago and the Universities Research Association, Inc. Visit Fermilab’s website and follow us on Twitter at @Fermilab.
Whether at work or in his personal life, Fermilab ecologist Wally Levernier enjoys the great outdoors. Photo: Wally Levernier
What is your role at the U.S. Department of Energy’s Fermi National Accelerator Laboratory?
I have been the lab ecologist since October 2018. The ecologist at Fermilab has many roles. I am the chair of the Ecological Land Management Committee, which meets monthly and helps direct the ecology at the lab. I coordinate National Environmental Research Park projects at the lab; this is a designation that allows outside environmental researchers to come to Fermilab and study many aspects of the environment. I am also liaison to Fermilab Natural Areas, the organization that helps to monitor and manage the ecology of Fermilab.
On a day-to-day basis, I conduct invasive species control, collect native seed, conduct plant surveys of our natural areas, plan special projects, lead prescribed burns, help coordinate new construction to minimize environmental impacts, lead FNA workdays, work with the education center for educational opportunities. The job is incredibly diverse.
How did you become interested in ecology?
I have been interested in ecology before I knew what ecology was. When I was young, I spent most of my time outdoors chasing frogs, fishing, and gardening with my grandfather. I also went to outdoor camps in grade school over the summer at McHenry County Conservation District.
What do you like best about working at Fermilab?
The natural areas at Fermilab are unique. The history of the prairie restoration is one of the things I like most. Fermilab started prairie restoration in the mid-70s before it was a common practice. I also enjoy working with FNA; they are dedicated to and passionate about restoration and the environment.
What are the projects you’re working on now with Fermilab?
We have planned some special restoration projects with FNA to restore more suitable nesting habitat for rapidly declining grassland and shrubland nesting bird species.
In the Eola Grassland project, we are planning on removing brush in order to create better nesting habitat. These bird species require large areas that have no trees and few shrubs to nest. We are experimenting with different methods — prescribed burning versus frequent mowing — to see if there is a treatment that nesting birds prefer.
In the Sparrow Hedge, which is shrubland by A.E. Sea, we are planning on trying to create a diverse habitat of native shrubs by removing all trees and non-native shrubs. This is very difficult habitat to restore and maintain. This habitat tends to transition between prairie and savanna/woodland so it is difficult to try and make it somewhat static. It is basically a mixture of grasses, sedges and wildflowers with intermixed shrub clumps. These clumps vary in species, size, distance between clumps, etc. to try to accommodate the preferences of many species.
What are FNA workdays?
Fermilab Natural Areas workdays are where members of FNA come on site to assist with natural areas management activities. Each workday is different. During the winter and spring, we tend to conduct invasive bush removal. Summer and fall workdays tend to be a mixture of brush removal and native seed collection; we manage other invasive species as well. It is a great community-building activity.
What’s the most rewarding part of your job?
Knowing that you are working to preserve plant and animal species in the region, many of which are in decline, is rewarding. So is helping people to learn about and become passionate about nature and ecology. We need more people to care about and interact with the environment.
What is the most challenging part of your work?
We are a small group and depend on the support of others to accomplish our goals. We are only able to complete a portion of what needs to be completed.
One way we prioritize is by determining areas of rare plants and animals and work on those areas. We also identify communities that are in better shape and try to preserve those first. Discussion and planning from the ELM committeealso helps to determine priorities.
Does the lab mark any ecological observances?
Yes. Events are held during the week of Earth Day, and all of the topics have relevance to the environment. This year, I led a virtual wildflower walk on Thursday, April 21, where I also discussed the ecology of Fermilab.
Also, in the past, our Roads and Grounds group has held an Arbor Day planting, which occurs during Earth Week. We hope to continue this again next year.
What do you like to do when you are not working?
I enjoy being outdoors. We hike with our dog in local forest preserves. We enjoy traveling and birding. I also enjoy photography.
Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.