When it comes to developing quantum computers and harnessing quantum information, scientists require a complete understanding of the materials that make up superconducting qubits, or quantum bits, the core component of a quantum computer that holds information. Scientists at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, along with collaborators such as Rigetti Computing and the National Institute of Standards and Technology, have used a new technique to identify impurities within physical qubits that can limit the lifespan of quantum information.
Daniel Bafia examines the TOF-SIMS equipment located in a material science laboratory at Fermilab. Use of this equipment has allowed SQMS researchers to study impurities in superconducting qubits at the part per million level. Photo: Reidar Hahn, Fermilab
Quantum decoherence is the phenomenon where noise originating from various factors can limit the lifespan over which quantum information can be stored. This phenomenon adversely affects the performance of quantum computers, which rely on quantum information to perform calculations. When scientists successfully build qubits less impacted by sources of quantum decoherence, the power of quantum computers will be unlocked, and scientists will have a new tool to perform calculations difficult or impossible for classical computers to solve.
Quantum computers are designed to solve problems that require large amounts of memory, and through the use of a quantum mechanical property called superposition, these computers will be able to analyze systems that contain large amounts of data, such as traffic patterns, weather predictions, financial modeling and much more.
“In superconducting qubits, we’ve long wondered what underlying materials properties affect the performance of quantum computers,” said Josh Mutus, director of quantum materials at Rigetti Computing. “Now SQMS researchers have been able to examine Rigetti devices with high-precision analytical equipment in order to uncover potential defect systems that we were never able to explore before.”
Impurities found within materials that comprise superconducting qubits can be attributed to causing quantum decoherence, which scientists at the Fermilab-led Superconducting Quantum Materials and Systems Center have highlighted in a paper published in the Applied Physics Letters journal.
3D representation of hydrocarbon impurity distribution in superconducting qubit samples provided through TOF-SIMS analysis. Photo: SQMS Center
Through a three-dimensional analysis of the qubit at the atomic level, scientists revealed impurities that include elements such as oxygen, hydrogen, carbon, chlorine, fluorine, sodium, magnesium and calcium.
To uncover these impurities, scientists use a device called the TOF-SIMS, or time-of-flight secondary ion mass spectrometer, to rapidly fire ions at a qubit and chip away at it. The ions chipped from the qubit’s surface are analyzed in a sensor in the instrument where the constituent elements can be identified with part per million accuracies.
“Our initial goal, as part of the center, was to identify precisely what is within a qubit sample in terms of impurities and defects. Once we have access to that information, we are then in a solid position to build strategies to remove these impurities and boost performance,” said Akshay Murthy, the primary author of this publication and research associate at the SQMS Center. “This is the sort of information that we need to move to the next step.”
The TOF-SIMS instrument was originally purchased for the superconducting radio frequency research program at Fermilab to identify impurities in accelerator cavities used to push particles in a particle accelerator. Now, for the very first time, the TOF-SIMS device has been used to analyze qubits. Impurities in the materials that make up accelerator cavities also impact performance, which makes this instrument applicable for SQMS scientists who are also identifying impurities in materials that compromise or help other superconducting technologies.
“Our initial goal as part of the center was to identify precisely what it is within the sample in terms of impurities and defects. Once we have access to that information, we are then in a solid position to build strategies to remove these impurities and boost performance,” said Akshay Murthy
“The tools needed to perform this characterization are not only specialized and expensive, but also require experienced scientists to acquire and analyze the data,” said Anthony McFadden, a qubit fabrication expert at NIST. “The collaborations formed within SQMS take advantage of specialized equipment and expertise in place at Fermilab and institutions around the country.”
The TOF-SIMS identifies atoms from the top level and etches away downward through the qubit, generating a three-dimensional profile of the elements and compounds that comprise the qubit and identifying where and what type of impurities are present.
“This work has illuminated some often-overlooked sources of decoherence commonly formed during device-processing,” said McFadden.
Qubits can be made by depositing a layer of superconducting niobium on silicon. Scientists vaporize the niobium into a gas, and just as water vapor forms ice on cold metal during the winter, niobium solidifies and forms a film on top of the silicon.
Murthy said that the original chamber for integrating the niobium, or the configuration of the niobium atoms on the film, might contribute to impurities on the qubit. Analysis from the TOF-SIMS can be used to refine the process for creating qubits from a materials and method point of view.
U.S. Department of Energy Chief Commercialization Officer and Director of the Office of Technology Transfers Vanessa Chan tours Fermilab with James Fritz (right), senior advisor for OTTE and Fermilab Chief Technology Officer Alex Romanenko (center). During the visit, the group spoke with Akshay Murthy (left) and Daniel Bafia regarding materials research, use of the TOF-SIMS equipment and technology transfer opportunities within SQMS. Photo: Ryan Postel, Fermilab
The TOF-SIMS setup at Fermilab not only identifies impurities, but it also has a treatment chamber used to heat different materials and change parameters to help scientists study the qubit’s chemical composition and furthermore, mimic fabrication processes.
“By having access to this additional treatment chamber, we can now perform a treatment and then directly analyze and assess its impact on the structure and resultant properties of the sample,” said Murthy.
The next steps are to quantify the effects of sources of decoherence and to engineer processes that avoid these effects altogether.
“Through analyzing qubits with our TOF-SIMS setup, we are now able to examine each step in the fabrication process to identify when impurities become present,” said Alexander Romanenko, Fermilab’s chief technology officer and head of the Applied Physics and Superconducting Technology Division. “Fermilab is the world expert on superconducting technologies for particle accelerators, and through sharing facilities and expertise at the lab with our SQMS partners, we hope to play an integral role in providing the world with the next leap in computing. Our facilities allow us to conduct world-class research on the materials that further the field of quantum information sciences.”
The Superconducting Quantum Materials and Systems Center is one of the five U.S. Department of Energy National Quantum Information Science Research Centers. Led by Fermi National Accelerator Laboratory, SQMS is a collaboration of 21 partner institutions—national labs, academia and industry—working together to bring transformational advances in the field of quantum information science. The center leverages Fermilab’s expertise in building complex particle accelerators to engineer multiqubit quantum processor platforms based on state-of-the-art qubits and superconducting technologies. Working hand in hand with embedded industry partners, SQMS will build a quantum computer and new quantum sensors at Fermilab, which will open unprecedented computational opportunities. For more information, please visit https://sqms.fnal.gov.
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.
Fans of the Fermilab bison herd, rejoice: Fermilab has installed a web camera in the laboratory’s bison pasture. Now you can watch the storied herd 24 hours a day, seven days a week.
A fresh perspective: Fermilab’s new bison camera will now enable viewers to see the bison at any time of day, seven days a week. Photo: Fermilab
The first bison herd at the U.S. Department of Energy’s Fermi National Accelerator Laboratory was introduced to the grounds in 1969. It consisted of a bull and four cows. Today, the herd comprises nearly 30 bison.
Since their arrival, countless visitors have come to Fermilab to see the animals. The birth of the season’s first baby bison calves always makes the local news and is a proud moment for the lab. In 2015, former Fermilab ecologist Ryan Campbell received results from a genetic study that concluded the lab’s herd was 100% bison, with no evidence of cattle genes. And in 2016, bison were declared the national mammal of the United States through the National Bison Legacy Act.
In 2016, bison were declared the national mammal of the United States through the National Bison Legacy Act.
The new Fermilab bison cam provides multi-directional camera capability and offers an image of the herd that’s updated every 15 minutes. To see a new view, viewers should refresh their browsers, use the arrows to select a different perspective, or choose the time-lapses option that provides a glimpse into the herd’s activity at quarter-of-the-hour intervals throughout the day. With the new webcam, viewers offsite now will be able to watch the bison feed, sleep, walk and shake off snow. Viewers can also observe other remarkable behaviors, such as moments when the dominant female leads the herd out to pasture to graze. If fans are lucky, they may even get to see a bison give birth this April through May.
Every spring, new bison calves are born on the Fermilab grounds. Webcam visitors can now get a view of the herd and track the new additions as they arrive. Photo: William Alvarez, Fermilab
“We’re thrilled to provide this window into the lives of our bison herd, their habits and movements,” said Maureen Hix of the Fermilab Education and Public Engagement Office. “These impressive, magnificent creatures have been part of the lab’s history and reflect the amazing legacy of Indigenous people. They are wonderful to see in-person, but the next best thing is to watch them in real time on your screen. We hope that viewers will enjoy this opportunity to bring these amazing animals into their homes!”
Check out the bison through Fermilab’s new bison cam.
Fermi National Accelerator Laboratory and its ecology and wildlife efforts are 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.
The U.S. Department of Energy’s Fermi National Accelerator Laboratory signed a project planning document with the Wrocław University of Science and Technology in Poland. With the signing, WUST officially joined the global collaboration working on Fermilab’s Proton Improvement Plan-II, known as the PIP-II project.
PIP-II is an upgrade of Fermilab’s accelerator complex that includes a new linear accelerator. It is an essential enhancement that will power the world’s most intense high-energy neutrino beam for the international Deep Underground Neutrino Experiment at the Long-Baseline Neutrino Facility hosted by Fermilab. PIP-II will provide the international particle physics community with a world-class scientific facility that will enable discovery-focused research, transform our understanding of nature and strengthen the connection between advances in fundamental science and technology innovation.
Rector Professor Arkadiusz Wójs, Wrocław University of Science and Technology, and Fermilab Director Nigel Lockyer signed the project planning document for work on the PIP-II particle accelerator project.
WUST joins a long list of PIP-II’s global collaborators that includes 11 institutions in France, India, Italy, Poland and the United Kingdom as well as four national labs. Funded primarily by the U.S. Department of Energy, PIP-II is the first particle accelerator built in the United States with significant contributions from international partners.
WUST’s contributions to PIP-II build upon the university’s expertise in cryogenics and next-generation superconducting accelerator technologies—key components to PIP-II’s superconducting linear accelerator. Having previously contributed to the European X-FEL and European Spallation Source projects, WUST plans to contribute design and hardware for the cryogenic transfer lines for the 215-meter-long PIP-II accelerator.
“WUST has a longstanding record of successful contribution to international scientific projects around the world,” said Arkadiy Klebaner, PIP-II technical director. “We are grateful to our Polish partners for their world-class expertise, contribution and support in building a state-of-the-art particle accelerator that will power the neutrino beam for DUNE and enable scientific discoveries for decades to come.”
“The cryogenic team at WUST is highly motivated to contribute to the PIP-II accelerator,” said Professor Maciej Chorowski, initiator of the university’s involvement in the development of the PIP-II cryogenic system. “We appreciate both the technical challenge and the international character of this prestigious project.”
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.