Just as the sound of a guitar depends on its strings and the materials used for its body, the performance of a quantum computer depends on the composition of its building blocks. Arguably the most critical components are the devices that encode information in quantum computers.
One such device is the transmon qubit — a patterned chip made of metallic niobium layers on top of a substrate, such as silicon. Between the two materials resides an ultrathin layer that contains both niobium and silicon. The compounds of this layer are known as silicides (NbxSiy). Their impact on the performance of transmon qubits has not been well understood — until now.
The silicide research team. In the front from left to right: Mark Hersam, Michael Bedzyk, James Ronidnelli and Xiezeng Lu. Back: Carlos Torres and Dominic Goronzy. Photo: SQMS Center
Silicides form when elemental niobium is deposited onto silicon during the fabrication process of a transmon qubit. They need to be well understood to make devices that reliably and efficiently store quantum information for as long as possible.
Researchers at the Superconducting Quantum Materials and Systems Center, hosted by the U.S. Department of Energy’s Fermi National Accelerator Laboratory, have discovered how silicides impact the performance of transmon qubits. Their research has been published in APS Physical Review Materials.
An unexpected signal
Carlos Torres-Castanedo was analyzing the materials of a transmon qubit using x-rays, when he came across a peculiar signal.
“I thought the signal came from a surface oxide, because that’s just what usually happens,” said Torres-Castanedo, a doctoral candidate in materials science at Northwestern University. “After spending a day trying to fit the data to match an oxide, the only possibility was to introduce a niobium silicide layer. When the data beautifully fit the model, I showed the results to my co-workers, and we all became excited about what this could mean for transmon qubit performance.”
The SQMS Center researchers dug deeper. They identified the types of silicides present, the thickness of the layer — typically only a few nanometers thick — and its physical and chemical structure. After completing these measurements, they focused on figuring out how these compounds affect the performance of qubits.
The researchers simulated different types of silicides. Not only did they find that silicides are detrimental to the performance of transmon qubits, but they also found that some are more detrimental than others.
Impact on coherence time
Qubits are the basic and fragile units of information that a quantum computer uses to perform calculations. They are physically encoded through transmon qubits.
Similar to a street performer plucking an A note on a guitar string and allowing the tone to ring out before it becomes obscured by street noise, quantum information in a transmon qubit exists for a limited time before it dissipates or is obscured by environmental noise. This time span is known as the coherence time. The longer the coherence time, the better the performance of the transmon qubit.
“This interface will never be like silicon stop, niobium start,” said SQMS Center researcher James Rondinelli, Walter Dill Scott Professor of Materials Science and Engineering at Northwestern University. “The first observation was that there is not an atomically sharp interface, but rather a compositional gradient between the silicon substrate —which is the platform for the system — and the niobium.”
With that observation, Rondinelli and his group began a detailed computational study as part of a greater SQMS Center effort to improve qubit coherence times.
Simulations with a supercomputer
With a newfound curiosity about what the presence of silicides could mean for transmon qubits, the researchers used a supercomputer at the National Energy Research Scientific Computing Center, located at the DOE’s Lawrence Berkley National Laboratory.
Think of silicides as a thin material inside the street performer’s guitar that affects the sound of the guitar string. Researchers studying transmon qubits are essentially trying to isolate an A note and seeing to what extent the hidden material interferes.
Some silicides, for example, have magnetic properties that can interfere with the quantum information that rings out from the transmon qubit. The stronger the magnetism, the more the quantum information is obscured.
Through simulations, researchers found that the silicide compound Nb6Si5 does not have any magnetic properties, while Nb5Si3 introduces magnetic noise. If silicides will always be present in transmon qubits, whether researchers like it or not, Nb6Si5 is less detrimental, and scientists will have to make do.
“To really push the field forward, you have to embrace a little bit of an outsider perspective to make an advancement, and we’re optimistic our multidisciplinary approach will solve this challenge.” – James Rondinelli, SQMS Center researcher
“I find it interesting how the research on the properties of these silicides have been studied since the ’80s, but never have been understood in a nanometer-sized film,” said Torres-Castanedo. “I feel proud that I was able to work alongside my fellow researchers to conduct this important study.”
These findings by themselves are significant. In the greater context of the SQMS Center’s aim to develop a state-of-the-art quantum computer, however, the results have much further implications than just understanding the properties of materials.
“The community who’s worked on superconducting qubits has traditionally been quantum physicists and engineers. The reason the SQMS Center has been so successful is they’ve embraced material scientists,” said Rondinelli. “To really push the field forward, you have to embrace a little bit of an outsider perspective to make an advancement, and we’re optimistic our multidisciplinary approach will solve this challenge.”
The Superconducting Quantum Materials and Systems Center at Fermilab is supported by the DOE Office of Science.
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 24 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 sqmscenter.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.
Shown with his 2022 piece, called “Spherical Harmony,” which is made of birch and represents 3D harmonic interactions, Ricardo Mondragon has spent nearly 10 years transferring cosmic music into tangible materials. He will continue his process with particle physics in Fermilab’s 2023 artist-in-residence program. Photo: Ricardo Mondragon
Imagine running your fingers along a standing wave’s oscillating momentum and feeling a powerful sensation that your brain tries to interpret. As you touch “Cubic Entanglement” — a visual representation of a stationary wave’s harmonies — your eyes also marvel at how universal sounds could translate into a physical piece of art. The transfer of music to art is an example of Ricardo Mondragon’s life work, an opus that he will now continue at the U.S. Department of Energy’s Fermi National Laboratory as the lab’s 2023 artist-in-residence.
Mondragon is a visual artist who takes inspiration from harmonies in physics and transforms them into materials. He translates frequencies, vibrations and rhythms into visual works of art, such as a sculpture, paintings or installations. Born and raised in Mexico City with an interest in the arts, Mondragon eventually graduated with a Bachelor of Arts in Music Composition from Columbia College Chicago. He has exhibited his work at the Hyde Park Art Center and the Design Museum of Chicago. Mondragon has lectured at places like the Museum of Contemporary Art Chicago and the Chicago Symphony Center. He has also created a live projection for the Louisville Orchestra. For nearly 10 years, the 38-year-old artist has combined the scientific wonders of the world with art.
“Everything that I do involves physics, that’s just part of the process,” said Mondragon. “The main things my work focuses on are harmonies, which happen everywhere. It happens in physics when you align waveforms.”
These waveforms are the foundation Mondragon uses to build his visual masterpieces.
An intricate process
Each of his works displays harmonic interactions, including ratios, intervals, chords, standing waveforms, frequency entanglements, and Chladni forms in three dimensions — a technique discovered by physicist Ernest Chladni that visualizes acoustics when sand moves on a metal plate. In his opinion, one of his strongest pieces is his 2022 piece, called “Cubic Entanglement,” which captures a perfect 3D representation of the Chladni plate. While this piece has a curvilinear internal body with many different facets and intricacies within and outside of it, it serves as a prime example of his previous and future work.
“For me, music is aligned physics. So, when I do a three-dimensional chord with sine waves, they behave in ratios and tonalities that are aligned frequencies,” Mondragon said. “So that’s why music works. It can make harmonic structures look very beautiful to the eye, especially when they don’t have friction.”
“I hope my art helps convey the message that physics is the language of the universe, just like mathematics or music.” – Ricardo Mondragon
Once inspired by a fractal or waveform interactions, Mondragon takes up to a year to create a piece that follows a multi-step process. First, he starts with sculpting and shaping sounds with digital or analog signal processing techniques through waveform generators — a tool that creates electrical waveforms into various wave shapes: sine, pulse, triangular and squares. After this, he hones in on the details of the waveforms, looks for their harmonies, and then transfers them into a three-dimensional shape with various 3D software programs. After creating the digital models and reshaping the files, he will lastly pick the material that best suits how he wants to portray his work, which also dictates how it’s created, via manual tools, 3D printing, routers, cast or any other process that suits the form.
For example, Mondragon created “Harmonic Interactions” with an aluminum material that underwent a manual casting process and handcrafted “Cubic Entanglement” with a CNC machine–generally used for computerized manufacturing processes. Another piece he added to his unique collection was a 3D-printed sculpture called “The Fourth,” from the musical interval.
Art and physics intersect at Fermilab
Initiated by the Fermilab Art Gallery in 2014, the artist-in-residence program is now in its eighth year. The program aims to foster new artists through mentorship and allow them to build new connections to translate a sector of science into creative and inspiring work to share with the public. A committee of seven comprised of scientists, administrators and artists reviews the submitted applications. Initially, in the program’s first year, the committee received 20 submissions, but this year, the application pool grew to 75 submissions.
Handcrafted using a CNC machine, which is generally used for computerized manufacturing processes, “Cubic Entanglement” is a 3D representation of the Chladni plate — a technique discovered by physicist Ernest Chladni that visually demonstrates acoustics when sand moves on a metal plate. Photo: Ricardo Mondragon
“This cross-disciplinary aspect of learning is beneficial because everyone comes from different points of view,” said Georgia Schwender, founder and director of the artist-in-residence program. “Professions can grow by just listening to one another and sharing such work with the community.”
Schwender is most excited to see how Mondragon visualizes particle physics because of the many parallels his past work has with higher-energy physics.
“I just loved his different use of materials and the imagery he does with paper,” she said. “It is so exciting, and I just loved his enthusiasm and his dedication to art and communication.”
From Jan. 1 to Dec. 31, Mondragon will embark on an interdisciplinary journey with the artist-in-residence program that will give him the freedom and creative space to create new work while also helping him to suit his needs.
Currently, the artist is sculpting a piece made of birch wood. He also is working on some large-scale screenprints, which is a common printing process of applying ink to a mesh material. Humbled and excited about his year-long residency, he hopes to follow his heart and speak to the hearts of others.
“I hope my art helps convey the message that physics is the language of the universe, just like mathematics or music,” said Mondragon.
The Fermilab artist-in-residence program is funded by the Fermi Research Alliance.
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.
Deep below the surface in South Dakota, construction crews have been working tirelessly to carve out a network of caverns and tunnels that one day will house a huge neutrino experiment. Their efforts are paying off: With almost 400,000 tons of rock extracted from the earth, the excavation is now half complete.
Once finished, the Long-Baseline Neutrino Facility will be the site of the international Deep Underground Neutrino Experiment. DUNE will focus on studying neutrinos, elusive particles that may hold the answers to many of the universe’s mysteries, such as why our universe is made of matter and how black holes and neutron stars are born. More than 1,000 scientists and engineers from over 30 countries are a part of LBNF/DUNE.
LBNF will provide the space, infrastructure and particle beam for DUNE, hosted by the U.S. Department of Energy’s Fermi National Accelerator Laboratory. It includes underground caverns for a near detector at Fermilab, about 40 miles west of Chicago, and a far detector located 800 miles away at the Sanford Underground Research Facility in South Dakota.
The new underground area at SURF will consist of three large caverns. Two will measure around 500 feet long, 65 feet wide and 90 feet high. These will provide space to house four detector modules — each filled with 17,000 tons of ultrapure liquid argon. The third will be around 625 feet long, 65 feet wide and 36 feet tall and contain cryogenic support systems, detector electronics and data acquisition equipment.
When complete later this year, this cavern will be around 500 feet long, 65 feet wide and 90 feet high. It will be one of three caverns that will provide space to house particle detector modules and other equipment for the Deep Underground Neutrino Experiment. Photo: David Smith, Fermilab
To create these caverns, a total of approximately 800,000 tons of rock will be excavated and moved to the surface. Once complete, the footprint of the underground area with the three caverns will cover about the size of eight soccer fields.
Thyssen Mining Inc., the company contracted to carry out the excavation, began the underground work at SURF in 2021. This January, construction crews reached a critical milestone: 50% completion.
“We have excavated roughly 395,000 tons,” said Ryan Moe, the U.S. general manager at Thyssen Mining. “It’s going well.”
Careful, painstaking work
The first half of the excavation involved several important steps: mobilizing large equipment underground; creating a ventilation shaft; carefully creating a network of tunnels known as drifts; and excavating enormous caverns.
Moving all the necessary equipment underground was no simple task. It involved taking the underground construction mining equipment apart, lowering the parts a mile below the ground through a narrow shaft, then reassembling the construction machinery underground. It was a process that “required a lot of time,” said Michael Gemelli, the LBNF Far-Site Conventional Facilities project manager.
“We have excavated roughly 395,000 tons. It’s going well.” – Ryan Moe, the U.S. general manager at Thyssen Mining
One of the pieces of equipment brought underground was the raise bore machine, which was used to create a ventilation shaft for cooling and airflow to the underground caverns. To create this shaft, workers used the raise bore machine to drill a 13 3/4-inch pilot hole. Then, they attached a 12-foot-diameter reamer head to the drill stem and back-reamed the pilot hole to form a raise bore hole that is 1,200 feet in height.
Once the equipment was underground, construction crews began excavating the drifts, an interconnecting highway of tunnels that connect the three caverns. To form these underground tunnels, the miners used the drill-and-blast technique, which involves drilling a series of holes, then filling those holes with explosives to blast away the rock.
Caverns begin to take shape
Construction crews now are in the process of excavating the caverns using the drill-and-blast method. An important milestone during this first half of the excavation was the completion of the caverns’ top headings: dome-shaped upper sections of each of the caverns.
When forming the cavern top headings, the contractor had to execute this work methodically, said Gemelli. It involves initially excavating a small pilot tunnel to assess the geology and ground water conditions, then enlarge the sides to create the full span of the caverns. “This type of intensive mining required a lot of different steps to support the ground during excavation,” Gemelli added.
Following the excavation, workers installed steel monorail beams in the caverns to accommodate the cranes that will later be used to erect scientific equipment. They also reinforced both the drifts and cavern top headings with ground support anchors, wire mesh and sprayed concrete.
Almost 800,000 tons of rock need to be excavated to create the space for the South Dakota portion of the Deep Underground Neutrino Experiment. Half of the excavation is now complete. Graphic: Fermilab
Safety first
Currently, 145 people from Thyssen work on site at SURF. The operations team, which works underground each day, consists of roughly 115 people. The rest includes engineers and administrative staff working on the surface.
The Thyssen team has successfully reached the halfway point of the excavation while maintaining an excellent standard of safety.
“Our safety record underground has been very good, and we would like to continue to the end of the project with nobody getting hurt,” said Moe. “Second to safety is to deliver a high-quality project, and everybody’s been happy with the quality of the work that we’ve done.”
Accelerating forward
The completion of the top headings sets the stage for the next phase of the excavation, which will involve drilling and blasting downward from those headings to carve out the rest of the caverns. “The last half of the project is all about excavating these three caverns,” Gemelli said. “This will be the peak period of rock excavation.”
Teams will also pour concrete floors in the base of the caverns and in all the interconnecting drifts. Once that’s complete, they will move the construction machinery out of the caverns — a process that will require first breaking down the equipment into smaller pieces, then sending the components up through the shaft to the surface.
This last half of the excavation will move much faster than the first half, according to Gemelli. The second phase of the excavation is now in full swing and is expected to be complete in 2024. “The hardest part of this project is now over with,” Gemelli said. “But we’ve still got a lot to do.”
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.
After finding a passion for the power of sound and the beauty of science in his youth, Roger Zare has been selected as Fermilab’s 2023 guest composer. Photo: Roger Zare
The artist behind the tonal landscape of the “Green Flash” and the rhythmic exuberance of “Far from Equilibrium” is the U.S. Department of Energy’s Fermi National Accelerator Laboratory’s 2023 guest composer Roger Zare.
Currently living in Boone, North Carolina, Zare creates compositions for full orchestras, wind ensembles and single instruments, while serving as a visiting assistant professor of music at the Hayes School of Music at Appalachian State University. He previously served as an instructional assistant professor of theory and composition at Illinois State University.
Awarded for a variety of his work, Zare has even taken part in a workshop hosted by CERN at the Montreux Jazz Festival, where he presented as part of a session, titled “The Physics of Music and The Music of Physics.” A performance at CERN of his piece, “LHC,” performed by the award-winning Donald Sinta Saxophone Quartet, followed. The four movements of the piece explore different aspects of particle physics, from the duality of quark pairs to the energy in the beams of the LHC at that time, Zare said.
Instantly enamored by the beautiful sounds of the piano and violin in his youth, Zare continued his journey in music by producing more than 80 compositions — half of which are about science — over the course of his 37 years. His intersectional work translates concepts of higher-energy physics into the language of music to compose work that translates scientific concepts into music while still remaining accessible to the audience. Such work has allowed him to invent compositions that speak to other people as well as his own heart.
“I love the mind-blowing nature of what science is – where it is able to describe things that we’re almost unable to touch ourselves and explain things in the universe,” said Zare. “I’m excited by these big concepts in science, such as subatomic particles, and I can express my excitement through music.”
While Zare isn’t a scientist himself, he appreciates the complexity of physics; he will study certain topics in the field that serve as inspiration for his pieces so he can have a keener understanding. For instance, Zare’s piece called “Far from Equilibrium” was a collaboration between the composer, Chicago-based astrophysicist Elizabeth Hicks and choreographer Megan Rhyme. They helped guide his understanding, and the resulting composition focuses on the physics of turbulence. He said the piece touched on ideas of the chaos theory to the energy cascade of fluid particles as they progress toward turbulence.
“I experimented with unusual temporal notation to create unpredictable musical effects that represented the physics about which I was learning,” Zare said. “Working on this project was one of the most engaging and enlightening experiences I have had, and it continues to inform how I approach composition to this day.”
Zare was one of the 70 applicants from around the world who applied for Fermilab’s year-long guest composer program. The program enables Fermilab physicists and one composer to collaborate and bridge music and physics; ultimately, it’s intended to inspire people and, through the music created during the residency, help them appreciate science from a different perspective. Now in its third year, the program provides composers the means to build their contacts and communicate the science conducted at Fermilab.
“This program is a unique way to share the synergies and creativity that are common to both art or music and science, and to use music and art as a way to explore and communicate some of the scientific principles, experiments and work that we have going on at Fermilab,” said Janet MacKay-Galbraith, director of the guest composer program. “There are so many commonalities between science, music and art.”
“Hopefully, my work connects to people who aren’t necessarily scientists and helps inform them about some part of nature or the universe that they didn’t know about before.” – Roger Zare
For the guest composer selection process, a five-person committee with scientists, administrators and artists evaluate each applicant’s submission packets. Each packet will include a composer’s resume, two to three letters of recommendations, work samples and a statement of intent. One of the key factors the committee keeps in mind when reviewing submissions, MacKay-Galbraith said, is that the science explored is “represented appropriately and definitively.” In 2023, the program will run from Jan. 1 to Dec. 31.
“Roger had a remarkable statement of intent with a deep affinity for writing music about science. He had a very clear idea of what he wanted to compose, and what he needed to do to execute it,” MacKay-Galbraith said. “One of the things that Roger had that was very interesting to us was that in addition to his catalog of science-inspired work, he has created compositions for small and large chamber ensembles, which allows some flexibility in trying to figure out how to best showcase his role.”
Another source of inspiration for Zare is the DUNE detector that’s currently under construction. The way physicists study neutrinos and even the size of the future detector fascinate the composer. Because he sees music in a visual way, Zare tries to make musical shapes that reflect something in the world. During his residency with Fermilab, he hopes to create a musical story that imagines a journey a neutrino might take before reaching the neutrino experiment’s detector.
“The opening of the work will be chaotic and violent, representing the collapsing star. A middle section will represent the neutrino’s journey at the speed of light with paradoxical tempos occurring simultaneously – the neutrino is moving at the incredibly fast speed limit of the universe, but from our frame of reference, its time is essentially standing still,” Zare said. “The final section will represent the DUNE detector with grandiose music, eventually retracting into sparse flickers of sound that represent the occasional neutrinos interacting with it.”
Embracing the notion that music can communicate and even foster scientific understanding, Zare hopes his residency at Fermilab helps educate people about science and enrich their lives through sound.
“Hopefully, my work connects to people who aren’t necessarily scientists and helps inform them about some part of nature or the universe that they didn’t know about before,” said Zare.
The Fermilab composer-in-residence program is funded by the Fermi Research Alliance.
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.