Tag Archives: quasiparticles

Microsoft, D-Wave Systems, quantum computing, and quantum supremacy?

Before diving into some of the latest quantum computing doings, here’s why quantum computing is so highly prized and chased after, from the Quantum supremacy Wikipedia entry, Note: Links have been removed,

In quantum computing, quantum supremacy or quantum advantage is the goal of demonstrating that a programmable quantum computer can solve a problem that no classical computer can solve in any feasible amount of time, irrespective of the usefulness of the problem.[1][2][3] The term was coined by John Preskill in 2011,[1][4] but the concept dates to Yuri Manin’s 1980[5] and Richard Feynman’s 1981[6] proposals of quantum computing.

Quantum supremacy and quantum advantage have been mentioned a few times here over the years. You can check my March 6, 2020 posting for when researchers from the University of California at Santa Barbara claimed quantum supremacy and my July 31, 2023 posting for when D-Wave Systems claimed a quantum advantage on optimization problems. I’d understood quantum supremacy and quantum advantage to be synonymous but according the article in Betakit (keep scrolling down to the D-Wave subhead and then, to ‘A controversy of sorts’ subhead in this posting), that’s not so.

The latest news on the quantum front comes from Microsoft (February 2025) and D-Wave systems (March 2025).

Microsoft claims a new state of matter for breakthroughs in quantum computing

Here’s the February 19, 2025 news announcement from Microsoft’s Chetan Nayak, Technical Fellow and Corporate Vice President of Quantum Hardware, Note: Links have been removed,

Quantum computers promise to transform science and society—but only after they achieve the scale that once seemed distant and elusive, and their reliability is ensured by quantum error correction. Today, we’re announcing rapid advancements on the path to useful quantum computing:

  • Majorana 1: the world’s first Quantum Processing Unit (QPU) powered by a Topological Core, designed to scale to a million qubits on a single chip.
  • A hardware-protected topological qubit: research published today in Nature, along with data shared at the Station Q meeting, demonstrate our ability to harness a new type of material and engineer a radically different type of qubit that is small, fast, and digitally controlled.
  • A device roadmap to reliable quantum computation: our path from single-qubit devices to arrays that enable quantum error correction.
  • Building the world’s first fault-tolerant prototype (FTP) based on topological qubits: Microsoft is on track to build an FTP of a scalable quantum computer—in years, not decades—as part of the final phase of the Defense Advanced Research Projects Agency (DARPA) Underexplored Systems for Utility-Scale Quantum Computing (US2QC) program.

Together, these milestones mark a pivotal moment in quantum computing as we advance from scientific exploration to technological innovation.

Harnessing a new type of material

All of today’s announcements build on our team’s recent breakthrough: the world’s first topoconductor. This revolutionary class of materials enables us to create topological superconductivity, a new state of matter that previously existed only in theory. The advance stems from Microsoft’s innovations in the design and fabrication of gate-defined devices that combine indium arsenide (a semiconductor) and aluminum (a superconductor). When cooled to near absolute zero and tuned with magnetic fields, these devices form topological superconducting nanowires with Majorana Zero Modes (MZMs) at the wires’ ends.

Chris Vallance’s February 19, 2025 article for the British Broadcasting Corporation (BBC) news online website provides a description of Microsoft’s claims and makes note of the competitive quantum research environment,

Microsoft has unveiled a new chip called Majorana 1 that it says will enable the creation of quantum computers able to solve “meaningful, industrial-scale problems in years, not decades”.

It is the latest development in quantum computing – tech which uses principles of particle physics to create a new type of computer able to solve problems ordinary computers cannot.

Creating quantum computers powerful enough to solve important real-world problems is very challenging – and some experts believe them to be decades away.

Microsoft says this timetable can now be sped up because of the “transformative” progress it has made in developing the new chip involving a “topological conductor”, based on a new material it has produced.

The firm believes its topoconductor has the potential to be as revolutionary as the semiconductor was in the history of computing.

But experts have told the BBC more data is needed before the significance of the new research – and its effect on quantum computing – can be fully assessed.

Jensen Huang – boss of the leading chip firm, Nvidia – said in January he believed “very useful” quantum computing would come in 20 years.

Chetan Nayak, a technical fellow of quantum hardware at Microsoft, said he believed the developments would shake up conventional thinking about the future of quantum computers.

“Many people have said that quantum computing, that is to say useful quantum computers, are decades away,” he said. “I think that this brings us into years rather than decades.”

Travis Humble, director of the Quantum Science Center of Oak Ridge National Laboratory in the US, said he agreed Microsoft would now be able to deliver prototypes faster – but warned there remained work to do.

“The long term goals for solving industrial applications on quantum computers will require scaling up these prototypes even further,” he said.

While rivals produced a steady stream of announcements – notably Google’s “Willow” at the end of 2024 – Microsoft seemed to be taking longer.

Pursuing this approach was, in the company’s own words, a “high-risk, high-rewards” strategy, but one it now believes is going to pay off.

If you have the time, do read Vallance’s February 19, 2025 article.

The research paper

Purdue University’s (Indiana, US) February 25, 2025 news release on EurekAlert announces publication of the research, Note: Links have been removed,

Microsoft Quantum published an article in Nature on Feb. 19 [2025] detailing recent advances in the measurement of quantum devices that will be needed to realize a topological quantum computer. Among the authors are Microsoft scientists and engineers who conduct research at Microsoft Quantum Lab West Lafayette, located at Purdue University. In an announcement by Microsoft Quantum, the team describes the operation of a device that is a necessary building block for a topological quantum computer. The published results are an important milestone along the path to construction of quantum computers that are potentially more robust and powerful than existing technologies.

“Our hope for quantum computation is that it will aid chemists, materials scientists and engineers working on the design and manufacturing of new materials that are so important to our daily lives,” said Michael Manfra, scientific director of Microsoft Quantum Lab West Lafayette and the Bill and Dee O’Brien Distinguished Professor of Physics and Astronomy, professor of materials engineering, and professor of electrical and computer engineering at Purdue. “The promise of quantum computation is in accelerating scientific discovery and its translation into useful technology. For example, if quantum computers reduce the time and cost to produce new lifesaving therapeutic drugs, that is real societal impact.” 

The Microsoft Quantum Lab West Lafayette team advanced the complex layered materials that make up the quantum plane of the full device architecture used in the tests. Microsoft scientists working with Manfra are experts in advanced semiconductor growth techniques, including molecular beam epitaxy, that are used to build low-dimensional electron systems that form the basis for quantum bits, or qubits. They built the semiconductor and superconductor layers with atomic layer precision, tailoring the material’s properties to those needed for the device architecture.

Manfra, a member of the Purdue Quantum Science and Engineering Institute, credited the strong relationship between Purdue and Microsoft, built over the course of a decade, with the advances conducted at Microsoft Quantum Lab West Lafayette. In 2017 Purdue deepened its relationship with Microsoft with a multiyear agreement that includes embedding Microsoft employees with Manfra’s research team at Purdue.

“This was a collaborative effort by a very sophisticated team, with a vital contribution from the Microsoft scientists at Purdue,” Manfra said. “It’s a Microsoft team achievement, but it’s also the culmination of a long-standing partnership between Purdue and Microsoft. It wouldn’t have been possible without an environment at Purdue that was conducive to this mode of work — I attempted to blend industrial with academic research to the betterment of both communities. I think that’s a success story.”

Quantum science and engineering at Purdue is a pillar of the Purdue Computes initiative, which is focused on advancing research in computing, physical AI, semiconductors and quantum technologies.

“This research breakthrough in the measurement of the state of quasi particles is a milestone in the development of topological quantum computing, and creates a watershed moment in the semiconductor-superconductor hybrid structure,” Purdue President Mung Chiang said. “Marking also the latest success in the strategic initiative of Purdue Computes, the deep collaboration that Professor Manfra and his team have created with the Microsoft Quantum Lab West Lafayette on the Purdue campus exemplifies the most impactful industry research partnership at any American university today.”

Most approaches to quantum computers rely on local degrees of freedom to encode information. The spin of an electron is a classic example of a qubit. But an individual spin is prone to disturbance — by relatively common things like heat, vibrations or interactions with other quantum particles — which can corrupt quantum information stored in the qubit, necessitating a great deal of effort in detecting and correcting errors. Instead of spin, topological quantum computers store information in a more distributed manner; the qubit state is encoded in the state of many particles acting in concert. Consequently, it is harder to scramble the information as the state of all the particles must be changed to alter the qubit state.

In the Nature paper, the Microsoft team was able to accurately and quickly measure the state of quasi particles that form the basis of the qubit.

“The device is used to measure a basic property of a topological qubit quickly,” Manfra said. “The team is excited to build on these positive results.”

“The team in West Lafayette pushed existing epitaxial technology to a new state-of-the-art for semiconductor-superconductor hybrid structures to ensure a perfect interface between each of the building blocks of the Microsoft hybrid system,” said Sergei Gronin, a Microsoft Quantum Lab scientist.

“The materials quality that is required for quantum computing chips necessitates constant improvements, so that’s one of the biggest challenges,” Gronin said. “First, we had to adjust and improve semiconductor technology to meet a new level that nobody was able to achieve before. But equally important was how to create this hybrid system. To do that, we had to merge a semiconducting part and a superconducting part. And that means you need to perfect the semiconductor and the superconductor and perfect the interface between them.”

While work discussed in the Nature article was performed by Microsoft employees, the exposure to industrial-scale research and development is an outstanding opportunity for Purdue students in Manfra’s academic group as well. John Watson, Geoffrey Gardner and Saeed Fallahi, who are among the coauthors of the paper, earned their doctoral degrees under Manfra and now work for Microsoft Quantum at locations in Redmond, Washington, and Copenhagen, Denmark. Most of Manfra’s former students now work for quantum computing companies, including Microsoft. Tyler Lindemann, who works in the West Lafayette lab and helped to build the hybrid semiconductor-superconductor structures required for the device, is earning a doctoral degree from Purdue under Manfra’s supervision.

“Working in Professor Manfra’s lab in conjunction with my work for Microsoft Quantum has given me a head start in my professional development, and been fruitful for my academic work,” Lindemann said. “At the same time, many of the world-class scientists and engineers at Microsoft Quantum have some background in academia, and being able to draw from their knowledge and experience is an indispensable resource in my graduate studies. From both perspectives, it’s a great opportunity.”

Here’s a link to and a citation for the paper,

Interferometric single-shot parity measurement in InAs–Al hybrid devices by Microsoft Azure Quantum, Morteza Aghaee, Alejandro Alcaraz Ramirez, Zulfi Alam, Rizwan Ali, Mariusz Andrzejczuk, Andrey Antipov, Mikhail Astafev, Amin Barzegar, Bela Bauer, Jonathan Becker, Umesh Kumar Bhaskar, Alex Bocharov, Srini Boddapati, David Bohn, Jouri Bommer, Leo Bourdet, Arnaud Bousquet, Samuel Boutin, Lucas Casparis, Benjamin J. Chapman, Sohail Chatoor, Anna Wulff Christensen, Cassandra Chua, Patrick Codd, William Cole, Paul Cooper, Fabiano Corsetti, Ajuan Cui, Paolo Dalpasso, Juan Pablo Dehollain, Gijs de Lange, Michiel de Moor, Andreas Ekefjärd, Tareq El Dandachi, Juan Carlos Estrada Saldaña, Saeed Fallahi, Luca Galletti, Geoff Gardner, Deshan Govender, Flavio Griggio, Ruben Grigoryan, Sebastian Grijalva, Sergei Gronin, Jan Gukelberger, Marzie Hamdast, Firas Hamze, Esben Bork Hansen, Sebastian Heedt, Zahra Heidarnia, Jesús Herranz Zamorano, Samantha Ho, Laurens Holgaard, John Hornibrook, Jinnapat Indrapiromkul, Henrik Ingerslev, Lovro Ivancevic, Thomas Jensen, Jaspreet Jhoja, Jeffrey Jones, Konstantin V. Kalashnikov, Ray Kallaher, Rachpon Kalra, Farhad Karimi, Torsten Karzig, Evelyn King, Maren Elisabeth Kloster, Christina Knapp, Dariusz Kocon, Jonne V. Koski, Pasi Kostamo, Mahesh Kumar, Tom Laeven, Thorvald Larsen, Jason Lee, Kyunghoon Lee, Grant Leum, Kongyi Li, Tyler Lindemann, Matthew Looij, Julie Love, Marijn Lucas, Roman Lutchyn, Morten Hannibal Madsen, Nash Madulid, Albert Malmros, Michael Manfra, Devashish Mantri, Signe Brynold Markussen, Esteban Martinez, Marco Mattila, Robert McNeil, Antonio B. Mei, Ryan V. Mishmash, Gopakumar Mohandas, Christian Mollgaard, Trevor Morgan, George Moussa, Chetan Nayak, Jens Hedegaard Nielsen, Jens Munk Nielsen, William Hvidtfelt Padkar Nielsen, Bas Nijholt, Mike Nystrom, Eoin O’Farrell, Thomas Ohki, Keita Otani, Brian Paquelet Wütz, Sebastian Pauka, Karl Petersson, Luca Petit, Dima Pikulin, Guen Prawiroatmodjo, Frank Preiss, Eduardo Puchol Morejon, Mohana Rajpalke, Craig Ranta, Katrine Rasmussen, David Razmadze, Outi Reentila, David J. Reilly, Yuan Ren, Ken Reneris, Richard Rouse, Ivan Sadovskyy, Lauri Sainiemi, Irene Sanlorenzo, Emma Schmidgall, Cristina Sfiligoj, Mustafeez Bashir Shah, Kevin Simoes, Shilpi Singh, Sarat Sinha, Thomas Soerensen, Patrick Sohr, Tomas Stankevic, Lieuwe Stek, Eric Stuppard, Henri Suominen, Judith Suter, Sam Teicher, Nivetha Thiyagarajah, Raj Tholapi, Mason Thomas, Emily Toomey, Josh Tracy, Michelle Turley, Shivendra Upadhyay, Ivan Urban, Kevin Van Hoogdalem, David J. Van Woerkom, Dmitrii V. Viazmitinov, Dominik Vogel, John Watson, Alex Webster, Joseph Weston, Georg W. Winkler, Di Xu, Chung Kai Yang, Emrah Yucelen, Roland Zeisel, Guoji Zheng & Justin Zilke. Nature 638, 651–655 (2025). DOI: https://doi.org/10.1038/s41586-024-08445-2 Published online: 19 February 2025 Issue Date: 20 February 2025

This paper is open access. Note: I usually tag all of the authors but not this time.

Controversy over this and previous Microsoft quantum computing claims

Elizabeth Hlavinka’s March 17, 2025 article for Salon.com provides an overview, Note: Links have been removed,

The matter making up the world around us has long-since been organized into three neat categories: solids, liquids and gases. But last month [February 2025], Microsoft announced that it had allegedly discovered another state of matter originally theorized to exist in 1937. 

This new state of matter called the Majorana zero mode is made up of quasiparticles, which act as their own particle and antiparticle. The idea is that the Majorana zero mode could be used to build a quantum computer, which could help scientists answer complex questions that standard computers are not capable of solving, with implications for medicine, cybersecurity and artificial intelligence.

In late February [2025], Sen. Ted Cruz presented Microsoft’s new computer chip at a congressional hearing, saying, “Technologies like this new chip I hold in the palm of my hand, the Majorana 1 quantum chip, are unlocking a new era of computing that will transform industries from health care to energy, solving problems that today’s computers simply cannot.”

However, Microsoft’s announcement, claiming a “breakthrough in quantum computing,” was met with skepticism from some physicists in the field. Proving that this form of quantum computing can work requires first demonstrating the existence of Majorana quasiparticles, measuring what the Majorana particles are doing, and creating something called a topological qubit used to store quantum information.

But some say that not all of the data necessary to prove this has been included in the research paper published in Nature, on which this announcement is based. And due to a fraught history of similar claims from the company being disputed and ultimately rescinded, some are extra wary of the results. [emphasis mine]

It’s not the first time Microsoft has faced backlash from presenting findings in the field. In 2018, the company reported that they had detected the presence of Majorana zero-modes in a research paper, but it was retracted by Nature, the journal that published it after a report from independent experts put their findings under more intense scrutiny.

In the [2018] report, four physicists not involved in the research concluded that it did not appear that Microsoft had intentionally misrepresented the data, but instead seemed to be “caught up in the excitement of the moment [emphasis mine].”

Establishing the existence of these particles is extremely complex in part because disorder in the device can create signals that mimic these quasiparticles when they are not actually there. 

Modern computers in use today are encoded in bits, which can either be in a zero state (no current flowing through them), or a one state (current flowing.) These bits work together to send information and signals that communicate with the computer, powering everything from cell phones to video games.

Companies like Google, IBM and Amazon have invested in designing another form of quantum computer that uses chips built with “qubits,” or quantum bits. Qubits can exist in both zero and one states at the same time due to a phenomenon called superposition. 

However, qubits are subject to external noise from the environment that can affect their performance, said Dr. Paolo Molignini, a researcher in theoretical quantum physics at Stockholm University.

“Because qubits are in a superposition of zero and one, they are very prone to errors and they are very prone to what is called decoherence, which means there could be noise, thermal fluctuations or many things that can collapse the state of the qubits,” Molignini told Salon in a video call. “Then you basically lose all of the information that you were encoding.”

In December [2024], Google said its quantum computer could perform a calculation that a standard computer could complete in 10 septillion years — a period far longer than the age of the universe — in just under five minutes.

However, a general-purpose computer would require billions of qubits, so these approaches are still a far cry from having practical applications, said Dr. Patrick Lee, a physicist at the Massachusetts Institute of Technology [MIT], who co-authored the report leading to the 2018 Nature paper’s retraction.

Microsoft is taking a different approach to quantum computing by trying to develop  a topological qubit, which has the ability to store information in multiple places at once. Topological qubits exist within the Majorana zero states and are appealing because they can theoretically offer greater protection against environmental noise that destroys information within a quantum system.

Think of it like an arrow, where the arrowhead holds a portion of the information and the arrow tail holds the rest, Lee said. Distributing information across space like this is called topological protection.

“If you are able to put them far apart from each other, then you have a chance of maintaining the identity of the arrow even if it is subject to noise,” Lee told Salon in a phone interview. “The idea is that if the noise affects the head, it doesn’t kill the arrow and if it affects only the tail it doesn’t kill your arrow. It has to affect both sides simultaneously to kill your arrow, and that is very unlikely if you are able to put them apart.”

… Lee believes that even if the data doesn’t entirely prove that topological qubits exist in the Majorana zero-state, it still represents a scientific advancement. But he noted that several important issues need to be solved before it has practical implications. For one, the coherence time of these particles — or how long they can exist without being affected by environmental noise — is still very short, he explained.

“They make a measurement, come back, and the qubit has changed, so you have lost your coherence,” Lee said. “With this very short time, you cannot do anything with it.”

“I just wish they [Microsoft] were a bit more careful with their claims because I fear that if they don’t measure up to what they are saying, there might be a backlash at some point where people say, ‘You promised us all these fancy things and where are they now?’” Molignini said. “That might damage the entire quantum community, not just themselves.”

Iif you have the time, please read Hlavinka’s March 17, 2025 article in its entirety .

D-Wave Quantum Systems claims quantum supremacy over real world problem solution

A March 15, 2025 article by Bob Yirka for phys.org announces the news from D-Wave Quantum Systems. Note: The company, which had its headquarters in Canada (Burnaby, BC) now seems to be a largely US company with its main headquarters in Palo Alto, California and an ancillary or junior (?) headquarters in Canada, Note: A link has been removed,

A team of quantum computer researchers at quantum computer maker D-Wave, working with an international team of physicists and engineers, is claiming that its latest quantum processor has been used to run a quantum simulation faster than could be done with a classical computer.

In their paper published in the journal Science, the group describes how they ran a quantum version of a mathematical approximation regarding how matter behaves when it changes states, such as from a gas to a liquid—in a way that they claim would be nearly impossible to conduct on a traditional computer.

Here’s a March 12, 2025 D-Wave Systems (now D-Wave Quantum Systems) news release touting its real world problem solving quantum supremacy,

New landmark peer-reviewed paper published in Science, “Beyond-Classical Computation in Quantum Simulation,” unequivocally validates D-Wave’s achievement of the world’s first and only demonstration of quantum computational supremacy on a useful, real-world problem

Research shows D-Wave annealing quantum computer performs magnetic materials simulation in minutes that would take nearly one million years and more than the world’s annual electricity consumption to solve using a classical supercomputer built with GPU clusters

D-Wave Advantage2 annealing quantum computer prototype used in supremacy achievement, a testament to the system’s remarkable performance capabilities

PALO ALTO, Calif. – March 12, 2025 – D-Wave Quantum Inc. (NYSE: QBTS) (“D-Wave” or the “Company”), a leader in quantum computing systems, software, and services and the world’s first commercial supplier of quantum computers, today announced a scientific breakthrough published in the esteemed journal Science, confirming that its annealing quantum computer outperformed one of the world’s most powerful classical supercomputers in solving complex magnetic materials simulation problems with relevance to materials discovery. The new landmark peer-reviewed paper, Beyond-Classical Computation in Quantum Simulation,” validates this achievement as the world’s first and only demonstration of quantum computational supremacy on a useful problem.

An international collaboration of scientists led by D-Wave performed simulations of quantum dynamics in programmable spin glasses—computationally hard magnetic materials simulation problems with known applications to business and science—on both D-Wave’s Advantage2TM prototype annealing quantum computer and the Frontier supercomputer at the Department of Energy’s Oak Ridge National Laboratory. The work simulated the behavior of a suite of lattice structures and sizes across a variety of evolution times and delivered a multiplicity of important material properties. D-Wave’s quantum computer performed the most complex simulation in minutes and with a level of accuracy that would take nearly one million years using the supercomputer. In addition, it would require more than the world’s annual electricity consumption to solve this problem using the supercomputer, which is built with graphics processing unit (GPU) clusters.

“This is a remarkable day for quantum computing. Our demonstration of quantum computational supremacy on a useful problem is an industry first. All other claims of quantum systems outperforming classical computers have been disputed or involved random number generation of no practical value,” said Dr. Alan Baratz, CEO of D-Wave. “Our achievement shows, without question, that D-Wave’s annealing quantum computers are now capable of solving useful problems beyond the reach of the world’s most powerful supercomputers. We are thrilled that D-Wave customers can use this technology today to realize tangible value from annealing quantum computers.”

Realizing an Industry-First Quantum Computing Milestone
The behavior of materials is governed by the laws of quantum physics. Understanding the quantum nature of magnetic materials is crucial to finding new ways to use them for technological advancement, making materials simulation and discovery a vital area of research for D-Wave and the broader scientific community. Magnetic materials simulations, like those conducted in this work, use computer models to study how tiny particles not visible to the human eye react to external factors. Magnetic materials are widely used in medical imaging, electronics, superconductors, electrical networks, sensors, and motors.

“This research proves that D-Wave’s quantum computers can reliably solve quantum dynamics problems that could lead to discovery of new materials,” said Dr. Andrew King, senior distinguished scientist at D-Wave. “Through D-Wave’s technology, we can create and manipulate programmable quantum matter in ways that were impossible even a few years ago.”

Materials discovery is a computationally complex, energy-intensive and expensive task. Today’s supercomputers and high-performance computing (HPC) centers, which are built with tens of thousands of GPUs, do not always have the computational processing power to conduct complex materials simulations in a timely or energy-efficient manner. For decades, scientists have aspired to build a quantum computer capable of solving complex materials simulation problems beyond the reach of classical computers. D-Wave’s advancements in quantum hardware have made it possible for its annealing quantum computers to process these types of problems for the first time.

“This is a significant milestone made possible through over 25 years of research and hardware development at D-Wave, two years of collaboration across 11 institutions worldwide, and more than 100,000 GPU and CPU hours of simulation on one of the world’s fastest supercomputers as well as computing clusters in collaborating institutions,” said Dr. Mohammad Amin, chief scientist at D-Wave. “Besides realizing Richard Feynman’s vision of simulating nature on a quantum computer, this research could open new frontiers for scientific discovery and quantum application development.” 

Advantage2 System Demonstrates Powerful Performance Gains
The results shown in “Beyond-Classical Computation in Quantum Simulation” were enabled by D-Wave’s previous scientific milestones published in Nature Physics (2022) and Nature (2023), which theoretically and experimentally showed that quantum annealing provides a quantum speedup in complex optimization problems. These scientific advancements led to the development of the Advantage2 prototype’s fast anneal feature, which played an essential role in performing the precise quantum calculations needed to demonstrate quantum computational supremacy.

“The broader quantum computing research and development community is collectively building an understanding of the types of computations for which quantum computing can overtake classical computing. This effort requires ongoing and rigorous experimentation,” said Dr. Trevor Lanting, chief development officer at D-Wave. “This work is an important step toward sharpening that understanding, with clear evidence of where our quantum computer was able to outperform classical methods. We believe that the ability to recreate the entire suite of results we produced is not possible classically. We encourage our peers in academia to continue efforts to further define the line between quantum and classical capabilities, and we believe these efforts will help drive the development of ever more powerful quantum computing technology.”

The Advantage2 prototype used to achieve quantum computational supremacy is available for customers to use today via D-Wave’s Leap™ real-time quantum cloud service. The prototype provides substantial performance improvements from previous-generation Advantage systems, including increased qubit coherence, connectivity, and energy scale, which enables higher-quality solutions to larger, more complex problems. Moreover, D-Wave now has an Advantage2 processor that is four times larger than the prototype used in this work and has extended the simulations of this paper from hundreds of qubits to thousands of qubits, which are significantly larger than those described in this paper.

Leading Industry Voices Echo Support
Dr. Hidetoshi Nishimori, Professor, Department of Physics, Tokyo Institute of Technology:
“This paper marks a significant milestone in demonstrating the real-world applicability of large-scale quantum computing. Through rigorous benchmarking of quantum annealers against state-of-the-art classical methods, it convincingly establishes a quantum advantage in tackling practical problems, revealing the transformative potential of quantum computing at an unprecedented scale.”

Dr. Seth Lloyd, Professor of Quantum Mechanical Engineering, MIT:
Although large-scale, fully error-corrected quantum computers are years in the future, quantum annealers can probe the features of quantum systems today. In an elegant paper, the D-Wave group has used a large-scale quantum annealer to uncover patterns of entanglement in a complex quantum system that lie far beyond the reach of the most powerful classical computer. The D-Wave result shows the promise of quantum annealers for exploring exotic quantum effects in a wide variety of systems.”

Dr. Travis Humble, Director of Quantum Science Center, Distinguished Scientist at Oak Ridge National Laboratory:
“ORNL seeks to expand the frontiers of computation through many different avenues, and benchmarking quantum computing for materials science applications provides critical input to our understanding of new computational capabilities.”

Dr. Juan Carrasquilla, Associate Professor at the Department of Physics, ETH Zürich:
“I believe these results mark a critical scientific milestone for D-Wave. They also serve as an invitation to the scientific community, as these results offer a strong benchmark and motivation for developing novel simulation techniques for out-of-equilibrium dynamics in quantum many-body physics. Furthermore, I hope these findings encourage theoretical exploration of the computational challenges involved in performing such simulations, both classically and quantum-mechanically.”

Dr. Victor Martin-Mayor, Professor of Theoretical Physics, Universidad Complutense de Madrid:
“This paper is not only a tour-de-force for experimental physics, it is also remarkable for the clarity of the results. The authors have addressed a problem that is regarded both as important and as very challenging to a classical computer. The team has shown that their quantum annealer performs better at this task than the state-of-the-art methods for classical simulation.”

Dr. Alberto Nocera, Senior Staff Scientist, The University of British Columbia:
“Our work shows the impracticability of state-of-the-art classical simulations to simulate the dynamics of quantum magnets, opening the door for quantum technologies based on analog simulators to solve scientific questions that may otherwise remain unanswered using conventional computers.”

About D-Wave Quantum Inc.
D-Wave is a leader in the development and delivery of quantum computing systems, software, and services. We are the world’s first commercial supplier of quantum computers, and the only company building both annealing and gate-model quantum computers. Our mission is to help customers realize the value of quantum, today. Our 5,000+ qubit Advantage™ quantum computers, the world’s largest, are available on-premises or via the cloud, supported by 99.9% availability and uptime. More than 100 organizations trust D-Wave with their toughest computational challenges. With over 200 million problems submitted to our Advantage systems and Advantage2™ prototypes to date, our customers apply our technology to address use cases spanning optimization, artificial intelligence, research and more. Learn more about realizing the value of quantum computing today and how we’re shaping the quantum-driven industrial and societal advancements of tomorrow: www.dwavequantum.com.

Forward-Looking Statements
Certain statements in this press release are forward-looking, as defined in the Private Securities Litigation Reform Act of 1995. These statements involve risks, uncertainties, and other factors that may cause actual results to differ materially from the information expressed or implied by these forward-looking statements and may not be indicative of future results. These forward-looking statements are subject to a number of risks and uncertainties, including, among others, various factors beyond management’s control, including the risks set forth under the heading “Risk Factors” discussed under the caption “Item 1A. Risk Factors” in Part I of our most recent Annual Report on Form 10-K or any updates discussed under the caption “Item 1A. Risk Factors” in Part II of our Quarterly Reports on Form 10-Q and in our other filings with the SEC. Undue reliance should not be placed on the forward-looking statements in this press release in making an investment decision, which are based on information available to us on the date hereof. We undertake no duty to update this information unless required by law.

Here’s a link to and a citation for the most recent paper,

Beyond-classical computation in quantum simulation by Andrew D. King , Alberto Nocera, Marek M. Rams, Jacek Dziarmaga, Roeland Wiersema, William Bernoudy, Jack Raymond, Nitin Kaushal, Niclas Heinsdorf, Richard Harris, Kelly Boothby, Fabio Altomare, Mohsen Asad, Andrew J. Berkley, Martin Boschnak, Kevin Chern, Holly Christiani, Samantha Cibere, Jake Connor, Martin H. Dehn, Rahul Deshpande, Sara Ejtemaee, Pau Farre, Kelsey Hamer, Emile Hoskinson, Shuiyuan Huang, Mark W. Johnson, Samuel Kortas, Eric Ladizinsky, Trevor Lanting, Tony Lai, Ryan Li, Allison J. R. MacDonald, Gaelen Marsden, Catherine C. McGeoch, Reza Molavi, Travis Oh, Richard Neufeld, Mana Norouzpour, Joel Pasvolsky, Patrick Poitras, Gabriel Poulin-Lamarre, Thomas Prescott, Mauricio Reis, Chris Rich, Mohammad Samani, Benjamin Sheldan, Anatoly Smirnov, Edward Sterpka, Berta Trullas Clavera, Nicholas Tsai, Mark Volkmann, Alexander M. Whiticar, Jed D. Whittaker, Warren Wilkinson, Jason Yao, T.J. Yi, Anders W. Sandvik, Gonzalo Alvarez, Roger G. Melko, Juan Carrasquilla, Marcel Franz, and Mohammad H. Amin. Science 12 Mar 2025 First Release DOI: 10.1126/science.ado6285

This paper appears to be open access.Note: I usually tag all of the authors but not this time either.

A controversy of sorts

Madison McLauchlan’s March 19, 2025 article for Betakit (website for Canadian Startup News & Tech Innovation), Note: Links have been removed,

Canadian-born company D-Wave Quantum Systems said it achieved “quantum supremacy” last week after publishing what it calls a groundbreaking paper in the prestigious journal Science. Despite the lofty term, Canadian experts say supremacy is not the be-all, end-all of quantum innovation. 

D-Wave, which has labs in Palo Alto, Calif., and Burnaby, BC, claimed in a statement that it has shown “the world’s first and only demonstration of quantum computational supremacy on a useful, real-world problem.”

Coined in the early 2010s by physicist John Preskill, quantum supremacy is the ability of a quantum computing system to solve a problem no classical computer can in a feasible amount of time. The metric makes no mention of whether the problem needs to be useful or relevant to real life. Google researchers published a paper in Nature in 2019 claiming they cleared that bar with the Sycamore quantum processor. Researchers at the University of Science and Technology in China claimed they demonstrated quantum supremacy several times. 

D-Wave’s attempt differs in that its researchers aimed to solve a real-world materials-simulation problem with quantum computing—one the company claims would be nearly impossible for a traditional computer to solve in a reasonable amount of time. D-Wave used an annealing designed to solve optimization problems. The problem is represented like an energy space, where the “lowest energy state” corresponds to the solution. 

While exciting, quantum supremacy is just one metric among several that mark the progress toward widely useful quantum computers, industry experts told BetaKit. 

“It is a very important and mostly academic metric, but certainly not the most important in the grand scheme of things, as it doesn’t take into account the usefulness of the algorithm,” said Martin Laforest, managing partner at Quantacet, a specialized venture capital fund for quantum startups. 

He added that Google and Xanadu’s [Xanadu Quantum Technologies based in Toronto, Canada] past claims to quantum supremacy were “extraordinary pieces of work, but didn’t unlock practicality.” 

Laforest, along with executives at Canadian quantum startups Nord Quantique and Photonic, say that the milestones of ‘quantum utility’ or ‘quantum advantage’ may be more important than supremacy. 

According to Quantum computing company Quera [QuEra?], quantum advantage is the demonstration of a quantum algorithm solving a real-world problem on a quantum computer faster than any classical algorithm running on any classical computer. On the other hand, quantum utility, according to IBM, refers to when a quantum computer is able to perform reliable computations at a scale beyond brute-force classical computing methods that provide exact solutions to computational problems. 

Error correction hasn’t traditionally been considered a requirement for quantum supremacy, but Laforest told BetaKit the term is “an ever-moving target, constantly challenged by advances in classical algorithms.” He added: “In my opinion, some level of supremacy or utility may be possible in niche areas without error correction, but true disruption requires it.”

Paul Terry, CEO of Vancouver-based Photonic, thinks that though D-Wave’s claim to quantum supremacy shows “continued progress to real value,” scalability is the industry’s biggest hurdle to overcome.

But as with many milestone claims in the quantum space, D-Wave’s latest innovation has been met with scrutiny from industry competitors and researchers on the breakthrough’s significance, claiming that classical computers have achieved similar results. Laforest echoed this sentiment.

“Personally, I wouldn’t say it’s an unequivocal demonstration of supremacy, but it is a damn nice experiment that once again shows the murky zone between traditional computing and early quantum advantage,” Laforest said.

Originally founded out of the University of British Columbia, D-Wave went public on the New York Stock Exchange just over two years ago through a merger with a special-purpose acquisition company in 2022. D-Wave became a Delaware-domiciled corporation as part of the deal.

Earlier this year, D-Wave’s stock price dropped after Nvidia CEO Jensen Huang publicly stated that he estimated that useful quantum computers were more than 15 years away. D-Wave’s stock price, which had been struggling, has seen a considerable bump in recent months alongside a broader boost in the quantum market. The price popped after its most recent earnings, shared right after its quantum supremacy announcement. 

The beat goes on

Some of this is standard in science. There’s always a debate over big claims and it’s not unusual for people to get over excited and have to make a retraction. Scientists are people too. That said, there’s a lot of money on the line and that appears to be making situation even more volatile than usual.

That last paragraph was completed on the morning of March 21, 2025 and later that afternoon I came across this March 21, 2025 article by Michael Grothaus for Fast Company, Note: Links have been removed,

Quantum computing stocks got pummeled yesterday, with the four most prominent public quantum computing companies—IonQ, Rigetti Computing, Quantum Computing Inc., and D-Wave Quantum Inc.—falling anywhere from over 9% to over 18%. The reason? A lot of it may have to do with AI chip giant Nvidia. Again.

Stocks crash yesterday on Nvidia quantum news

Yesterday was a bit of a bloodbath on the stock market for the four most prominent publicly traded quantum computing companies. …

All four of these quantum computing stocks [IonQ, Inc.; Rigetti Computing, Inc.; Quantum Computing Inc.; D-Wave Quantum Inc.] tumbled on the day that AI chip giant Nvidia kicked off its two-day Quantum Day event. In a blog post from January 14 announcing Quantum Day, Nvidia said the event “brings together leading experts for a comprehensive and balanced perspective on what businesses should expect from quantum computing in the coming decades — mapping the path toward useful quantum applications.”

Besides bringing quantum experts together, the AI behemoth also announced that it will be launching a new quantum computing research center in Boston.

Called the NVIDIA Accelerated Quantum Research Center (NVAQC), the new research lab “will help solve quantum computing’s most challenging problems, ranging from qubit noise to transforming experimental quantum processors into practical devices,” the company said in a press release.

The NVAQC’s location in Boston means it will be near both Harvard University and the Massachusetts Institute of Technology (MIT). 

Before Nvidia’s announcement yesterday, IonQ, Rigetti, D-Wave, and Quantum Computing Inc. were the leaders in the nascent field of quantum computing. And while they still are right now (Nvidia’s quantum research lab hasn’t been built yet), the fear is that Nvidia could use its deep pockets to quickly buy its way into a leadership spot in the field. With its $2.9 trillion market cap, the company can easily afford to throw billions of research dollars into quantum computing.

As noted by the Motley Fool, the location of the NVIDIA Accelerated Quantum Research Center in Boston will also allow Nvidia to more easily tap into top quantum talent from Harvard and MIT—talent that may have otherwise gone to IonQ, Rigetti, D-Wave, and Quantum Computing Inc.

Nvidia’s announcement is a massive about-face from the company in regard to how it views quantum computing. It’s also the second time that Nvidia has caused quantum stocks to crash this year. Back in January, shares in prominent quantum computing companies fell after Huang said that practical use of quantum computing was decades away.

Those comments were something quantum computing company CEOs like D-Wave’s Alan Baratz took issue with. “It’s an egregious error on Mr. Huang’s part,” Bartaz told Fast Company at the time. “We’re not decades away from commercial quantum computers. They exist. There are companies that are using our quantum computer today.”

According to Investor’s Business Daily, Huang reportedly got the idea for Nvidia’s Quantum Day event after the blowback to his comments, inviting quantum computing executives to the event to explain why he was incorrect about quantum computing.

The word is volatile.

One-dimensional quantum nanowires and Majorana zero modes

Length but no width or height? That’s a quantum nanowire according to a Jan. 18, 2021 news item on Nanowerk (Note: A link has been removed),

Why is studying spin properties of one-dimensional quantum nanowires important?

Quantum nanowires–which have length but no width or height–provide a unique environment for the formation and detection of a quasiparticle known as a Majorana zero mode.

A new UNSW [University of New South Wales]-led study (Nature Communications, “New signatures of the spin gap in quantum point contacts”) overcomes previous difficulty detecting the Majorana zero mode, and produces a significant improvement in device reproducibility.

Potential applications for Majorana zero modes include fault-resistant topological quantum computers, and topological superconductivity.

A Jan. 19 (?), 2021 ARC (Australian Research Council) Centre of Excellence in Future Low-Energy Electronics Technologies (or FLEET) press release (also on EurekAlert), which originated the news item, provides more detail about the research,

MAJORANA FERMIONS IN 1D WIRES

A Majorana fermion is a composite particle that is its own antiparticle.

Antimatter explainer: Every fundamental particle has a corresponding antimatter particle, with the same mass but opposite electrical charge. For example, the antiparticle of an electron (charge -1) is a positron (charge +1)

Such unusual particle’s interest academically and commercially comes from their potential use in a topological quantum computer, predicted to be immune to the decoherence that randomises the precious quantum information.

Majorana zero modes can be created in quantum wires made from special materials in which there is a strong coupling between their electrical and magnetic properties.

In particular, Majorana zero modes can be created in one-dimensional semiconductors (such as semiconductor nanowires) when coupled with a superconductor.

In a one-dimensional nanowire, whose dimensions perpendicular to length are small enough not to allow any movement of subatomic particles, quantum effects predominate.

NEW METHOD FOR DETECTING NECESSARY SPIN-ORBIT GAP

Majorana fermions, which are their own antiparticle, have been theorised since 1937, but have only been experimentally observed in the last decade. The Majorana fermion’s ‘immunity’ to decoherence provides potential use for fault-tolerant quantum computing.

One-dimensional semiconductor systems with strong spin-orbit interaction are attracting great attention due to potential applications in topological quantum computing.

The magnetic ‘spin’ of an electron is like a little bar magnet, whose orientation can be set with an applied magnetic field.

In materials with a ‘spin-orbit interaction’ the spin of an electron is determined by the direction of motion, even at zero magnetic field. This allows for all electrical manipulation of magnetic quantum properties.

Applying a magnetic field to such a system can open an energy gap such that forward -moving electrons all have the same spin polarisation, and backward-moving electrons have the opposite polarisation. This ‘spin-gap’ is a pre-requisite for the formation of Majorana zero modes.

Despite intense experimental work, it has proven extremely difficult to unambiguously detect this spin-gap in semiconductor nanowires, since the spin-gap’s characteristic signature (a dip in its conductance plateau when a magnetic field is applied) is very hard to distinguish from unavoidable the background disorder in nanowires.

The new study finds a new, unambiguous signature for the spin-orbit gap that is impervious to the disorder effects plaguing previous studies.

“This signature will become the de-facto standard for detecting spin-gaps in the future,” says lead author Dr Karina Hudson.

REPRODUCIBILITY

The use of Majorana zero modes in a scalable quantum computer faces an additional challenge due to the random disorder and imperfections in the self-assembled nanowires that host the MZM.

It has previously been almost impossible to fabricate reproducible devices, with only about 10% of devices functioning within desired parameters.

The latest UNSW results show a significant improvement, with reproducible results across six devices based on three different starting wafers.

“This work opens a new route to making completely reproducible devices,” says corresponding author Prof Alex Hamilton UNSW).

Here’s a link to and a citation for the paper,

New signatures of the spin gap in quantum point contacts by K. L. Hudson, A. Srinivasan, O. Goulko, J. Adam, Q. Wang, L. A. Yeoh, O. Klochan, I. Farrer, D. A. Ritchie, A. Ludwig, A. D. Wieck, J. von Delft & A. R. Hamilton. Nature Communications volume 12, Article number: 5 (2021) DOI: https://doi.org/10.1038/s41467-020-19895-3 Published: 04 January 2021

This paper is open access.

For anyone who might find references to UNSW and ARC/FLEET confusing, I found this in the ARC Centre of Excellence in Future Low-Energy Electronics Technologies Wikipedia entry,

The ARC Centre of Excellence in Future Low-Energy Electronics Technologies (or FLEET) is a collaboration …

FLEET is an Australian initiative, headquartered at Monash University, and in conjunction with the Australian National University, the University of New South Wales, the University of Queensland, RMIT University, the University of Wollongong and Swinburne University of Technology, complemented by a group of Australian and international partners. It is funded by the Australian Research Council [ARC] and by the member universities. [emphases as seen here are mine]

A quantum phenomenon (Kondo effect) and nanomaterials

This is a little outside my comfort zone but here goes anyway. From a December 23, 2020 news item on phys.org (Note: Links have been removed),

Osaka City University scientists have developed mathematical formulas to describe the current and fluctuations of strongly correlated electrons in quantum dots. Their theoretical predictions could soon be tested experimentally.

Theoretical physicists Yoshimichi Teratani and Akira Oguri of Osaka City University, and Rui Sakano of the University of Tokyo have developed mathematical formulas that describe a physical phenomenon happening within quantum dots and other nanosized materials. The formulas, published in the journal Physical Review Letters, could be applied to further theoretical research about the physics of quantum dots, ultra-cold atomic gasses, and quarks.

At issue is the Kondo effect. This effect was first described in 1964 by Japanese theoretical physicist Jun Kondo in some magnetic materials, but now appears to happen in many other systems, including quantum dots and other nanoscale materials.

A December 23, 2020 Osaka City University press release (also on EurekAlert), which originated the news item, provides more detail,

Normally, electrical resistance drops in metals as the temperature drops. But in metals containing magnetic impurities, this only happens down to a critical temperature, beyond which resistance rises with dropping temperatures.

Scientists were eventually able to show that, at very low temperatures near absolute zero, electron spins become entangled with the magnetic impurities, forming a cloud that screens their magnetism. The cloud’s shape changes with further temperature drops, leading to a rise in resistance. This same effect happens when other external ‘perturbations’, such as a voltage or magnetic field, are applied to the metal. 

Teratani, Sakano and Oguri wanted to develop mathematical formulas to describe the evolution of this cloud in quantum dots and other nanoscale materials, which is not an easy task. 

To describe such a complex quantum system, they started with a system at absolute zero where a well-established theoretical model, namely Fermi liquid theory, for interacting electrons is applicable. They then added a ‘correction’ that describes another aspect of the system against external perturbations. Using this technique, they wrote formulas describing electrical current and its fluctuation through quantum dots. 

Their formulas indicate electrons interact within these systems in two different ways that contribute to the Kondo effect. First, two electrons collide with each other, forming well-defined quasiparticles that propagate within the Kondo cloud. More significantly, an interaction called a three-body contribution occurs. This is when two electrons combine in the presence of a third electron, causing an energy shift of quasiparticles. 

“The formulas’ predictions could soon be investigated experimentally”, Oguri says. “Studies along the lines of this research have only just begun,” he adds. 

The formulas could also be extended to understand other quantum phenomena, such as quantum particle movement through quantum dots connected to superconductors. Quantum dots could be a key for realizing quantum information technologies, such as quantum computers and quantum communication.

Here’s a link to and a citation for the paper,

Fermi Liquid Theory for Nonlinear Transport through a Multilevel Anderson Impurity by Yoshimichi Teratani, Rui Sakano, and Akira Oguri. Phys. Rev. Lett. 125, 216801 (Issue Vol. 125, Iss. 21 — 20 November 2020) DOI: https://doi.org/10.1103/PhysRevLett.125.216801 Published Online: 17 November 2020

This paper is behind a paywall.

The Weyl fermion and new electronics

This story concerns a quasiparticle (Weyl fermion) which is a different kind of particle than the nanoparticles usually mentioned here. A March 17, 2016 news item on Nanowerk profiles research that suggests the Weyl fermion may find applications in the field of electronics,

The Weyl fermion, just discovered in the past year, moves through materials practically without resistance. Now researchers are showing how it could be put to use in electronic components.

Today electronic devices consume a lot of energy and require elaborate cooling mechanisms. One approach for the development of future energy-saving electronics is to use special particles that exist only in the interior of materials but can move there practically undisturbed. Electronic components based on these so-called Weyl fermions would consume considerably less energy than present-day chips. That’s because up to now devices have relied on the movement of electrons, which is inhibited by resistance and thus wastes energy.

Evidence for Weyl fermions was discovered only in the past year, by several research teams including scientists from the Paul Scherrer Institute (PSI). Now PSI researchers have shown — within the framework of an international collaboration with two research institutions in China and the two Swiss technical universities, ETH Zurich and EPF Lausanne — that there are materials in which only one kind of Weyl fermion exists. That could prove decisive for applications in electronic components, because it makes it possible to guide the particles’ flow in the material.

A March 17, 2016 Paul Scherrer Institute (PSI) press release by Paul Piwnicki, which originated the news item, describes the work in more detail (Note: There is some redundancy),

In the past year, researchers of the Paul Scherrer Institute PSI were among those who found experimental evidence for a particle whose existence had been predicted in the 1920s — the Weyl fermion. One of the particle’s peculiarities is that it can only exist in the interior of materials. Now the PSI researchers, together with colleagues at two Chinese research institutions as well as at ETH Zurich and EPF Lausanne, have made a subsequent discovery that opens the possibility of using the movement of Weyl fermions in future electronic devices. …

Today’s computer chips use the flow of electrons that move through the device’s conductive channels. Because, along the way, electrons are always colliding with each other or with other particles in the material, a relatively high amount of energy is needed to maintain the flow. That means not only that the device wastes a lot of energy, but also that it heats itself up enough to necessitate an elaborate cooling mechanism, which in turn requires additional space and energy.

In contrast, Weyl fermions move virtually undisturbed through the material and thus encounter practically no resistance. “You can compare it to driving on a highway where all of the cars are moving freely in the same direction,” explains Ming Shi, a senior scientist at the PSI. “The electron flow in present-day chips is more comparable to driving in congested city traffic, with cars coming from all directions and getting in each other’s way.”

Important for electronics: only one kind of particle

While in the materials examined last year there were always several kinds of Weyl fermions, all moving in different ways, the PSI researchers and their colleagues have now produced a material in which only one kind of Weyl fermion occurs. “This is important for applications in electronics, because here you must be able to precisely steer the particle flow,” explains Nan Xu, a postdoctoral researcher at the PSI.

Weyl fermions are named for the German mathematician Hermann Weyl, who predicted their existence in 1929. These particles have some striking characteristics, such as having no mass and moving at the speed of light. Weyl fermions were observed as quasiparticles in so-called Weyl semimetals. In contrast to “real” particles, quasiparticles can only exist inside materials. Weyl fermions are generated through the collective motion of electrons in suitable materials. In general, quasiparticles can be compared to waves on the surface of a body of water — without the water, the waves would not exist. At the same time, their movement is independent of the water’s motion.

The material that the researchers have now investigated is a compound of the chemical elements tantalum and phosphorus, with the chemical formula TaP. The crucial experiments were carried out with X-rays at the Swiss Light Source (SLS) of the Paul Scherrer Institute.

Studying novel materials with properties that could make them useful in future electronic devices is a central research area of the Paul Scherrer Institute. In the process, the researchers pursue a variety of approaches and use many different experimental methods.

Here’s a link to and a citation for the paper,

Observation of Weyl nodes and Fermi arcs in tantalum phosphide by N. Xu, H. M. Weng, B. Q. Lv, C. E. Matt, J. Park, F. Bisti, V. N. Strocov, D. Gawryluk, E. Pomjakushina, K. Conder, N. C. Plumb, M. Radovic, G. Autès, O. V. Yazyev, Z. Fang, X. Dai, T. Qian, J. Mesot, H. Ding & M. Shi. Nature Communications 7, Article number: 11006  doi:10.1038/ncomms11006 Published 17 March 2016

This paper is open access.

Graphene, Perimeter Institute, and condensed matter physics

In short, researchers at Canada’s Perimeter Institute are working on theoretical models involving graphene. which could lead to quantum computing. A July 3, 2014 Perimeter Institute news release by Erin Bow (also on EurekAlert) provides some insight into the connections between graphene and condensed matter physics (Note: Bow has included some good basic explanations of graphene, quasiparticles, and more for beginners),

One of the hottest materials in condensed matter research today is graphene.

Graphene had an unlikely start: it began with researchers messing around with pencil marks on paper. Pencil “lead” is actually made of graphite, which is a soft crystal lattice made of nothing but carbon atoms. When pencils deposit that graphite on paper, the lattice is laid down in thin sheets. By pulling that lattice apart into thinner sheets – originally using Scotch tape – researchers discovered that they could make flakes of crystal just one atom thick.

The name for this atom-scale chicken wire is graphene. Those folks with the Scotch tape, Andre Geim and Konstantin Novoselov, won the 2010 Nobel Prize for discovering it. “As a material, it is completely new – not only the thinnest ever but also the strongest,” wrote the Nobel committee. “As a conductor of electricity, it performs as well as copper. As a conductor of heat, it outperforms all other known materials. It is almost completely transparent, yet so dense that not even helium, the smallest gas atom, can pass through it.”

Developing a theoretical model of graphene

Graphene is not just a practical wonder – it’s also a wonderland for theorists. Confined to the two-dimensional surface of the graphene, the electrons behave strangely. All kinds of new phenomena can be seen, and new ideas can be tested. Testing new ideas in graphene is exactly what Perimeter researchers Zlatko Papić and Dmitry (Dima) Abanin set out to do.

“Dima and I started working on graphene a very long time ago,” says Papić. “We first met in 2009 at a conference in Sweden. I was a grad student and Dima was in the first year of his postdoc, I think.”

The two young scientists got to talking about what new physics they might be able to observe in the strange new material when it is exposed to a strong magnetic field.

“We decided we wanted to model the material,” says Papić. They’ve been working on their theoretical model of graphene, on and off, ever since. The two are now both at Perimeter Institute, where Papić is a postdoctoral researcher and Abanin is a faculty member. They are both cross-appointed with the Institute for Quantum Computing (IQC) at the University of Waterloo.

In January 2014, they published a paper in Physical Review Letters presenting new ideas about how to induce a strange but interesting state in graphene – one where it appears as if particles inside it have a fraction of an electron’s charge.

It’s called the fractional quantum Hall effect (FQHE), and it’s head turning. Like the speed of light or Planck’s constant, the charge of the electron is a fixed point in the disorienting quantum universe.

Every system in the universe carries whole multiples of a single electron’s charge. When the FQHE was first discovered in the 1980s, condensed matter physicists quickly worked out that the fractionally charged “particles” inside their semiconductors were actually quasiparticles – that is, emergent collective behaviours of the system that imitate particles.

Graphene is an ideal material in which to study the FQHE. “Because it’s just one atom thick, you have direct access to the surface,” says Papić. “In semiconductors, where FQHE was first observed, the gas of electrons that create this effect are buried deep inside the material. They’re hard to access and manipulate. But with graphene you can imagine manipulating these states much more easily.”

In the January paper, Abanin and Papić reported novel types of FQHE states that could arise in bilayer graphene – that is, in two sheets of graphene laid one on top of another – when it is placed in a strong perpendicular magnetic field. In an earlier work from 2012, they argued that applying an electric field across the surface of bilayer graphene could offer a unique experimental knob to induce transitions between FQHE states. Combining the two effects, they argued, would be an ideal way to look at special FQHE states and the transitions between them.

Once the scientists developed their theory they went to work on some experiments,

Two experimental groups – one in Geneva, involving Abanin, and one at Columbia, involving both Abanin and Papić – have since put the electric field + magnetic field method to good use. The paper by the Columbia group appears in the July 4 issue of Science. A third group, led by Amir Yacoby of Harvard, is doing closely related work.

“We often work hand-in-hand with experimentalists,” says Papić. “One of the reasons I like condensed matter is that often even the most sophisticated, cutting-edge theory stands a good chance of being quickly checked with experiment.”

Inside both the magnetic and electric field, the electrical resistance of the graphene demonstrates the strange behaviour characteristic of the FQHE. Instead of resistance that varies in a smooth curve with voltage, resistance jumps suddenly from one level to another, and then plateaus – a kind of staircase of resistance. Each stair step is a different state of matter, defined by the complex quantum tangle of charges, spins, and other properties inside the graphene.

“The number of states is quite rich,” says Papić. “We’re very interested in bilayer graphene because of the number of states we are detecting and because we have these mechanisms – like tuning the electric field – to study how these states are interrelated, and what happens when the material changes from one state to another.”

For the moment, researchers are particularly interested in the stair steps whose “height” is described by a fraction with an even denominator. That’s because the quasiparticles in that state are expected to have an unusual property.

There are two kinds of particles in our three-dimensional world: fermions (such as electrons), where two identical particles can’t occupy one state, and bosons (such as photons), where two identical particles actually want to occupy one state. In three dimensions, fermions are fermions and bosons are bosons, and never the twain shall meet.

But a sheet of graphene doesn’t have three dimensions – it has two. It’s effectively a tiny two-dimensional universe, and in that universe, new phenomena can occur. For one thing, fermions and bosons can meet halfway – becoming anyons, which can be anywhere in between fermions and bosons. The quasiparticles in these special stair-step states are expected to be anyons.

In particular, the researchers are hoping these quasiparticles will be non-Abelian anyons, as their theory indicates they should be. That would be exciting because non-Abelian anyons can be used in the making of qubits.

Graphene qubits?

Qubits are to quantum computers what bits are to ordinary computers: both a basic unit of information and the basic piece of equipment that stores that information. Because of their quantum complexity, qubits are more powerful than ordinary bits and their power grows exponentially as more of them are added. A quantum computer of only a hundred qubits can tackle certain problems beyond the reach of even the best non-quantum supercomputers. Or, it could, if someone could find a way to build stable qubits.

The drive to make qubits is part of the reason why graphene is a hot research area in general, and why even-denominator FQHE states – with their special anyons – are sought after in particular.

“A state with some number of these anyons can be used to represent a qubit,” says Papić. “Our theory says they should be there and the experiments seem to bear that out – certainly the even-denominator FQHE states seem to be there, at least according to the Geneva experiments.”

That’s still a step away from experimental proof that those even-denominator stair-step states actually contain non-Abelian anyons. More work remains, but Papić is optimistic: “It might be easier to prove in graphene than it would be in semiconductors. Everything is happening right at the surface.”

It’s still early, but it looks as if bilayer graphene may be the magic material that allows this kind of qubit to be built. That would be a major mark on the unlikely line between pencil lead and quantum computers.

Here are links for further research,

January PRL paper mentioned above: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.112.046602

Experimental paper from the Geneva graphene group, including Abanin: http://pubs.acs.org/doi/abs/10.1021/nl5003922

Experimental paper from the Columbia graphene group, including both Abanin and Papić: http://arxiv.org/abs/1403.2112. This paper is featured in the journal Science.

Related experiment on bilayer graphene by Amir Yacoby’s group at Harvard: http://www.sciencemag.org/content/early/2014/05/28/science.1250270

The Nobel Prize press release on graphene, mentioned above: http://www.nobelprize.org/nobel_prizes/physics/laureates/2010/press.html

I recently posted a piece about some research into the ‘scotch-tape technique’ for isolating graphene (June 30, 2014 posting). Amusingly, Geim argued against coining the technique as the ‘scotch-tape’ technique, something I found out only recently.