Scientists performed transmission electron microscopy and x-ray photoelectron spectroscopy (XPS) at Brookhaven Labs Center for Functional Nanomaterials and National Synchrotron Light Source II to characterize the properties of niobium thin films made into superconducting qubit devices at Princeton University. A transmission electron microscope image of one of these films is shown in the background; overlaid on this image are XPS spectra (colored lines representing the relative concentrations of niobium metal and various niobium oxides as a function of film depth) and an illustration of a qubit device. Through these and other microscopy and spectroscopy studies, the team identified atomic-scale structural and surface chemistry defects that may be causing loss of quantum informationa hurdle to enabling practical quantum computers. Credit: Brookhaven National Laboratory
Brookhaven Lab and Princeton scientists team up to identify sources of loss of quantum information at the atomic scale.
Engineers and materials scientists studying superconducting quantum information bits (qubits)a leading quantum computing material platform based on the frictionless flow of paired electronshave collected clues hinting at the microscopic sources of qubit information loss. This loss is one of the major obstacles in realizing quantum computers capable of stringing together millions of qubits to run demanding computations. Such large-scale, fault-tolerant systems could simulate complicated molecules for drug development, accelerate the discovery of new materials for clean energy, and perform other tasks that would be impossible or take an impractical amount of time (millions of years) for todays most powerful supercomputers.
An understanding of the nature of atomic-scale defects that contribute to qubit information loss is still largely lacking. The team helped bridge this gap between material properties and qubit performance by using state-of-the-art characterization capabilities at the Center for Functional Nanomaterials (CFN) and National Synchrotron Light Source II (NSLS-II), both U.S. Department of Energy (DOE) Office of Science User Facilities at Brookhaven National Laboratory. Their results pinpointed structural and surface chemistry defects in superconducting niobium qubits that may be causing loss.
Superconducting qubits are a promising quantum computing platform because we can engineer their properties and make them using the same tools used to make regular computers, said Anjali Premkumar, a fourth-year graduate student in the Houck Lab at Princeton University and first author on the Communications Materials paper describing the research. However, they have shorter coherence times than other platforms.
In other words, they cant hold onto information very long before they lose it. Though coherence times have recently improved from microseconds to milliseconds for single qubits, these times significantly decrease when multiple qubits are strung together.
Qubit coherence is limited by the quality of the superconductors and the oxides that will inevitably grow on them as the metal comes into contact with oxygen in the air, continued Premkumar. But, as qubit engineers, we havent characterized our materials in great depth. Here, for the first time, we collaborated with materials experts who can carefully look at the structure and chemistry of our materials with sophisticated tools.
This collaboration was a prequel to the Co-design Center for Quantum Advantage (C2QA), one of five National Quantum Information Science Centers established in 2020 in support of the National Quantum Initiative. Led by Brookhaven Lab, C2QA brings together hardware and software engineers, physicists, materials scientists, theorists, and other experts across national labs, universities, and industry to resolve performance issues with quantum hardware and software. Through materials, devices, and software co-design efforts, the C2QA team seeks to understand and ultimately control material properties to extend coherence times, design devices to generate more robust qubits, optimize algorithms to target specific scientific applications, and develop error-correction solutions.
In this study, the team fabricated thin films of niobium metal through three different sputtering techniques. In sputtering, energetic particles are fired at a target containing the desired material; atoms are ejected from the target material and land on a nearby substrate. Members of the Houck Lab performed standard (direct current) sputtering, while Angstrom Engineering applied a new form of sputtering they specialize in (high-power impulse magnetron sputtering, or HiPIMS), where the target is struck with short bursts of high-voltage energy. Angstrom carried out two variations of HiPIMS: normal and with an optimized power and target-substrate geometry.
Back at Princeton, Premkumar made transmon qubit devices from the three sputtered films and placed them in a dilution refrigerator. Inside this refrigerator, temperatures can plunge to near absolute zero (minus 459.67 degrees Fahrenheit), turning qubits superconducting. In these devices, superconducting pairs of electrons tunnel across an insulating barrier of aluminum oxide (Josephson junction) sandwiched between superconducting aluminum layers, which are coupled to capacitor pads of niobium on sapphire. The qubit state changes as the electron pairs go from one side of the barrier to the other. Transmon qubits, co-invented by Houck Lab principal investigator and C2QA Director Andrew Houck, are a leading kind of superconducting qubit because they are highly insensitive to fluctuations in electric and magnetic fields in the surrounding environment; such fluctuations can cause qubit information loss.
For each of the three device types, Premkumar measured the energy relaxation time, a quantity related to the robustness of the qubit state.
The energy relaxation time corresponds to how long the qubit stays in the first excited state and encodes information before it decays to the ground state and loses its information, explained Ignace Jarrige, formerly a physicist at NSLS-II and now a quantum research scientist at Amazon, who led the Brookhaven team for this study.
Each device had different relaxation times. To understand these differences, the team performed microscopy and spectroscopy at the CFN and NSLS-II.
NSLS-II beamline scientists determined the oxidation states of niobium through x-ray photoemission spectroscopy with soft x-rays at the In situ and Operando Soft X-ray Spectroscopy (IOS) beamline and hard x-rays at the Spectroscopy Soft and Tender (SST-2) beamline. Through these spectroscopy studies, they identified various suboxides located between the metal and the surface oxide layer and containing a smaller amount of oxygen relative to niobium.
We needed the high energy resolution at NSLS-II to distinguish the five different oxidation states of niobium and both hard and soft x-rays, which have different energy levels, to profile these states as a function of depth, explained Jarrige. Photoelectrons generated by soft x-rays only escape from the first few nanometers of the surface, while those generated by hard x-rays can escape from deeper in the films.
At the NSLS-II Soft Inelastic X-ray Scattering (SIX) beamline, the team identified spots with missing oxygen atoms through resonant inelastic x-ray scattering (RIXS). Such oxygen vacancies are defects, which can absorb energy from qubits.
At the CFN, the team visualized film morphology using transmission electron microscopy and atomic force microscopy, and characterized the local chemical makeup near the film surface through electron energy-loss spectroscopy.
The microscope images showed grainspieces of individual crystals with atoms arranged in the same orientationsized larger or smaller depending on the sputtering technique, explained coauthor Sooyeon Hwang, a staff scientist in the CFN Electron Microscopy Group. The smaller the grains, the more grain boundaries, or interfaces where different crystal orientations meet. According to the electron energy-loss spectra, one film had not just oxides on the surface but also in the film itself, with oxygen diffused into the grain boundaries.
Their experimental findings at the CFN and NSLS-II revealed correlations between qubit relaxation times and the number and width of grain boundaries and concentration of suboxides near the surface.
Grain boundaries are defects that can dissipate energy, so having too many of them can affect electron transport and thus the ability of qubits to perform computations, said Premkumar. Oxide quality is another potentially important parameter. Suboxides are bad because electrons are not happily paired together.
Going forward, the team will continue their partnership to understand qubit coherence through C2QA. One research direction is to explore whether relaxation times can be improved by optimizing fabrication processes to generate films with larger grain sizes (i.e., minimal grain boundaries) and a single oxidation state. They will also explore other superconductors, including tantalum, whose surface oxides are known to be more chemically uniform.
From this study, we now have a blueprint for how scientists who make qubits and scientists who characterize them can collaborate to understand the microscopic mechanisms limiting qubit performance, said Premkumar. We hope other groups will leverage our collaborative approach to drive the field of superconducting qubits forward.
Reference: Microscopic relaxation channels in materials for superconducting qubits by Anjali Premkumar, Conan Weiland, Sooyeon Hwang, Berthold Jck, Alexander P. M. Place, Iradwikanari Waluyo, Adrian Hunt, Valentina Bisogni, Jonathan Pelliciari, Andi Barbour, Mike S. Miller, Paola Russo, Fernando Camino, Kim Kisslinger, Xiao Tong, Mark S. Hybertsen, Andrew A. Houck and Ignace Jarrige, 1 July 2021, Communications Materials.DOI: 10.1038/s43246-021-00174-7
This work was supported by the DOE Office of Science, National Science Foundation Graduate Research Fellowship, Humboldt Foundation, National Defense Science and Engineering Graduate Fellowship, Materials Research Science and Engineering Center, and Army Research Office. This research used resources of the Electron Microscopy, Proximal Probes, and Theory and Computation Facilities at the CFN, a DOE Nanoscale Science Research Center. The SST-2 beamline at NSLS-II is operated by the National Institute of Standards and Technology.
- Microsoft and KPMG will try out quantum algorithms on real-world problems - GeekWire - December 3rd, 2021
- Finnish Researchers Say Their First Quantum Computer Is Up and Running - Bloomberg - December 3rd, 2021
- Honeywell Superpositions Itself in the Quantum Computing Industry With New Company Quantinuum - TECHdotMN - December 3rd, 2021
- Where does EU stand in the quantum computing race with China and US? - TechHQ - December 3rd, 2021
- Pistoia Alliance predicts a focus on the fight against antimicrobial resistance and a surge in quantum computing research for 2022 - Bio-IT World - November 25th, 2021
- Atom Computing: A Quantum Computing Startup That Believes It Can Ultimately Win The Qubit Race - Forbes - November 22nd, 2021
- Creating Dynamic Symmetry in Diamond Crystals To Improve Qubits for Quantum Computing - SciTechDaily - November 22nd, 2021
- Don Kahle: Quantum quandaries are emerging - The Register-Guard - November 22nd, 2021
- 4 key threats to the new central bank digital currencies - World Economic Forum - November 22nd, 2021
- IBM creates largest ever superconducting quantum computer - New Scientist - November 15th, 2021
- Quantum computing breakthrough may help us learn about the earliest moments of the universe - TechRadar - November 15th, 2021
- Atos and NVIDIA to Advance Climate and Healthcare Research With Exascale Computing - HPCwire - November 15th, 2021
- IBM Launches Its First Quantum Computing Certification | The Info-Tech Brief - Oakland News Now - November 15th, 2021
- Intel Marks 50th Anniversary of the Intel 4004 - HPCwire - November 15th, 2021
- QCI Qatalyst Selected by BMW Group and Amazon Web Services as a Finalist in the Quantum Computing Challenge - HPCwire - November 11th, 2021
- Will Quantum Computers Burst The Bitcoin Boom? - Forbes - November 10th, 2021
- Quantum Computing Market Research Report by Technology, by Deployment, by Offering, by End-Use, by Application, by Region - Global Forecast to 2026 -... - November 10th, 2021
- Quantum Computing Inc. to Present at the ROTH 10th Annual - GlobeNewswire - November 10th, 2021
- QCI Qatalyst Selected by BMW Group and Amazon Web Services - GlobeNewswire - November 10th, 2021
- Nvidia Declares That It Is A Full-Stack Platform - The Next Platform - November 10th, 2021
- ANET: Add These 3 Soaring Computer Hardware Stocks to Your Watchlist - StockNews.com - November 10th, 2021
- Rigetti and Oxford Instruments Participate and Sponsor The City - Marketscreener.com - November 10th, 2021
- Lost in Space-Time newsletter: Will a twisted universe save cosmology? - New Scientist - November 10th, 2021
- IonQ Is First Quantum Startup to Go Public; Will It be First to Deliver Profits? - HPCwire - November 6th, 2021
- QUANTUM COMPUTING INC. Management's Discussion and Analysis of Financial Condition and Results of Operations, (form 10-Q) - marketscreener.com - November 6th, 2021
- Pasqal named startup of the year by L'Usine Nouvelle - EurekAlert - November 6th, 2021
- Quantum Blockchain Technologies Plc - Update on FPGA and ASIC Development - Yahoo Finance UK - November 6th, 2021
- Quantum Xchange Joins the Hudson Institute's Quantum Alliance Initiative - PRNewswire - November 6th, 2021
- Is This the Right Time for a Cryptography Risk Assessment? - Security Boulevard - November 6th, 2021
- IBM and Raytheon Collaborating on AI, Cryptography, and Quantum Computing - Datamation - October 30th, 2021
- AWS Announces Opening of the AWS Center for Quantum Computing - HPCwire - October 30th, 2021
- China makes a quantum computer streets ahead of the US - Fudzilla - October 30th, 2021
- CyberHive's Gareth Lockwood on how quantum computing changes the rules of threat protection - TechCentral.ie - October 30th, 2021
- Amazon partners with UCLA on science hub focusing on AI and its social impact - Yahoo Finance - October 30th, 2021
- Sumitomo Corporation Quantum Transformation (QX) Project - Quantum Computer Improves Performance of Traffic Control for Flying Cars, One Step Closer... - October 20th, 2021
- 3 CQE members Receive Awards from the American Physical Society - HPCwire - October 20th, 2021
- INSIDE QUANTUM TECHNOLOGY New York, The Largest Business Quantum Technology Conference and Exhibition, Announces Focus on Quantum Safe Initiatives and... - October 20th, 2021
- Incredible Growth of Quantum Computing in Health Care Market by 2028 | D-Wave Solutions, IBM, Google EcoChunk - EcoChunk - October 20th, 2021
- IonQ and University of Maryland Researchers Demonstrate Fault-Tolerant Error Correction, Critical for Unlocking the Full Potential of Quantum... - October 12th, 2021
- Quantum computing startups pull in millions as VCs rush to get ahead of the game - The Register - October 12th, 2021
- Zapata, University of Hull researchers take quantum computing to deep space - FierceElectronics - October 12th, 2021
- IBM and Raytheon Technologies collaborate on AI, cryptography and quantum technologies - Scientific Computing World - October 12th, 2021
- How science and diplomacy inform each other - SWI swissinfo.ch - swissinfo.ch - October 12th, 2021
- Digital Wealth Management Fees to Increase Threefold to $12.6 Billion By 2026 - Yahoo Finance - October 12th, 2021
- Is Neuromorphic Computing The Answer For Autonomous Driving And Personal Robotics? - Forbes - October 12th, 2021
- IonQ is set to make its public trading debut. Here's a look at the quantum computing company's 2021 highlights - Technical.ly DC - October 2nd, 2021
- Quantum Computing in Agriculture Market to Witness Stellar CAGR During the Forecast Period 2021 -2026 - Northwest Diamond Notes - October 2nd, 2021
- What is quantum computing? - September 21st, 2021
- Why quantum computing is a security threat and how to defend against it [Q&A] - BetaNews - September 21st, 2021
- 'This Is The Beginning Of A New Industry': College Park Looks To Quantum Computing To Spark Office Growth - Bisnow - September 21st, 2021
- Prepare for the next phase of digital transformation at The Quantum Computing Summit - UKTN - UKTN (UK Technology News - September 21st, 2021
- A Simple Equation Indicates Wormholes May Be the Key to Quantum Gravity - Interesting Engineering - September 21st, 2021
- Explore Trends and COVID-19 Impact on Quantum Computing Market 2021 Research Report and Industry Forecast till 2027 | Know More Stillwater Current -... - September 21st, 2021
- Australias nuclear submarines and AUKUS: The view from Jakarta - Brookings Institution - September 21st, 2021
- Research on Quantum Computing in Health Care Market 2021: By Growing Rate, Type, Applications, Geographical Regions, and Forecast to 2026 - Northwest... - September 15th, 2021
- Atomically-Thin, Twisted Graphene Has Unique Properties That Could Advance Quantum Computing - SciTechDaily - September 15th, 2021
- For The First Time, Scientists Have Entangled Three Qubits on Silicon - ScienceAlert - September 15th, 2021
- UChicago, Duality Teams to Pitch at 2021 Chicago Venture Summit - Polsky Center for Entrepreneurship and Innovation - Polsky Center for... - September 15th, 2021
- View: Its the Spacetime to Quantum - Economic Times - September 15th, 2021
- IonQ Scores Quantum Computing Deal With University Of Maryland And Announces Its Tripling 2021 Bookings - Forbes - September 11th, 2021
- How Horizon Plans To Bring Quantum Computing Out Of The Shadows - Forbes - September 11th, 2021
- Quantum Computing Breakthrough: Entanglement of Three Spin Qubits Achieved in Silicon - SciTechDaily - September 11th, 2021
- Quantum Computing Theorist Vojtech Vlcek Receives Research Award from DOE - HPCwire - September 11th, 2021
- UMD, IonQ join forces to create the nation's first quantum computing lab in College Park - The Diamondback - September 11th, 2021
- Quantum computing breakthrough achieved, road to the future begins now - TweakTown - September 11th, 2021
- Leading Chinese researchers are looking at the coming quantum revolution - The Press Stories - September 4th, 2021
- Top 10 Data Center Stories of the Month: August 2021 - Data Center Knowledge - September 4th, 2021
- Large-Scale Simulations Of The Brain May Need To Wait For Quantum Computers - Forbes - September 3rd, 2021
- NSA: We 'don't know when or even if' a quantum computer will ever be able to break today's public-key encryption - The Register - September 3rd, 2021
- IBM quantum computing: From healthcare to automotive to energy, real use cases are in play - TechRepublic - September 1st, 2021
- Quantum Computing in Manufacturing Market Rising Trends-Microsoft, D-Wave Solutions, Rigetti Computing, Intel UNLV The Rebel Yell - UNLV The Rebel... - September 1st, 2021
- Quantum computers could read all your encrypted data. This 'quantum-safe' VPN aims to stop that - ZDNet - August 30th, 2021
- Sumitomo Corporation Quantum Transformation (QX) Project Announces Its Vision and Activities at the IEEE Quantum AI Sustainability Symposium -... - August 30th, 2021
- Life, the universe and everything Physics seeks the future - The Economist - August 30th, 2021
- This Exotic Particle Had an Out-of-Body Experience These Surprised Scientists Took a Picture of It - SciTechDaily - August 30th, 2021
- Deloitte's quantum computing leader on the technology's healthcare future - Healthcare IT News - August 24th, 2021
- Experiments Prove Quantum Computing Errors Correlated, Tied to Cosmic Rays - SciTechDaily - August 24th, 2021
- Urgent Warning Issued Over The Future Of Bitcoin Even As The Crypto Market Price Smashes Past $2 Trillion - Forbes - August 24th, 2021
- Sumitomo Corporation Quantum Transformation (QX) Project Announces Its Vision and Activities at the IEEE Quantum AI Sustainability Symposium - Yahoo... - August 24th, 2021
- Energy Department Sets $61M of Funding to Advance QIS Research - MeriTalk - August 24th, 2021