Vincenzo Lordi |18-ERD-039
Quantum computers offer the potential for exponentially speeding up of certain types of computations. A promising scalable approach to implement the basic units of a quantum computer, so-called quantum bits, or qubits, is to use superconducting circuits. However, higher-fidelity models of how superconducting circuits respond in the quantum regime are necessary to enable predictive design of devices, and microscopic sources of noise related to materials used in qubit fabrication strongly affect their performance and must be taken into account.
For this project we developed a new, detailed, and computationally efficient modeling framework to simulate the response of superconducting circuit-based quantum devices. Specifically, we developed and exercised a new multiscale modeling capability that predicts the most important properties of a Josephson junction, a critical component of any superconducting qubit. The capability is based on atomistic models at the first-principles level, but it predicts and connects to macroscopic properties of the device, such as critical current and tunneling transparency, allowing for computational design and evaluation of novel junction materials and processes. We also analyzed how correlated spin dynamics associated with adsorbed molecules on the surface of a device can influence magnetic flux noise as a potential limiting noise source. The integrated modeling capability is a major step toward bottom-up high-fidelity rational design of superconducting circuit-based quantum information devices. This project also led to new understanding of key materials properties that cause some of the underlying noise in these devices, providing insight that can benefit follow-on studies regarding materials and process optimization for breakthrough higher-performance qubits.
We generated capabilities and knowledge that will enable Lawrence Livermore National Laboratory to have impact in missions associated with quantum sensors and computing devices by enabling higher-fidelity designs, interpretation of experiments, and optimization of experiments and devices. These capabilities position the Laboratory for impactful follow-on work relevant to the Laboratory, the Department of Energy, and other national missions. This project is aligned with the Laboratory's quantum science and technology mission research challenge and crosscuts Livermore's core competencies in advanced materials and manufacturing and high-performance computing, simulation, and data science. The project contributes enabling capabilities to support long-term needs in quantum-coherent superconducting device design for sensors, simulation, and information processing. The tools and knowledge generated provide capabilities in integrated simulation of materials and quantum device. Advances in highly-correlated physics at the mesoscale, specifically the understanding of the behavior of ensembles of paramagnetic impurities on device surfaces, will impact the materials science mission. These advancements provide early results and capabilities to enable follow-on funding in research fields of highly-correlated materials and quantum information science. Long-term, we expect this work to further contribute enabling technology for the development and fabrication of next-generation quantum computing platforms, which may broadly impact Livermore's high-performance computing, simulation, and data science core competency.
Publications, Presentations, and Patents
Kim, C.-E., et al. 2018. "Electronic structure and surface properties of MgB2(0001) upon oxygen adsorption." Physical Review B 97:195416. LLNL-JRNL-73684
——— 2019a. "A density-functional theory study on Al/AlOx/Al tunneling junction." Materials Research Society Spring Meeting, Phoenix, AZ, April 2019. LLNL-PRES-772888
——— 2019b. "A density-functional theory study on Al/AlOx/Al tunneling junction." Workshop on Recent Developments in Electronic Structure, Urbana, IL, May 2019. LLNL-POST-774345
——— 2019c. "Lattice-Matching Strategy for Coherent Interface Design of Josephson Junction—Al/AlOx/Al vs Re/Al2O3/Re." Materials Research Society Fall Meeting, Boston, MA, December 2019. LLNL-ABS-777997
——— 2020a."Density-functional theory study of the Al/AlOx/Al tunnel junction." Journal of Applied Physics 128:155102. LLNL-JRNL-777557
——— 2020b. "Ab-initio Calculation of Quantum Tunneling Property of Thin Oxide Josephson Junctions Using Density Functional Theory and Machine-Learning." IEEE Semiconductor Interface Specialists Conference (online), December 2020. LLNL-ABS-814477
Lordi, V. 2017. "Tutorial for EM8 Symposium: Materials for Quantum Information PART 3." Materials Research Society Fall Meeting, Boston, MA, November 2017. LLNL-PRES-741274
——— 2018. "Quantum Langevin Dynamics of a Multiport, Multimode Superconducting Circuit." American Physical Society March Meeting, Los Angeles, CA, March 2018. LLNL-ABS-740817
——— 2019a. "First Principles Atomistic Modeling of Decoherence Sources in Qubit Devices." Materials Research Society Spring Meeting, Phoenix, AZ, April 2019. LLNL-PRES-772927
——— 2019b. "Microscopic Sources of Noise and Decoherence." MRS/Kavli Future of Materials Workshop on Solid-State Materials and Quantum Information, Phoenix, AZ, April 2019. LLNL-PRES-773460
——— 2019c. "Predictive Atomistic Modeling of Decoherence Sources in Superconducting, Semiconducting, and Surface Ion Trap Qubit Devices." IBM Almaden Colloquium, San Jose, CA, May 2019. LLNL-ABS-772598
Ray, K. G., et al. 2017. "Ab Initio Investigation of Interacting Surface Spin Dynamics as a Flux Noise Origin in Superconducting Qubits." Materials Research Society Fall Meeting, Boston, MA, November/December 2017. LLNL-PRES-742461
——— 2018a. "Emergent Dynamics of Noise and Loss-Generating Paramagnetic Spins in Superconducting Circuits." American Physical Society March Meeting, Los Angeles, CA, March 2018. LLNL-PRES-747562
——— 2018b. "Superconducting Qubit Decoherence due to Paramagnetic Surface Adsorbate Spin Dynamics." Materials Research Society Spring Meeting, Phoenix, AZ, April 2018. LLNL-ABS-744904
——— 2018c. "Theoretical Studies on the Materials Origins of Decoherence in Quantum Information Systems." Molecular Foundry User Meeting, Berkeley, CA, August 2018. LLNL-PRES-756674
——— 2019. "Magneto-Electric Coupling of Noise and Loss-Generating Paramagnetic Spins in Superconducting Circuits." American Physical Society March Meeting, Boston, MA, March 2019. LLNL-PRES-769099
Richardson, C. J. K., et al. 2020. "Materials Science for Quantum Information Science and Technology." MRS Bulletin 45(6):485-497. LLNL-JRNL-807063
Rosen, Y. J. 2019. "Probing two level systems at the material interfaces of superconducting devices." Workshop on Atomic Tunneling Systems and Fluctuating Spins Interacting with Superconducting Qubits (TLSQU19), Dresden, Germany, February/March 2019. LLNL-PRES-768212