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Alexander Bilmes

PhD in physics at KIT, Karlsruhe, Germany: on developing superconducting quantum detectors for tunneling two-level-systems (TLS), and on TLS research in readily-made superconducting qubits. Expert in microfabrication and design of superconducting quantum circuits, as well as in cryogenic operation and quantum manipulation of superconducting qubits.

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    Dynamics of magnetization at infinite temperature in a Heisenberg spin chain
    Trond Andersen
    Rhine Samajdar
    Andre Petukhov
    Jesse Hoke
    Dmitry Abanin
    ILYA Drozdov
    Xiao Mi
    Alexis Morvan
    Charles Neill
    Rajeev Acharya
    Richard Ross Allen
    Kyle Anderson
    Markus Ansmann
    Frank Arute
    Kunal Arya
    Juan Atalaya
    Gina Bortoli
    Alexandre Bourassa
    Leon Brill
    Michael Broughton
    Bob Buckley
    Tim Burger
    Nicholas Bushnell
    Juan Campero
    Hung-Shen Chang
    Jimmy Chen
    Benjamin Chiaro
    Desmond Chik
    Josh Cogan
    Roberto Collins
    Paul Conner
    William Courtney
    Alex Crook
    Ben Curtin
    Agustin Di Paolo
    Andrew Dunsworth
    Clint Earle
    Lara Faoro
    Edward Farhi
    Reza Fatemi
    Vinicius Ferreira
    Ebrahim Forati
    Austin Fowler
    Brooks Foxen
    Gonzalo Garcia
    Élie Genois
    William Giang
    Dar Gilboa
    Raja Gosula
    Alejo Grajales Dau
    Steve Habegger
    Michael Hamilton
    Monica Hansen
    Sean Harrington
    Paula Heu
    Gordon Hill
    Trent Huang
    Ashley Huff
    Bill Huggins
    Sergei Isakov
    Justin Iveland
    Zhang Jiang
    Cody Jones
    Pavol Juhas
    Mostafa Khezri
    Marika Kieferova
    Alexei Kitaev
    Andrey Klots
    Alexander Korotkov
    Fedor Kostritsa
    John Mark Kreikebaum
    Dave Landhuis
    Pavel Laptev
    Kim Ming Lau
    Lily Laws
    Joonho Lee
    Kenny Lee
    Yuri Lensky
    Alexander Lill
    Wayne Liu
    Salvatore Mandra
    Orion Martin
    Steven Martin
    Seneca Meeks
    Amanda Mieszala
    Shirin Montazeri
    Ramis Movassagh
    Wojtek Mruczkiewicz
    Ani Nersisyan
    Michael Newman
    JiunHow Ng
    Murray Ich Nguyen
    Tom O'Brien
    Seun Omonije
    Alex Opremcak
    Rebecca Potter
    Leonid Pryadko
    David Rhodes
    Charles Rocque
    Negar Saei
    Kannan Sankaragomathi
    Henry Schurkus
    Christopher Schuster
    Mike Shearn
    Aaron Shorter
    Noah Shutty
    Vladimir Shvarts
    Vlad Sivak
    Jindra Skruzny
    Clarke Smith
    Rolando Somma
    George Sterling
    Doug Strain
    Marco Szalay
    Doug Thor
    Alfredo Torres
    Guifre Vidal
    Benjamin Villalonga
    Cheng Xing
    Jamie Yao
    Ping Yeh
    Juhwan Yoo
    Grayson Young
    Yaxing Zhang
    Ningfeng Zhu
    Jeremy Hilton
    Anthony Megrant
    Yu Chen
    Vadim Smelyanskiy
    Vedika Khemani
    Sarang Gopalakrishnan
    Tomaž Prosen
    Science, vol. 384 (2024), pp. 48-53
    Preview abstract Understanding universal aspects of quantum dynamics is an unresolved problem in statistical mechanics. In particular, the spin dynamics of the one-dimensional Heisenberg model were conjectured as to belong to the Kardar-Parisi-Zhang (KPZ) universality class based on the scaling of the infinite-temperature spin-spin correlation function. In a chain of 46 superconducting qubits, we studied the probability distribution of the magnetization transferred across the chain’s center, P(M). The first two moments of P(M) show superdiffusive behavior, a hallmark of KPZ universality. However, the third and fourth moments ruled out the KPZ conjecture and allow for evaluating other theories. Our results highlight the importance of studying higher moments in determining dynamic universality classes and provide insights into universal behavior in quantum systems. View details
    Resolving catastrophic error bursts from cosmic rays in large arrays of superconducting qubits
    Lara Faoro
    Kunal Arya
    Andrew Dunsworth
    Trent Huang
    Austin Fowler
    Frank Arute
    Bob B. Buckley
    Nicholas Bushnell
    Jimmy Chen
    Roberto Collins
    Alan R. Derk
    Sean Harrington
    Fedor Kostritsa
    Pavel Laptev
    Xiao Mi
    Shirin Montazeri
    Josh Mutus
    Charles Neill
    Alex Opremcak
    Nicholas Redd
    Vladimir Shvarts
    Jamie Yao
    Ping Yeh
    Juhwan Yoo
    Yu Chen
    Vadim Smelyanskiy
    John Martinis
    Anthony Megrant
    Rami Barends
    Nature Physics (2021)
    Preview abstract Scalable quantum computing can become a reality with error correction, provided that coherent qubits can be constructed in large arrays. The key premise is that physical errors can remain both small and sufficiently uncorrelated as devices scale, so that logical error rates can be exponentially suppressed. However, impacts from cosmic rays and latent radioactivity violate these assumptions. An impinging particle can ionize the substrate and induce a burst of quasiparticles that destroys qubit coherence throughout the device. High-energy radiation has been identified as a source of error in pilot superconducting quantum devices, but the effect on large-scale algorithms and error correction remains an open question. Elucidating the physics involved requires operating large numbers of qubits at the same rapid timescales necessary for error correction. Here, we use space- and time-resolved measurements of a large-scale quantum processor to identify bursts of quasiparticles produced by high-energy rays. We track the events from their initial localized impact as they spread, simultaneously and severely limiting the energy coherence of all qubits and causing chip-wide failure. Our results provide direct insights into the impact of these damaging error bursts and highlight the necessity of mitigation to enable quantum computing to scale. View details
    Realizing topologically ordered states on a quantum processor
    Y.-J. Liu
    A. Smith
    C. Knapp
    M. Newman
    N. C. Jones
    Z. Chen
    X. Mi
    A. Dunsworth
    I. Aleiner
    F. Arute
    K. Arya
    J. Atalaya
    R. Barends
    J. Basso
    M. Broughton
    B. B. Buckley
    N. Bushnell
    B. Chiaro
    R. Collins
    W. Courtney
    A. R Derk
    D. Eppens
    L. Faoro
    E. Farhi
    B. Foxen
    A. Greene
    S. D. Harrington
    J. Hilton
    T. Huang
    W. J. Huggins
    S. V. Isakov
    Z. Jiang
    K. Kechedzhi
    A. N. Korotkov
    F. Kostritsa
    D. Landhuis
    P. Laptev
    O. Martin
    M. Mohseni
    S. Montazeri
    W. Mruczkiewicz
    J. Mutus
    C. Neill
    T. E. O'Brien
    A. Opremcak
    B. Pato
    A. Petukhov
    V. Shvarts
    D. Strain
    M. Szalay
    B. Villalonga
    Z. Yao
    P. Yeh
    J. Yoo
    A. Megrant
    Y. Chen
    V. Smelyanskiy
    A. Kitaev
    M. Knap
    F. Pollmann
    Science, vol. 374 (2021), pp. 1237-1241
    Preview abstract The discovery of topological order has revolutionized the understanding of quantum matter in modern physics and provided the theoretical foundation for many quantum error correcting codes. Realizing topologically ordered states has proven to be extremely challenging in both condensed matter and synthetic quantum systems. Here, we prepare the ground state of the emblematic toric code Hamiltonian using an efficient quantum circuit on a superconducting quantum processor. We measure a topological entanglement entropy of Stopo ≈ −0.95 × ln 2 and simulate anyon interferometry to extract the braiding statistics of the emergent excitations. Furthermore, we investigate key aspects of the surface code, including logical state injection and the decay of the non-local order parameter. Our results illustrate the topological nature of these states and demonstrate their potential for implementing the surface code. View details
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