• The quest for an ideal quantum bit

    From ScienceDaily@1:317/3 to All on Wednesday, May 04, 2022 22:30:50
    The quest for an ideal quantum bit

    Date:
    May 4, 2022
    Source:
    DOE/Argonne National Laboratory
    Summary:
    Scientists have developed a qubit platform formed by freezing neon
    gas into a solid, spraying electrons from a light bulb's filament
    onto it, and trapping a single electron there. This system shows
    great promise as an ideal building block for quantum computers.



    FULL STORY ==========================================================================
    New qubit platform could transform quantum information science and
    technology.


    ==========================================================================
    You are no doubt viewing this article on a digital device whose basic unit
    of information is the bit, either 0 or 1. Scientists worldwide are racing
    to develop a new kind of computer based on use of quantum bits, or qubits.

    In a recent Nature paper, a team led by the U.S. Department of Energy's
    (DOE) Argonne National Laboratory has announced the creation of a new
    qubit platform formed by freezing neon gas into a solid at very low temperatures, spraying electrons from a light bulb's filament onto the
    solid, and trapping a single electron there. This system shows great
    promise to be developed into ideal building blocks for future quantum computers.

    To realize a useful quantum computer, the quality requirements for the
    qubits are extremely demanding. While there are various forms of qubits
    today, none of them is ideal.

    What would make an ideal qubit? It has at least three sterling qualities, according to Dafei Jin, an Argonne scientist and the principal
    investigator of the project.

    It can remain in a simultaneous 0 and 1 state (remember the cat!) over
    a long time. Scientists call this long "coherence." Ideally, that time
    would be around a second, a time step that we can perceive on a home
    clock in our daily life.



    ========================================================================== Second, the qubit can be changed from one state to another in a short
    time.

    Ideally, that time would be around a billionth of a second (nanosecond),
    a time step of a classical computer clock.

    Third, the qubit can be easily linked with many other qubits so they
    can work in parallel with each other. Scientists refer to this linking
    as entanglement.

    Although at present the well-known qubits are not ideal, companies
    like IBM, Intel, Google, Honeywell and many startups have picked their favorite. They are aggressively pursuing technological improvement and commercialization.

    "Our ambitious goal is not to compete with those companies, but to
    discover and construct a fundamentally new qubit system that could lead
    to an ideal platform," said Jin.

    While there are many choices of qubit types, the team chose the simplest
    one - - a single electron. Heating up a simple light filament you
    might find in a child's toy can easily shoot out a boundless supply
    of electrons.



    ==========================================================================
    One of the challenges for any qubit, including the electron, is that it
    is very sensitive to disturbance from its surroundings. Thus, the team
    chose to trap an electron on an ultrapure solid neon surface in a vacuum.

    Neon is one of a handful of inert elements that do not react with other elements. "Because of this inertness, solid neon can serve as the cleanest possible solid in a vacuum to host and protect any qubits from being disrupted," said Jin.

    A key component in the team's qubit platform is a chip-scale microwave resonator made out of a superconductor. (The much larger home microwave
    oven is also a microwave resonator.) Superconductors -- metals with no electrical resistance -- allow electrons and photons to interact together
    at near to absolute zero with minimal loss of energy or information.

    "The microwave resonator crucially provides a way to read out the state
    of the qubit," said Kater Murch, physics professor at the Washington
    University in St.

    Louis and a senior co-author of the paper. "It concentrates the
    interaction between the qubit and microwave signal. This allows us to make measurements telling how well the qubit works." "With this platform,
    we achieved, for the first time ever, strong coupling between a single
    electron in a near-vacuum environment and a single microwave photon in
    the resonator," said Xianjing Zhou, a postdoctoral appointee at Argonne
    and the first author of the paper. ?"This opens up the possibility to
    use microwave photons to control each electron qubit and link many of
    them in a quantum processor," Zhou added.

    The team tested the platform in a scientific instrument called a
    dilution refrigerator, which can reach temperatures as low as a mere 10 millidegrees above absolute zero. This instrument is one of many quantum capabilities in Argonne's Center for Nanoscale Materials, a DOE Office
    of Science user facility.

    The team performed real-time operations to an electron qubit and
    characterized its quantum properties. These tests demonstrated that the
    solid neon provides a robust environment for the electron with very low electric noise to disturb it.

    Most importantly, the qubit attained coherence times in the quantum
    state competitive with state-of-the-art qubits.

    "Our qubits are actually as good as ones that people have been developing
    for 20 years," said David Schuster, physics professor at the University
    of Chicago and a senior co-author of the paper. "This is only our first
    series of experiments. Our qubit platform is nowhere near optimized. We
    will continue improving the coherence times. And because the operation
    speed of this qubit platform is extremely fast, only several nanoseconds,
    the promise to scale it up to many entangled qubits is significant."
    There is yet one more advantage to this remarkable qubit platform. "Thanks
    to the relative simplicity of the electron-on-neon platform, it should
    lend itself to easy manufacture at low cost," Jin said. "It would
    appear an ideal qubit may be on the horizon." The team published their findings in a Nature article titled "Single electrons on solid neon
    as a solid-state qubit platform." In addition to Jin and Zhou, Argonne contributors include Xufeng Zhang, Xu Han, Xinhao Li and Ralu Divan. In addition to David Schuster, the University of Chicago contributors
    also include Brennan Dizdar. In addition to Kater Murch of Washington University in St.

    Louis, other researchers include Wei Guo of Florida State University,
    Gerwin Koolstra of Lawrence Berkeley National Laboratory and Ge Yang of Massachusetts Institute of Technology.

    Funding for the Argonne research primarily came from the DOE Office
    of Basic Energy Sciences, Argonne's Laboratory Directed Research and Development program and the Julian Schwinger Foundation for Physics
    Research.


    ========================================================================== Story Source: Materials provided by
    DOE/Argonne_National_Laboratory. Original written by Joseph
    E. Harmon. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Xianjing Zhou, Gerwin Koolstra, Xufeng Zhang, Ge Yang, Xu Han,
    Brennan
    Dizdar, Xinhao Li, Ralu Divan, Wei Guo, Kater W. Murch, David I.

    Schuster, Dafei Jin. Single electrons on solid neon as a
    solid-state qubit platform. Nature, 2022; 605 (7908): 46 DOI:
    10.1038/s41586-022- 04539-x ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/05/220504130823.htm

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