MSGID: 1:317/3 62735348   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    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.   
      
      
      
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   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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