• UCSBgauchos twitter avatar
    What a way to start off the season! @UCSBMensSoccer tops No.5 Stanford 1-0 Friday. RECAP >>> http://t.co/gPhjHwqFP0 http://t.co/z7Z90RLG5D
    8 hours 5 sec ago
  • UCSBgauchos twitter avatar
    The Gauchos start the 2015 season off in style, hold No. 8 Stanford scoreless to win 1-0. @UCSBMensSoccer first win over Stanford since 2004
    9 hours 9 min ago
  • UCSBgauchos twitter avatar
    Stanford trying desperately to get on the board but UCSB's backline can't be beat. Gauchos lead 1-0 with 5 minutes to go
    9 hours 16 min ago
  • UCSBgauchos twitter avatar
    Ahinga Selemani beats his defender to set up Geoffrey Acheampong beautifully in the box, but the lefty's shot goes wide of the post
    9 hours 43 min ago
  • UCSBgauchos twitter avatar
    Stanford with a pair of good chances with just under 30 minutes to go but UCSB still finds a way to keep them off the board and lead 1-0
    9 hours 48 min ago
  • UCSBgauchos twitter avatar
    .@UCSBMensSoccer leading No. 8 Stanford 1-0 at the half thanks to a goal by who else, Nick DePuy. Great first half for the Gauchos
    10 hours 16 min ago
  • UCSBgauchos twitter avatar
    GOAL! Seo-In Kim sends a cross far post and Nick DePuy heads it in to put the Gauchos up 1-0 with 3 minutes left in the half
    10 hours 24 min ago
  • UCSBgauchos twitter avatar
    Women's Soccer: San Jose State 1, UC Santa Barbara 1 (Final - 2OT) UCSB, San Jose State Battle to 1-1 Tie http://t.co/KolrGPE4AY
    10 hours 37 min ago
  • UCSBgauchos twitter avatar
    Big save by Vom Steeg to keep the game scoreless! 25 min left in 1st half @UCSBMensSoccer
    10 hours 49 min ago
  • UCSBgauchos twitter avatar
    Stanford has the advantage in the run of play through 10 minutes but it's still 0-0. @UCSBMensSoccer
    10 hours 57 min ago
  • UCSBgauchos twitter avatar
    WVB: UCSB Opens Season with Back-to-Back Sweeps! #GoGauchos http://t.co/yye1PtugDW
    11 hours 25 min ago
  • UCSBgauchos twitter avatar
    Heres UCSB's starting lineup against Stanford: Vom Steeg, Quezada, Strong, Backus, Jome, Espana, Feucht, Murphy, Acheampong, Selemani, DePuy
    11 hours 25 min ago
  • UCSBgauchos twitter avatar
    Don't miss @UCSBMensSoccer season opener against Stanford. Kickoff in 10 minutes!
    11 hours 33 min ago
  • UCSBgauchos twitter avatar
    @UCSBWomenSoccer ties San Jose St. 1-1 in home season opener behind early goal by Mallory Hromatko
    11 hours 43 min ago
  • UCSBgauchos twitter avatar
    RT @UCSB_Volleyball: Make that two sweeps on opening day! We topped UIW 3-0 and are now 2-0!… https://t.co/iybbM7N1tn
    12 hours 16 min ago

Superconducting Qubit Array Points the Way to Quantum Computers

A new five-qubit array from UCSB’s Martinis Group is on the threshold of making a quantum computer technologically feasible to build
Wednesday, April 23, 2014 - 10:00
Santa Barbara, CA

A fully functional quantum computer is one of the holy grails of physics. Unlike conventional computers, the quantum version uses qubits (quantum bits), which make direct use of the multiple states of quantum phenomena. When realized, a quantum computer will be millions of times more powerful at certain computations than today’s supercomputers.

A group of UC Santa Barbara physicists has moved one step closer to making a quantum computer a reality by demonstrating a new level of reliability in a five-qubit array. Their findings appear Thursday in the journal Nature.

Quantum computing is anything but simple. It relies on aspects of quantum mechanics such as superposition. This notion holds that any physical object, such as an atom or electron — what quantum computers use to store information — can exist in all of its theoretical states simultaneously. This could take parallel computing to new heights.

 “Quantum hardware is very, very unreliable compared to classical hardware,” says Austin Fowler, a staff scientist in the physics department, whose theoretical work inspired the experiments of the Martinis Group. “Even the best state-of-the-art hardware is unreliable. Our paper shows that for the first time reliability has been reached.”

While the Martinis Group has shown logic operations at the threshold, the array must operate below the threshold to provide an acceptable margin of error. “Qubits are faulty, so error correction is necessary,” said graduate student and co-lead author Julian Kelly who worked on the five-qubit array.

“We need to improve and we would like to scale up to larger systems,” said lead author Rami Barends, a postdoctoral fellow with the group. “The intrinsic physics of control and coupling won’t have to change but the engineering around it is going to be a big challenge.”

The unique configuration of the group’s array results from the flexibility of geometry at the superconductive level, which allowed the scientists to create cross-shaped qubits they named Xmons. Superconductivity results when certain materials are cooled to a critical level that removes electrical resistance and eliminates magnetic fields. The team chose to place five Xmons in a single row, with each qubit talking to its nearest neighbor, a simple but effective arrangement.

“Motivated by theoretical work, we started really thinking seriously about what we had to do to move forward,” said John Martinis, a professor in UCSB’s Department of Physics. “It took us a while to figure out how simple it was, and simple, in the end, was really the best.”

“If you want to build a quantum computer, you need a two-dimensional array of such qubits, and the error rate should be below 1 percent,” said Fowler. “If we can get one order of magnitude lower — in the area of 10-3 or 1 in 1,000 for all our gates — our qubits could become commercially viable. But there are more issues that need to be solved. There are more frequencies to worry about and it’s certainly true that it’s more complex. However, the physics is no different.”

 According to Martinis, it was Fowler’s surface code that pointed the way, providing an architecture to put the qubits together in a certain way. “All of a sudden, we knew exactly what it was we wanted to build because of the surface code,” Martinis said. “It took a lot of hard work to figure out how to piece the qubits together and control them properly. The amazing thing is that all of our hopes of how well it would work came true.”

Contact Info: 

Julie Cohen
julie.cohen@ucsb.edu
(805) 893-7220

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