Nov 162017

The new nonreciprocal device acts as a roundabout for photons.
Here, arrows show the direction of photons propagation.
Credit: IST Austria/Birgit Rieger

Researchers at IST Austria have built compact photon directional devices. Their micrometer-scale, nonmagnetic devices route microwave photons and can shield qubits from harmful noise.

Qubits, or quantum bits, are the key building blocks that lie at the heart of every quantum computer. In order to perform a computation, signals need to be directed to and from qubits. At the same time, these qubits are extremely sensitive to interference from their environment, and need to be shielded from unwanted signals, in particular from magnetic fields. It is thus a serious problem that the devices built to shield qubits from unwanted signals, known as nonreciprocal devices, are themselves producing magnetic fields. Moreover, they are several centimeters in size, which is problematic, given that a large number of such elements is required in each quantum processor. Now, scientists at the Institute of Science and Technology Austria (IST Austria), simultaneously with competing groups in Switzerland and the United States, have decreased the size of nonreciprocal devices by two orders of magnitude. Their device, whose function they compare to that of a traffic roundabout for photons, is only about a tenth of a millimeter in size, and—maybe even more importantly—it is not magnetic. Their study was published in the open access journal Nature Communications. (DOI: 10.1038/s41467-017-01304-x)

When researchers want to receive a signal, for instance a microwave photon, from a qubit, but also prevent noise and other spurious signals from traveling back the same way towards the qubit, they use nonreciprocal devices, such as isolators or circulators. These devices control the signal traffic, similar to the way traffic is regulated in everyday life. But in the case of a quantum computer, it is not cars that cause the traffic but photons in transmission lines. “Imagine a roundabout in which you can only drive counterclockwise”, explains first author Dr. Shabir Barzanjeh, who is a postdoc in Professor Johannes Fink’s group at IST Austria. “At exit number one, at the bottom, there is our qubit. Its faint signal can go to exit number two at the top. But a signal coming in from exit number two cannot travel the same path back to the qubit. It is forced to travel in a counterclockwise manner, and before it reaches exit one, it encounters exit three. There, we block it and keep it from harming the qubit.”

The ‘roundabouts’ the group has designed consist of aluminum circuits on a silicon chip and they are the first to be based on micromechanical oscillators: Two small silicon beams oscillate on the chip like the strings of a guitar and interact with the electrical circuit. These devices are tiny in size—only about a tenth of a millimeter in diameter—, one of the major advantages the new component has over its traditional predecessors, which were a few centimeters wide.

Currently, only a few qubits have been used to test the principles of quantum computers, but in the future, thousands or even millions of qubits will be connected together, and many of these qubits will require their own circulator. “Imagine building a processor that has millions of such centimeter-size components. It would be enormous and impractical,” says Shabir Barzanjeh. “Using our nonmagnetic and very compact on-chip circulators instead makes life a lot easier.” Yet some hurdles need to be overcome before the devices will be used for this specific application. For example, the available signal bandwidth is currently still quite small, and the required drive powers might harm the qubits. However, the researchers are confident that these problems will turn out to be solvable.

Learn more: Essential quantum computer component downsized by two orders of magnitude


The Latest on: Quantum computing
  • Check out these 5 wild and wacky quantum computer facts for cool people
    on February 24, 2018 at 9:33 am

    Quantum computers are getting popular, and all the cool publications are writing about them. But, for the most part, it’s all very serious and cautious reporting. That’s a shame, because quantum mechanics are wild and wacky. So, let’s have some fun. […]

  • Getting Your Mind Around Quantum Computing
    on February 23, 2018 at 9:10 pm

    Is five years beyond your investment horizon? If so, ignore what I’m about to say: In five years, we will have practical quantum computers, long the holy grail of computer scientists. That prediction comes from Microsoft (ticker: MSFT), which is pursuing ... […]

  • Serious quantum computers are finally here. What are we going to do with them?
    on February 23, 2018 at 9:04 pm

    Inside a small laboratory in lush countryside about 50 miles north of New York City, an elaborate tangle of tubes and electronics dangles from the ceiling. This mess of equipment is a computer. Not just any computer, but one on the verge of passing what ... […]

  • Blockchain and Quantum Computing
    on February 23, 2018 at 11:58 am

    2018 promises great inroads in the realm of “quantum computing.” While conventional computers use binary data or bits (i.e., 0s and 1s) to store and process information (a bit can either store a 0 or 1), a quantum computer operates based on the laws of ... […]

  • Quantum computing is finally here, and a Canadian company has a plan to bring it to the masses
    on February 23, 2018 at 10:02 am

    After recently closing $50 million in financing, D-Wave Systems is looking to bring in hundreds of millions of dollars more. The company has plans to bring quantum computing to the public cloud this year. As CEO of D-Wave Systems, Brownwell has been ... […]

  • Rigetti Computing Releases Forest 1.3 Quantum Software Platform
    on February 23, 2018 at 12:00 am

    Rigetti Computing has released a new version of Forest, their quantum software platform. Forest 1.3 offers upgraded developer tools, improved stability, and faster execution. Starting today, researchers using Forest will be upgraded to version 1.3, which ... […]

  • A simple guide to quantum computing – in less than four minutes
    on February 22, 2018 at 10:33 pm

    It would take today’s computers billions of years to solve the world’s most complex problems, whereas a quantum computer could provide answers in just a few hours. This has massive implications for research in healthcare, energy, environmental systems ... […]

  • 20 Mind-Boggling Facts About Quantum Computing Everyone Should Read
    on February 22, 2018 at 8:28 pm

    The dream of “quantum computing” – harnessing the power of quantum-level mechanics in order to create computers far faster and more powerful than any available today – came a step closer to reality recently. Microsoft and Google both have just ... […]

  • Quantum computers go silicon
    on February 22, 2018 at 6:27 pm

    For quantum computers, silicon’s springtime may finally have arrived. Silicon-based technology is a late bloomer in the quantum computing world, lagging behind other methods. Now for the first time, scientists have performed simple algorithms on a ... […]

  • Global Quantum Computing Applications, Software and End-user Markets 2018-2028 with Profiles of Leading Quantum Software and Cloud Services Firms
    on February 22, 2018 at 5:30 am

    The "Quantum Computing: Applications, Software and End-user Markets" report has been added to's offering. This report examines the major applications for quantum computers. This report will also provide a ten-year forecast of ... […]

via Google News and Bing News

Other Interesting Posts

Leave a Reply

%d bloggers like this: