From University of Copenhagen: “University of Copenhagen researchers realize new platform for future quantum computer”

From University of Copenhagen

Niels Bohr Institute bloc

Niels Bohr Institute

26 April 2019

Antonio Fornieri
Postdoc
antonio.fornieri@nbi.ku.dk
http://www.nbi.ku.dk/
Phone: +45 35 33 48 89

Michael Skov Jensen
Press officer
Faculty of Science
msj@science.ku.dk
+45 93 56 58 97

Quantum physics

University of Copenhagen physicists, as part of the University and Microsoft collaboration focused on topological quantum computing, may have unloosed a Gordian knot in quantum computer development. In partnership with researchers from University of Chicago, ETH Zürich, Weizmann Institute of Science, and fellow Microsoft Quantum Lab collaborators at Purdue University, they have designed and realized a promising building block for supercomputers of the future: a two-dimensional platform for that could lead to quantum bits that are both stable and able to be mass produced.

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Led by two young physicists, Antonio Fornieri and Alex Whiticar, under the supervision of Professor Charles Marcus, Director of Microsoft Quantum Lab Copenhagen, researchers at the Center for Quantum Devices (QDev) a Center of Excellence sponsored by the Danish National Research Foundation at the Niels Bohr Institute, University of Copenhagen, designed, built, and characterized a key component that could cut a Gordian knot in the development of viable quantum computers – specifically, the building block for a quantum bit, or qubit, that is both protected from disturbances and able to be mass produced. Their results have just been published in the scientific journal, Nature.

Together with a back-to-back publication from a team at Harvard University on a related system, the Copenhagen team was able to demonstrate Majorana zero modes in the one-dimensional semiconductor gap between two superconductors forming a spatially extended Josephson junction, an effect predicted theoretically by teams at Harvard-Weizmann, and Niels Bohr Institute-Lund University.

The wide Josephson junction is part of a complex chip of hybrid superconductor and semiconductor materials grown by Michael Manfra’s Microsoft Quantum Lab group at Purdue. It is anticipated to be an important component in the development of topological quantum information. The discovery unlocks a range of possibilities for researchers. “A major advantage of the discovered component is that it can be mass produced. We can design a large and complex system of quantum bits on a contemporary laptop and have it manufactured using a common production technique for ordinary computer circuits,” says co-lead author Postdoctoral Fellow Antonio Fornieri.

From handcraft to mass production

Majorana quantum states are the foundation for the quantum computer being developed by a combination of University students, PhDs and postdocs, and Microsoft employees pursuing collaborative research at Microsoft Quantum Lab Copenhagen at the Niels Bohr Institute. The Majorana quantum state has an important property that protects it from external disturbances, in principle enabling longer periods of quantum processing compared with other types of quantum bits. One of the greatest challenges for researchers worldwide is to develop qubits that are stable enough to allow a computer to perform complicated calculations before the quantum state disappears and the information stored in the bits is lost.

In the past decade, Majorana particles have been created in the lab using semiconductor nanowires connected to superconductors and placed in a large magnetic field. Nanowires are not well suited for scale-up to a full-blown quantum technology because of the laborious assembly required to manipulate microscopic threads with a needle, move them individually from one substrate to another, and then secure them into a network. Given that a quantum computer will likely require thousands or more bits, this would be an exceptionally difficult process using hand-placed nanowires. Furthermore, nanowires require high magnetic fields to function. The new Josephson junction-based platform replaces the nanowires with a two-dimensional device which requires lower magnetic fields to form the Majorana states.

Promising structure

“Our prototype is a significant first step towards using this type of system to make quantum bits that are protected from disturbances. Right now, we still need some fine-tuning – we can improve the design and materials. But it is a potentially perfect structure,” asserts Fornieri.

The two-dimensional system has another important quality according to research group member Alex Whiticar, a doctoral student: “Our component has an additional control parameter, in the form of the superconducting phase difference across the Josephson junction that makes it possible to simultaneously control the presence of Majorana-states throughout a system of quantum bits. This has never been seen before. Furthermore, this system needs a much lower magnetic field to achieve Majorana states. This will significantly ease the manufacturing of larger quantities of quantum bits.”

Charles Marcus adds, “Moving from one dimensional nanowires into two-dimensional hybrids opened the field. This device is the first of many advances that can be anticipated once topological structures can be patterned and repeated with precision on the 10nm scale. Stay tuned.”

Collaborative public-private partnering

This breakthrough underscores the productiveness of the deepened collaboration established September of 2017 between the University of Copenhagen and Microsoft. This collaboration has only intensified and expanded with the establishing of Microsoft Quantum Materials Lab Copenhagen just one year after, drawing from talent both the University of Copenhagen, the Technical University of Denmark, and around Europe.

As summarized by Michael Manfra, “The close collaboration between the Microsoft Quantum Laboratories has resulted in a promising new platform for the study and control of Majorana zero modes. It is exciting that this approach is potentially scalable.”

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Schematic representation of the device.

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Niels Bohr Institute Campus

The Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient