Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

'Immunizing' quantum bits so that they can grow up

27.02.2019

New material enhances supercurrent in topological-insulator nanoribbon Josephson junctions

Quantum computers will process significantly more information at once compared to today's computers. But the building blocks that contain this information - quantum bits, or "qubits" - are way too sensitive to their surroundings to work well enough right now to build a practical quantum computer.


A new material could 'immunize' topological quantum bits so that they are resilient enough for building a quantum computer.

Credit: Purdue University image/Morteza Kayyalha


An enhanced supercurrent on the surface of this device's topological insulator could bring special properties that make qubits more resilient.

Credit: Purdue University image/Morteza Kayyalha

Long story short, qubits need a better immune system before they can grow up.

A new material, engineered by Purdue University researchers into a thin strip, is one step closer to "immunizing" qubits against noise, such as heat and other parts of a computer, that interferes with how well they hold information. The work appears in Physical Review Letters.

The thin strip, called a "nanoribbon," is a version of a material that conducts electrical current on its surface but not on the inside - called a "topological insulator" - with two superconductor electrical leads to form a device called a "Josephson junction."

In a quantum computer, a qubit "entangles" with other qubits. This means that reading the quantum information from one qubit automatically affects the result from another, no matter how far apart they are.

Without entanglement, the speedy calculations that set apart quantum computing can't happen. But entanglement and the quantum nature of the qubits are also sensitive to noise, so they need extra protection.

A topological-insulator nanoribbon Josephson junction device is one of many options researchers have been investigating for building more resilient qubits. This resilience could come from special properties created by conducting a supercurrent on the surface of a topological insulator, where an electron's spin is locked to momentum.

The problem so far is that a supercurrent tends to leak into the inside of topological insulators, preventing it from flowing completely on the surface.

To get more resilient, topological qubits need supercurrents to flow through the surface channels of topological insulators.

"We have developed a material that is really clean, in the sense that there are no conducting states in the bulk of the topological insulator," said Yong Chen, a Purdue professor of physics and astronomy and of electrical and computer engineering, and the director of the Purdue Quantum Science and Engineering Institute. "Superconductivity on the surface is the first step for building these topological quantum computing devices based on topological insulators."

Morteza Kayyalha, a former Ph.D. student in Chen's lab, could show that the supercurrent wraps all the way around the new topological insulator nanoribbon at temperatures 20 percent lower than the "critical temperature," when the junction becomes superconducting. The experiment was conducted in collaboration with the lab of Leonid Rokhinson, a Purdue professor of physics and astronomy.

"It's known that as the temperature lowers, the superconductivity is enhanced," Chen said. "The fact that much more supercurrent flowed at even lower temperatures for our device was evidence that it is flowing around these protective surfaces."

###

This work was supported by multiple awards from the National Science Foundation, U.S. Department of Energy, U.S. Department of Defense Office of Naval Research and the Simons Foundation.

ABSTRACT

Anomalous Low-Temperature Enhancement of Supercurrent in Topological-Insulator Nanoribbon Josephson Junctions: Evidence for Low-Energy Andreev Bound States

Morteza Kayyalha1, Mehdi Kargarian2, Aleksandr Kazakov1, Ireneusz Miotkowski1, Victor M. Galitski2, Victor M. Yakovenko2, Leonid P. Rokhinson1, and Yong P. Chen1

1Purdue University, West Lafayette, IN, USA

2University of Maryland, College Park, MD, USA

doi: 10.1103/PhysRevLett.122.047003

We report anomalous enhancement of the critical current at low temperatures in gate-tunable Josephson junctions made from topological insulator BiSbTeSe2 nanoribbons with superconducting Nb electrodes. In contrast to conventional junctions, as a function of the decreasing temperature T, the increasing critical current Ic exhibits a sharp upturn at a temperature T* around 20% of the junction critical temperature for several different samples and various gate voltages. The Ic vs Tdemonstrates a short junction behavior for T>T*, but crosses over to a long junction behavior for T<T∗ with an exponential T dependence Ic∝exp(−kBT/δ), where kB is the Boltzmann constant. The extracted characteristic energy scale δ is found to be an order of magnitude smaller than the induced superconducting gap of the junction. We attribute the long-junction behavior with such a small δ to low-energy Andreev bound states arising from winding of the electronic wave function around the circumference of the topological insulator nanoribbon.

Media Contact

Kayla Wiles
wiles5@purdue.edu
765-494-2432

 @PurdueUnivNews

http://www.purdue.edu/ 

Kayla Wiles | EurekAlert!
Further information:
https://www.purdue.edu/newsroom/releases/2019/Q1/immunizing-quantum-bits-so-that-they-can-grow-up.html
http://dx.doi.org/10.1103/PhysRevLett.122.047003

More articles from Materials Sciences:

nachricht From foam to bone: Plant cellulose can pave the way for healthy bone implants
19.03.2019 | University of British Columbia

nachricht Additive printing processes for flexible touchscreens: increased materials and cost efficiency
19.03.2019 | INM - Leibniz-Institut für Neue Materialien gGmbH

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Magnetic micro-boats

Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.

The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...

Im Focus: Self-healing coating made of corn starch makes small scratches disappear through heat

Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.

Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...

Im Focus: Stellar cartography

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...

Im Focus: Heading towards a tsunami of light

Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.

"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...

Im Focus: Revealing the secret of the vacuum for the first time

New research group at the University of Jena combines theory and experiment to demonstrate for the first time certain physical processes in a quantum vacuum

For most people, a vacuum is an empty space. Quantum physics, on the other hand, assumes that even in this lowest-energy state, particles and antiparticles...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

To proliferate or not to proliferate

21.03.2019 | Life Sciences

Magnetic micro-boats

21.03.2019 | Physics and Astronomy

Motorless pumps and self-regulating valves made from ultrathin film

21.03.2019 | HANNOVER MESSE

VideoLinks
Science & Research
Overview of more VideoLinks >>>