MIT Researchers Develop New Superconducting Nanowire Device

June 19, 2021 by Stephanie Leonida

Researchers continue to develop a superconducting nanowire to pave the way for more efficient superconducting electronics.

Researchers from the Massachusetts Institute of Technology (MIT) have worked on developing superconductor research from the 1960s to create an innovation. The nano-cryotron could one day be used in quantum computers and other superconducting devices. 


What are Superconductors?

A superconductor can be any material that can conduct electricity or transport electrons from one atom to another without any resistance. Additionally, magnetic flux fields are known to be expelled by such materials. This means that when the material reaches the temperature at which it becomes superconductive, that releases no sound, heat, or other forms of energy. Unlike traditional conductors like steel or copper, superconductors can carry a current indefinitely without losing any energy. Some well-known superconductors include magnesium diboride, aluminum, niobium, cuprates such as yttrium barium copper oxide, and iron pnictides.

Superconductors are used for a variety of different applications. These highly conductive materials can be found in magnetic and nuclear resonance imaging machines and have been used to speed up connections between computer chips. Superconductors are also being used in fast digital circuits, radiofrequency and microwave filters, electric motors and generators, quantum computers, and more. 


The Josephson Junction

A Josephson Junction is a quantum mechanical device that consists of two layers of superconducting material that are separated by a thin insulating layer of non-superconducting material. The Josephson junction is a type of electronic circuit that can switch at high speeds when running at temperatures close to absolute zero. The devices are named after Brian Josephson who predicted that pairs of superconducting electrons could "tunnel" right through the nonsuperconducting barrier from one superconductor to another. Following his predictions that were conceived in the 1960s, Josephson received the Nobel Prize in Physics in 1973. 

In a news release from earlier this year, Professor Karl Berggren from MIT said that the Josephson Junction is what “led to conventional superconducting electronics, and then ultimately to the superconducting quantum computer.” Professor Berggren heads the Quantum Nanostructures and Nanofabrication Group at MIT’s Department of Electrical Engineering and Computer Science.


Professor Karl Berggren. Image used courtesy of MIT
Professor Karl Berggren. Image used courtesy of MIT


Berggren explains that the Josephson Junction is quite a fragile object and can fall short concerning the cost and complexity of manufacturing. Additionally, Berggren went on to say that “If you try to interface it with conventional electronics, like the kinds in our phones or computers, the noise from those just swamps the Josephson junction. So, this lack of ability to control larger-scale objects is a real disadvantage when you're trying to interact with the outside world.”


Buck’s Cryotron

Berggren is working on a new device that is built on the foundations of the work of Dudley Buck. In 1956, Buck published a description of a superconducting computer switch called the cryotron. The device was to be comprised of two superconducting wires. This device was hoped to become the foundation stone for the development of computers. Unfortunately, further work could not go ahead as Buck died at an early age (32) in 1959. 


The Nano-Cryotron

Berggren and his research team are intending to develop a new superconducting nanowire device based on Buck’s ideas. Berggren’s nano-cryotron uses heat to trigger a switch instead of a magnetic field. 

The new device could offer up some advantages over Josephson junction-based superconducting devices in that it is easier to manufacture according to Berggren. Berggren’s group has already demonstrated proof of concept for the use of the nano-cryotron device as an electronic component. The group has used nano-cryotrons in devices to add binary digits and as an interface between superconducting devices and traditional, transistor-based electronics.

Berggren’s group believes that their new device could, one day, be used in quantum computers and supercooled electronics for telescopes. Wires are known to have low power dissipation and so, could be used for energy-demanding applications as well. “It’s probably not going to replace the transistors in your phone, but if it could replace the transistor in a server farm or data center? That would be a huge impact,” said Berggren.