Researchers put a twist on graphene by producing quantum device

The research team said the new device broadens the potential applications that graphene could be used for in the future.

Researchers in Switzerland have developed a quantum device using graphene, broadening the potential applications of this ‘wonder material’.

Graphene is a one-atom-thick layer of carbon that is 200 times stronger than steel, yet extremely flexible. It is considered to be one of the world’s thinnest and strongest materials, and there are many potential applications due to its flexibility and conductivity.

Last year, a team from ETH Zurich demonstrated that twisted graphene could be used to create Josephson junctions, which are important for superconducting devices.

Building on this work, researchers have now used twisted graphene to produce a superconducting quantum interference device, or Squid.

Squids can host quantum bits, or elements for carrying out quantum operations. These devices are based on a superconducting loop containing Josephson junctions and can measure tiny changes in magnetic fields.

The researchers said conventional Squids are already being used in sectors such as medicine, geology and archaeology.

“Squids are to superconductivity what transistors are to semiconductor technology – the fundamental building blocks for more complex circuits,” said Prof Klaus Ensslin, one of the study leaders.

The new graphene devices created by doctoral student Elías Portolés are not more sensitive than their conventional counterparts, which are made from aluminium. Ensslin said this means the result is not “a breakthrough for Squid technology”.

However, the team said the result broadens the potential applications that graphene could be used for in the future.

“Five years ago, we were already able to show that graphene could be used to build single-electron transistors,” Ensslin said. “Now we’ve added superconductivity.”

There are some notable improvements using graphene for these quantum devices. The team said the graphene’s behaviour can be controlled in a targeted manner by biasing an electrode. The material can be insulating, conducting or superconducting, based on the voltage applied.

The researchers said this result also means semiconductors and superconductors can now be combined in a single material, which makes it possible to build novel control operations.

“Normally, the transistor is made from silicon and the Squid from aluminium,” Ensslin explained. “These are different materials requiring different processing technologies.”

The research team is focused on future possibilities. Ensslin said different qubit technologies are being assessed and that if two of these systems are coupled using graphene, it could be possible to combine their benefits as well. This could generate new possibilities for research into superconductivity.

The research team also believes the results could lead to new devices being developed in the future.

“We envision our findings, together with the established history of applications Squids have, will foster the development of a wide range of devices such as phase-slip junctions or high kinetic inductance detectors,” the researchers said in their study, published in Nature Nanotechnology.

There are many potential applications when it comes to graphene. In March, researchers in Sweden claimed to have achieved high conductivity for a type of graphene that is manufactured in a simpler and cheaper method, which could lead to a “new era” of flexible electronics.

Earlier this year, scientists in Ireland said they had developed a low-cost method to produce graphene ink, which could reduce the production cost of graphene to £20 per litre once scaled up.

Trinity College Dublin nanoscientist Prof Jonathan Coleman previously created nanocomposites of graphene with polymers including those found in rubber bands and silly putty. Last year, his team created a graphene ink blend with excellent mechanical and electrical properties, giving it potential in the wearables space.

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