​University of Melbourne captures electric current movement in graphene

The university's diamond quantum sensor reveals how current flows in 'next-generation' materials like graphene.


Artist's impression of a diamond quantum sensor

Image: David A. Broadway/cqc2t.org

Researchers at the University of Melbourne (UoM) have announced a boost to the development of future electronics, producing imagery of electrons moving in two-dimensional graphene.

In the above image, the spotlight-like shine below the diamond represents light passing through the diamond defect and detecting the movement of electrons. Electrons are shown as red spheres, trailed by red threads that reveal their path through graphene, which is a single layer of carbon atoms

According to the university, the team is the first in the world to image the behaviour of moving electrons in structures that are one atom in thickness, with no one previously able to see what is happening with electric currents in graphene.

The UoM team, led by professor Lloyd Hollenberg, deputy director of the Centre for Quantum Computation and Communication Technology (CQC2T) and Thomas Baker Chair at UoM, used a special quantum probe based on an atomic-sized "colour centre" -- found only in diamonds -- to image the flow of electric currents in graphene.

The university's method includes shining a green laser on the diamond, which produces a red light from the colour centre's response to an electron's magnetic field. By analysing the intensity of the red light, UoM is able to determine the magnetic field created by the electric current and see the effect of material imperfections.

The technique could be used to understand electron behaviour in a variety of new technologies, the university explained.

"Next-generation electronic devices based on ultra-thin materials, including quantum computers, will be especially vulnerable to contain minute cracks and defects that disrupt current flow," Hollenberg said.

"The ability to see how electric currents are affected by these imperfections will allow researchers to improve the reliability and performance of existing and emerging technologies. We are very excited by this result, which enables us to reveal the microscopic behaviour of current in quantum computing devices, graphene, and other 2D materials."

Hollenberg said his team's new sensing technique provides the potential to observe how electrons move in such structures, aiding future understanding of how quantum computers will operate.

In addition to understanding nanoelectronics that control quantum computers, UoM said the technique could be used with 2D materials to develop next generation electronics, batteries, flexible displays, and bio-chemical sensors.

A team of physicists from the Australian National University (ANU) successfully completed an experiment to stop light in September, a critical step in developing future quantum computers.

At the time, the university likened the advancement to a Star Wars endeavour, saying the team performed something similar to the way Kylo Ren used the force to stop a laser blast.

"Optical quantum computing is still a long way off, but our successful experiment to stop light gets us further along the road," said Jesse Everett from the Research School of Physics and Engineering and Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology at ANU. "It's pretty amazing to look at a sci-fi movie and say we actually did something that's a bit like that."

In October, engineers at the University of New South Wales (UNSW) created a new quantum bit (qubit) which remains in a stable superposition for 10 times longer than previously achieved, expanding the time during which calculations could be performed in a future silicon quantum computer.

The new qubit, made up of the spin of a single atom in silicon and merged with an electromagnetic field -- known as a dressed qubit -- retains quantum information for much longer that an "undressed" atom, which opens up new avenues for quantum computer creation.

Another team of UNSW engineers announced a year prior they had built a quantum logic gate in silicon, which made calculations between two qubits of information possible.

At the time, the discovery was called a landmark result not only for Australia, but for the world, as until then it had not been possible to make two quantum bits "talk" to each other and create a logic gate using silicon.

"This result means that all of the fundamental building blocks that are required to make a full scale silicon processor chip are now in place," Andrew Dzurak, scientia professor at the university, said previously. "We're ready to move from this scientific research phase, into the engineering stage and the manufacturing stage."

Building on this breakthrough, another team of researchers out of the university, led by professor Michelle Simmons, unlocked the key to enabling quantum computer coding in silicon, announcing in late 2015 that the team had the capability to write and manipulate a quantum version of computer code using two qubits in a silicon microchip.


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