"Our success provides a route to developing new ways to test fundamental aspects of quantum physics and to design new, exotic materials – problems that would be impossible to solve even using today's fastest supercomputers."Sven Rogge, UNSW

In a proof-of-principle experiment, researchers at the University of New South Wales (UNSW) in Australia have shown that a couple of boron atoms placed very precisely in silicon offer a convenient way to study the quantum world. This novel ‘quantum simulator’ could help advance the development of a silicon-based quantum computer and lead to the design of new, exotic materials.

"Previously this kind of exact quantum simulation could not be performed without interference from the environment, which typically destroys the quantum state," says senior author Sven Rogge, head of the UNSW School of Physics and program manager with the ARC Centre of Excellence for Quantum Computation and Communication Technology (CQC2T).

"Our success provides a route to developing new ways to test fundamental aspects of quantum physics and to design new, exotic materials – problems that would be impossible to solve even using today's fastest supercomputers."

The study is published in Nature Communications. The lead author is UNSW's Joe Salfi and the team includes CQC2T director Michelle Simmons, other CQC2T researchers from UNSW and the University of Melbourne, as well as researchers from Purdue University in the US.

The researchers studied two dopant atoms of boron only a few nanometres from each other in a silicon crystal. The boron atoms behaved like they were joined by a valence bond, the ‘glue’ that holds matter together when atoms with unpaired electrons in their outer orbitals overlap and bond.

The team's major advance was directly probing the electron ‘clouds’ around the two atoms, allowing them to measure the energy of the interactions of the spin, or tiny magnetic orientations, of the electrons making up these clouds. They were also able to correlate the interference patterns of the electrons, produced by their wave-like nature, with their entanglement, or mutual dependence on each other for their properties.

"The behavior of the electrons in the silicon chip matched the behavior of electrons described in one of the most important theoretical models of materials that scientists rely on, called the Hubbard model," says Salfi. "This model describes the unusual interactions of electrons due to their wave-like properties and spins. And one of its main applications is to understand how electrons in a grid flow without resistance, even though they repel each other."

The team also made a counterintuitive finding – that the entanglement of the electrons in the silicon chip increased the further they were apart. "This demonstrates a weird behavior that is typical of quantum systems," says Rogge.

"Our normal expectation is that increasing the distance between two objects will make them less, not more, dependent on each other. By making a larger set of dopant atoms in a grid in a silicon chip we could realize a vision first proposed in the 1980s by the physicist Richard Feynman of a quantum system that can simulate nature and help us understand it better."

This story is adapted from material from UNSW, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.