World's smallest silicon wire brings quantum computers closer to reality

World's thinnest silicon wire, which is just one atom tall and four atoms wide, may play a vital role in developing quantum computers in future, researchers say.  

The wire created by a team of researchers from the University of New South Wales, Melbourne University and Purdue University has the same current-carrying capability as copper wires.

Experiments and atom-by-atom supercomputer models of the wires have found that the wires maintain a low capacity for resistance despite being more than 20 times thinner than conventional copper wires in microprocessors.

Bent Weber, the paper’s lead author and a graduate student in the Centre of Excellence for Quantum Computation and Communication Technology at the University of New South Wales, was thrilled with the finding.

“It’s extraordinary to show that Ohm’s Law, such a basic law, still holds even when constructing a wire from the fundamental building blocks of nature - atoms,” he said.

The innovation of the Australian group was to build the circuits up atom by atom, instead of the current method of building microprocessors, in which material is stripped away, said Gerhard Klimeck, a Purdue professor of electrical and computer engineering and director of the Network for Computational Nanotechnology.

“Typically we chip or etch material away, which can be very expensive, difficult and inaccurate,” Klimeck stated.

“Once you get to 20 atoms wide you have atomic fluctuations that make scaling difficult.

“But this experimental group built devices by placing atomically thin layers of phosphorus in silicon and found that with densely doped phosphorus wires just four atoms wide it acts like a wire that conducts just as well as metal,” he said.

Michelle Simmons, director of the Centre of Excellence for Quantum Computation and Communication Technology at the University of New South Wales and the project’s principal investigator asserted that the goal of the research is to develop future quantum computers in which single atoms are used for the computation.

“We are on the threshold of making transistors out of individual atoms,” Simmons said.

“But to build a practical quantum computer we have recognized that the interconnecting wiring and circuitry also needs to shrink to the atomic scale," Simmons added.

The study has been published in journal Science.