Scientists emulate nature in quantum leap towards computers of the future
Lead researcher and former Australian of the Year, Scientia Professor Michelle Simmons. Credit: SQC

A group of quantum computer physicists at the University of New South Wales have created a quantum processor at the atomic scale to mimic the behavior of a small organic molecule.

A major milestone in the race to build the world's first quantum computer was achieved two years ahead of schedule.

The structure and energy states of the organic compound polyacetylene were described in a paper published today in the journal Nature.

The team at Silicon Quantum Computing built a quantum integrated circuit that mimicked the location of atoms in the polyacetylene chain.

Prof. Simmons said that Richard Feynman said you can't understand nature if you can't build matter at the same length scale.

We are replicating the polyacetylene molecule by putting atoms in Silicon with the exact distances that represent the single and double carbon-carbon bonds.

A chain of events.

The research relied on measuring the electric current through a deliberately engineered 10-quantum dot replica of the polyacetylene molecule as each new electron moved from the source outlet to the drain.

They did a simulation of two strands of the chain.

They left double bonds at the end of the chain in the first device. They left single bonds at the end of the chain in the second device, which caused two peaks in the current. Due to the different bond lengths of the atoms at the end of the chain, the current that passes through each chain was vastly different.

The measurement matches the predictions perfectly.

It shows that you can literally mimic what happens in the molecule. The signatures of the two chains are very different.

Most of the other quantum computing architectures do not have the ability to engineer atoms with sub-nanometer precision.

It means that we can start to understand more and more complicated Molecules based on putting the atoms in place as if they're mimicking the real physical system.

There is a person standing at the edge.

Prof. Simmons said that the carbon chain of 10 atoms was chosen because it was within the size limit of a classical computer. Increasing it to a 20-dot chain would make it hard for a computer to solve problems.

She says that stepping off the edge into the unknown is like stepping off a cliff.

We can now make larger devices that are beyond what a computer can model. We can look at compounds that have never been tested before. We're going to be able to understand the world in a different way.

Understanding and mimicking photosynthesis is one of the questions Prof. Simmons mentioned. Understanding how to improve the design of catalysts is currently a high-energy, high- cost process.

There are big implications for understanding how nature works.

A future quantum computer.

The billion-dollar question has always been when can we see a quantum computer.

The development of quantum computers is similar to how classical computers evolved from a transistor in 1947 to an integrated circuit in 1958, and then small computing chips that went into commercial products around five years later.

Prof. Simmons says that they are replicating that road map for quantum computers.

A single atom transistor was the first thing we started with. The equivalent of the atom-scale quantum integrated circuit will be realized in 2021. Five years from now, if we map it to the evolution of classical computing, we should have a commercial result from our technology.

One of the advantages that the UNSW/SQC team's research brings is that the technology isScalable because it manages to use less components in the circuit to control the qubits.

"You need something that creates the qubits, some kind of structure in the device that allows you to form the quantum state," Professor Simmons says.

Our system requires less elements in the circuits than other systems. In order to control the electrons in our 10-dot system, we only needed six metallic gates. Most quantum computing architectures need more than one control system to move the electrons.

The amount of interference with the quantum states can be minimized by packing fewer components together tightly.

It shows that we have a nice clean system that we can manipulate, keeping coherence across long distances with minimal overhead in the gates. That's why it's useful.

Prof. Simmons and her colleagues will look at larger compounds that have never been fully understood before, such as high temperature superconductors.

More information: M. Kiczynski et al, Engineering topological states in atom-based semiconductor quantum dots, Nature (2022). DOI: 10.1038/s41586-022-04706-0 Journal information: Nature