A team of quantum computer physicists at the University of New South Wales in Australia has designed an atomic-scale quantum processor that can simulate the behavior of small organic molecules, overcoming a challenge posed by theoretical physicist Richard Feynman some 60 years ago. The university's startup Silicon Quantum Computing (SQC) announced on June 23 that it has created the world's first atomic-scale quantum integrated circuit.

According to SQC's website, the team announced in 2012 that it had created the world's first single-atom transistor, and proposed to achieve atomic-level quantum integrated circuits by 2023. Now, that goal has been achieved ahead of schedule.

After fabricating an atomic-scale integrated circuit to be used as a simulated quantum processor, the SQC team used this quantum processor to accurately simulate the quantum state of a small organic polyacetylene molecule, thus demonstrating the effectiveness of their quantum system modeling technique. By precisely controlling the quantum state of the atom, the new processor can simulate the structure and properties of the molecule, promising to help scientists "unlock" new materials and catalysts of the future.

In the paper, the researchers describe how they simulated the structure and energy states of the organic compound polyacetylene. Polyacetylene is a repetitive chain of carbon and hydrogen atoms, with alternating single and double bonds between carbon and carbon. The team constructed a quantum integrated circuit of 10 quantum dot chains to simulate the precise position of atoms in the polyacetylene chain, where six metal gates control the flow of electrons in the circuit.

According to lead researcher and SQC founder Michele Simmons, the choice of a 10-atom carbon chain was not accidental because it was within the size limit of what a classical computer can calculate, with up to 1,024 independent interactions of electrons in the system. Increasing to a 20-point chain would increase the number of possible interactions exponentially, which would make it difficult for a classical computer to solve.

"In the 1950s, Feynman suggested that you can't understand how nature works unless you can build matter at the same scale." Simmons says, "That's what we're doing, and we're actually building it from the bottom up, by putting atoms into silicon to model polyacetylene molecules with precise distances representing carbon-carbon single bonds and carbon-carbon double bonds."

Simmons sees this as a major breakthrough. Today's classical computers have difficulty simulating relatively small molecules because of the large number of interactions possible between atoms. the development of SQC's atomic-level circuit technology will allow the company and its customers to build quantum models for a range of new materials, whether they are pharmaceuticals, battery materials or catalysts.