The birth of atomic-level quantum circuits marks a major breakthrough in quantum computer technology

Engineers in Sydney have demonstrated a quantum integrated circuit made of just a few atoms. By precisely controlling the quantum state of atoms, this new processor can simulate the structure and properties of molecules, unlocking new materials and catalysts. The new quantum circuit comes from researchers at the University of New South Wales (UNSW) and a startup called Silicon Quantum Computing (SQC).

It basically consists of 10 carbon-based quantum dots embedded in silicon, with six metal gates controlling the flow of electrons in a circuit.

It sounds simple enough, but the key is that these carbon atoms are arranged at the subnanometer scale. Relative to each other, they are precisely positioned to mimic the atomic structure of a specific molecule and allow scientists to simulate and study the structure and energy state of that molecule more accurately than ever before.

In this case, they arranged the carbon atoms into the shape of the organic compound polyacetylene, which is made up of repeating chains of carbon and hydrogen atoms with an alternating single and double carbon bond between them. To mimic these bonds, the team placed the carbon atoms at varying distances.

Next, the researchers ran an electric current through the circuit to check whether it would match the signature of a natural polyacetylene molecule—and sure enough, it did. In other tests, the team created two different versions of the chain by severing bonds in different places, and the resulting currents matched theoretical predictions exactly.

The research team said the significance of this new quantum circuit is that it can be used to study more complex molecules, which may eventually lead to new materials, drugs or catalysts. This 10-atom version is right at the limit of what can be simulated by classical computers, so the team's 20-atom quantum circuit plan will allow the simulation of more complex molecules for the first time.

Professor Michelle Simmons, lead researcher on the study, noted: "Most other quantum computing architectures don't have the ability to design atoms with sub-nanometer precision, or to have atoms sit so close together. So what this means is that now we can start to understand more and more complex molecules based on putting atoms in place, just like we would mimic real physical systems."