Atomic-scale quantum circuit marks major quantum computer breakthrough
Engineers in Sydney have demonstrated a quantum integrated circuit made up of just a few atoms. By precisely controlling the quantum states of the atoms, the new processor can simulate the structure and properties of molecules in a way that could unlock new materials and catalysts.
The new quantum circuit comes from researchers at the University of New South Wales (UNSW) and a start-up company called Silicon Quantum Computing (SQC). It’s essentially made up of 10 carbon-based quantum dots embedded in silicon, with six metallic gates that control the flow of electrons through the circuit.
It sounds simple enough, but the key lies in the arrangement of these carbon atoms down to the sub-nanometer scale. Relative to each other, they’re precisely positioned to mimic the atomic structure of a particular molecule, allowing scientists to simulate and study the structure and energy states 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 a repeating chain of carbon and hydrogen atoms with an alternating pattern of single and double carbon bonds between them. To simulate those bonds, the team placed the carbon atoms at different distances apart.
Next, the researchers ran an electrical 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 cutting bonds at different places, and the resulting currents matched theoretical predictions perfectly.
The significance of this new quantum circuit, the team says, is that it could be used to study more complicated molecules, which could eventually yield new materials, pharmaceuticals, or catalysts. This 10-atom version is right on the limit of what classical computers can simulate, so the team’s plans for a 20-atom quantum circuit would allow for simulation of more complex molecules for the first time.
“Most of the other quantum computing architectures out there haven't got the ability to engineer atoms with sub-nanometer precision or allow the atoms to sit that close,” said Professor Michelle Simmons, lead researcher on the study. “And so that means that now 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.”
The research was published in the journal Nature.