August 17, 2022

A quantum processor to emulate a small organic molecule

A quantum processor to emulate a small organic molecule

A team of quantum computer physicists at UNSW Sydney has engineered a quantum processor at the atomic scale to simulate the behavior of a small organic molecule, solving a challenge set some 60 years ago by theoretical physicist Richard Feynman.

The achievement represents a major milestone in the race to build the world’s first quantum computer, and demonstrates the team’s ability to control the quantum states of electrons and atoms in silicon at an exquisite level not achieved before.

The team able to mimic the structure and energy states of the organic compound polyacetylene—a repeating chain of carbon and hydrogen atoms distinguished by alternating single and double bonds of carbon.

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

To be doubly sure, they simulated two different strands of the polymer chains.

In the first device they cut a snippet of the chain to leave double bonds at the end giving 10 peaks in the current. In the second device they cut a different snippet of the chain to leave single bonds at the end only giving rise to two peaks in the current. The current that passes through each chain was therefore dramatically different due to the different bond lengths of the atoms at the end of the chain. (

Not only did the measurements match the theoretical predictions, they matched perfectly.

The paper has been published in the journal Nature.

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