Scientists use a quantum device to slow a simulated chemical reaction 100 billion times

Scientists at the University of Sydney have, for the first time, used a quantum computer to engineer and control a process crucial in chemical reactions by slowing it down by a factor of 100 billion times.

Joint Principal Investigator and Ph.D. Student Vanessa Olaya Agudelo said: “By understanding these fundamental processes within and between molecules, we can open up a new world of possibilities in materials science, drug design, or solar energy harvesting.

“It could also help improve other processes that depend on the interaction of molecules with light, such as how smog is created or how the ozone layer is damaged.”

Specifically, the research team witnessed the interference pattern of a single atom resulting from a geometric structure common in chemistry called the “conical crossing”.

Conic junctions are known throughout chemistry and are vital to rapid photochemical processes such as light gathering in human vision or photosynthesis.

Chemists have attempted to directly observe such engineering processes in chemical dynamics since the 1950s, but it is not possible to directly observe them due to the extremely fast timescales involved.

To get around this problem, quantum researchers in the Faculty of Physics and Faculty of Chemistry set up an experiment using a quantum computer that trapped ions in a completely new way. This allowed them to model and plot this very complex problem on a relatively small quantum machine, and then slow the process by a factor of 100 billion. The results of their research are published on August 28 Nature’s chemistry.

“In nature, the whole process ends within a femtosecond,” said Olaya Agudelo, from the Faculty of Chemistry. “That’s a billionth of a million – or one quadrillion – of a second.

“Using our quantum computer, we built a system that allowed us to slow down chemical dynamics from femtoseconds to milliseconds. This allowed us to make meaningful observations and measurements.

“This has never been done before.”

“Until now, we have not been able to directly observe the dynamics of the ‘geometric phase’; it occurs too quickly to be investigated experimentally,” said co-lead author Dr. Christoph Valahau from the School of Physics.

“Using quantum technologies, we have addressed this problem.”

It’s like simulating the air patterns around the wing of an airplane in a wind tunnel, Fallaho said.

“Our experiment was not a digital approximation of the process, but rather a direct analog observation of quantum dynamics unfolding at a speed we can observe,” he said.

In photochemical reactions, such as photosynthesis, in which plants get their energy from the sun, molecules transfer energy at lightning speed, forming exchange zones known as conical junctions.

This study has slowed down quantum computer dynamics and revealed the expected—but not previously seen—distinctive features associated with conical junctions in photochemistry.

Co-author and lead researcher, Associate Professor Yvan Casale from the University of Sydney’s School of Chemistry and Nanotechnology Institute, said: “This exciting result will help us better understand ultrafast dynamics – how molecules change at the fastest timescales.”

“It is tremendous that we at the University of Sydney have access to the best programmable quantum computer in the country to perform these experiments.”

The quantum computer used to perform the experiment is housed in the Quantum Control Laboratory of Professor Michael Bircock, founder of quantum start-up Q-CTRL. The experimental effort was led by Dr. Ting Ri Tan.

“This is a wonderful collaboration between chemical theorists and experimental quantum physicists,” said Tan, one of the study’s authors. “We are using a new approach in physics to tackle a long-standing problem in chemistry.”