Quantum computer slows chemical process by factor of 100bn

Scientists at The University of Sydney have used a quantum computer to engineer and directly observe a process critical in chemical reactions by slowing it down by a factor of 100 billion times, in what is said to be a world first. Specifically, the research team witnessed the interference pattern of a single atom caused by a common geometric structure in chemistry called a ‘conical intersection’.

In rapid photochemical processes such as photosynthesis, molecules transfer energy at lightning speed, forming areas of exchange known as conical intersections. Chemists have tried to directly observe such geometric processes in chemical dynamics since the 1950s, but it is not feasible to observe them directly given the extremely rapid timescales involved.

“In nature, the whole process is over within femtoseconds,” said joint lead researcher Vanessa Olaya Agudelo. “That’s a billionth of a millionth — or one quadrillionth — of a second.”

To get around this problem, the researchers created an experiment using a trapped-ion quantum computer — based in the Quantum Control Laboratory of Professor Michael Biercuk — in a completely new way. This allowed them to design and map this very complicated problem onto a relatively small quantum device — and then slow the process down by a factor of 100 billion. Their findings were published in the journal Nature Chemistry.

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

“This has never been done before.”

Joint lead author Dr Christophe Valahu said the team’s experiment was akin to simulating the air patterns around a plane wing in a wind tunnel. “Our experiment wasn’t a digital approximation of the process — this was a direct analogue observation of the quantum dynamics unfolding at a speed we could observe,” he explained.

By slowing down the dynamics in the quantum computer, the researchers revealed the telltale hallmarks predicted — but never before seen — associated with conical intersections in photochemistry. According to research team leader Associate Professor Ivan Kassal, “This exciting result will help us better understand ultrafast dynamics — how molecules change at the fastest timescales.”

Olaya Agudelo added, “It is by understanding these basic processes inside and between molecules that 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 rely on molecules interacting with light, such as how smog is created or how the ozone layer is damaged.”

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