UQ's Quantum Computers Make Light Work of Harvard's Chemistry

UQ physicists and Harvard chemists have teamed up to build a quantum computer that could have profound implications for wider science.

Professor Andrew White and colleagues from UQ's School of Mathematics and Physics, teamed up with researchers from Harvard University, led by Professor Alán Aspuru-Guzik, to tackle the problem of applying quantum mechanics to fields such as chemistry and biology.

“Physicists have a problem,” Professor White said.

“They have an outstandingly successful theory of nature at the small scale – quantum mechanics – but have been unable to apply it exactly to situations more complicated than, say, four or five atoms.

“But now we have done exactly that by building a small quantum computer and used it to calculate the precise energy of molecular hydrogen."

This groundbreaking approach to molecular simulations could have profound implications not just for chemistry, but also for a range of fields from cryptography to materials science.

The work, published this week in Nature Chemistry, saw Professor White's team assemble the physical computer and run the experiments, while Professor Aspuru-Guzik's team coordinated experimental design and performed key calculations.

“We were the software guys and they were the hardware guys,” Professor Aspuru-Guzik said.

While modern supercomputers can perform approximate simulations, increasing the complexity of these systems results in an exponential increase in computational time.

“Quantum computers promise highly precise calculations while using a fraction the resources of conventional computing,” he said.

“This computational power derives from the way quantum computers manipulate information. In classical computers, information is encoded in bits, that have only two values: zero and one. Quantum computers use quantum bits – qubits – that can have an infinite different number of values such as zero, or one, or zero plus one, and so on.

“Quantum computers also exploit the strange phenomena of entanglement, powerful correlations between qubits that Einstein once described as ‘spooky action at a distance'.”

Professor White said it would be a while before quantum computers would leave the lab and appear on desktops.

“It's very early days for quantum technology,” he said.

“Most quantum computer demonstrations have been limited to a handful of qubits. A colleague of mine in Canada says that any demonstration with less than ten qubits is cute but useless, which makes me think of a baby with an abacus.

“However, Alán and his team at Harvard have shown that when we can build circuits of just a few hundred qubits, this will surpass the combined computing power of all the traditional computers in the world, each of which uses many billions of bits.”

“It took standard computing 50 years to get to this point, I'm sure we can do it in much less time than that.”

Professor White's UQ co-authors on the Nature Chemistry paper were Benjamin P. Lanyon, Geoffrey G. Gillet, Michael E. Goggin, Marcelo P. Almeida, Benjamin J. Powell, and Marco Barbieri. Funding was provided by the Australian Research Council Federation Fellow and Centre of Excellence programs, and the US Army Research Office (ARO) and Intelligence Advanced Research Projects Initiative (IARPA).

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