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