Aussie quantum experiment challenges computer science

University of Queensland and Harvard experiment set to shake science

Australian scientists have completed ground-breaking research using quantum computing that will challenge, among scientific principles, the theory of quantum mechanics.

A joint experiment between the University of Queensland (UQ) and Harvard University, the first of its kind to apply quantum mechanics to chemistry to predict molecular reactions, could have huge implications for science.

UQ physics professor Andrew White, a co-author of the project, said the existence of quantum computing means that either quantum mechanics is wrong, or the Church Turing Thesis, which underpins computer science, is flawed.

“If the Church Turing Thesis is wrong, that’s really big news; or it means that quantum computing will turn out to be impossible for a fundamental reason, or that a fast classical factoring algorithm exists,” White said, referring to a theory by MIT assistant professor Scott Aaronson that the only way to prove the probability of quantum mechanics is to build a quantum computer.

“If you asked [the inventors of the diode] what good they have done, they might have said they can shrink a computer to the size of a living room, but they would never have guessed what computers would become – this is where we are at.

“What we have done is a 2 qubit (quantum bit), toy experiment – it won’t put anyone out of a job anytime soon… but if we scale to tens and then hundreds of qubits, that’s when we will exceed the computational capacity of the planet… that will happen [within] 50 years.”

Due to the nature of science, the ramifications of the experiment are essentially unknown, however, White postulates that it could be used to predict the outcome of chemical reactions, albeit without the inherent randomness that is absent in controlled computer simulations.

He said it is likely that chemistry, rather than cryptography (which requires a prodigious amount of processing) will spearhead quantum computing research.

The experiment ran an algorithm dubbed the iterative phase estimation to measure the precise energy of molecular hydrogen against a predicted model. The results, White said, were "astounding" and were accurate inside of 6 parts in a million. Data was calculated to 20 bits, and in some instances up to 47 bits, and experiments were repeated 30 times for classical error correction.

Quantum computers work "brilliantly" for molecular simulations: Computational power doubles with each qubit, via the phenomena of entanglement, while the complexity of chemical reactions double with each additional atom. Simply put, no other computer, supercomputer, or bunch of supercomputers, could hope to run the simulations to the same degree.

A quantum computer with hundreds of qubits would be more powerful than every traditional computer on Earth, amounting to billions of bits. “A classical computer with 300 bits of can store 300 bits of information, whereas a 300 qubit register can store more information than the number of particles in the universe,” White said.

Scientists involved on the project included Benjamin Lanyon, Geoffrey G. Gillet, Michael E. Goggin, Marcelo P. Almeida, Benjamin J. Powell, Marco Barbieri and Harvard’s Alán Aspuru-Guzik. The experiment was funded by the Australian Research Council Federation Fellow and Centre of Excellence programs, and the US Army Research Office and Intelligence Advanced Research Projects Initiative.

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6 Comments

Daniel Hazelton Waters

1

I believe that 300 qubits could store a number of possible states up to the number of particles in the known universe. But not that they can store info about those particles or that we know how many particles there even is. So without reverse time distortion 300 qubits may not even come close.

David-Sarah Hopwood

2

"Andrew White, a co-author of the project, said the existence of quantum computing means that either quantum mechanics is wrong, or the Church Turing Thesis, which underpins computer science, is flawed."

Absolute nonsense. The Church-Turing thesis, in any of its formulations (and White really should say which one he means), is only about what computations are possible for an idealized computer, not about their efficiency. Quantum computation only changes efficiency.

Lauri Pirttiaho

3

"“A classical computer with 300 bits of can store 300 bits of information, whereas a 300 qubit register can store more information than the number of particles in the universe,” White said."

You have to remenber that the essential differentiating feature of a quantum computer compared to a conventional one is how it does computation, not the amount of information it can store. In fact, you can not use quantum computer (that is, the processor doing the computation) to store information (except for short time during the computation) since it is not a storage device, just like a processor in a conventional computer is not a storage device.

One should not confuse the different aspects of information handling: processing, transport and storage. Quantum phenomena have found applications in the first two but has been a source of problems in the third one.

For enlightening introduction, please take a look at N.D. Mermin's excellent intorduction to the field in his book "Quantum Computer Science, An Introduction".

Rabinder Koul

4

The quantum computing implies existence of all possible possible states, instead of Yes or no binary logic. I believe it is here that Turing machin cocept of computation gets challenged.

Stephen Fenner

5

The article's mention of a threat to the Church-Turing thesis is misleading. There is nothing in their paper (that I can see) that threatens the original thesis. Quantum computing itself would require a revision to a strong form of the thesis, but this has been known for decades.

Sampanthan

6

To be honest, I smell COLD FUSION.

Sure many things are possible,
Sure if one could have asked Miss Lucy, she wouldn't have had
a clue, and she might have even laughed at the idea of Homo- Sapiens wearing clothes, forget even worrying about Quantum, Relativity and Cold Fusion in a world where scientists are hungry for grant money. Say anything, most people are gullible.

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