Quantum computers will be able to simulate particle collisions (w/ Video)

Jun 01, 2012 By Chad Boutin

(Phys.org) -- Quantum computers are still years away, but a trio of theorists has already figured out at least one talent they may have. According to the theorists, including one from the National Institute of Standards and Technology (NIST), physicists might one day use quantum computers to study the inner workings of the universe in ways that are far beyond the reach of even the most powerful conventional supercomputers.

Quantum computers require technology that may not be perfected for decades, but they hold great promise for solving complex problems. The switches in their will take advantage of quantum mechanics – the laws that govern the interaction of subatomic particles. These laws allow quantum switches to exist in both on and off states simultaneously, so they will be able to consider all possible solutions to a problem at once.

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This unique talent, far beyond the capability of today's computers, could enable quantum computers to solve some currently difficult problems quickly, such as breaking complex codes. But they could look at more challenging problems as well.

"We have this theoretical model of the quantum computer, and one of the big questions is, what physical processes that occur in nature can that model represent efficiently?" said Stephen Jordan, a theorist in NIST's Applied and Computational Mathematics Division. "Maybe particle collisions, maybe the early after the Big Bang? Can we use a quantum computer to simulate them and tell us what to expect?"

Questions like these involve tracking the interaction of many different elements, a situation that rapidly becomes too complicated for today's most powerful computers.

The team developed an algorithm – a series of instructions that can be run repeatedly – that could run on any functioning quantum computer, regardless of the specific technology that will eventually be used to build it. The algorithm would simulate all the possible interactions between two elementary particles colliding with each other, something that currently requires years of effort and a large accelerator to study.

Simulating these collisions is a very hard problem for today's digital computers because the quantum state of the colliding particles is very complex and, therefore, difficult to represent accurately with a feasible number of bits. The team's algorithm, however, encodes the information that describes this quantum state far more efficiently using an array of quantum switches, making the computation far more reasonable.

A substantial amount of the work on the algorithm was done at the California Institute of Technology, while Jordan was a postdoctoral fellow. His coauthors are fellow postdoc Keith S.M. Lee (now a postdoc at the University of Pittsburgh) and Caltech's John Preskill, the Richard P. Feynman Professor of Theoretical Physics.

The team used the principles of to prove their algorithm can sum up the effects of the interactions between colliding particles well enough to generate the sort of data that an accelerator would provide.

"What's nice about the simulation is that you can raise the complexity of the problem by increasing the energy of the particles and collisions, but the difficulty of solving the problem does not increase so fast that it becomes unmanageable," Preskill says. "It means a quantum computer could handle it feasibly."

Though their algorithm only addresses one specific type of collision, the team speculates that their work could be used to explore the entire theoretical foundation on which fundamental physics rests.

"We believe this work could apply to the entire standard model of physics," Jordan says. "It could allow quantum computers to serve as a sort of wind tunnel for testing ideas that often require accelerators today."

Explore further: Serious security: Device-Independent Quantum Key Distribution guards against the most general attacks

More information: S.P. Jordan, et al. Quantum Algorithms for Quantum Field Theories. Science, June 1, 2012, DOI 10.1126/science.1217069

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Tomba
5 / 5 (6) Jun 01, 2012
I was present at a lecture given by Feynman to a group of Hughes scientists in the early 80s. In this lecture he proposed using quantum physics to build a quantum computer to better understand fundamental physics. It felt like a remarkable lecture at the time (I don't know if it was the first lecture he gave on the topic) and many left with their minds somewhat blown. Maybe it's finally on the horizon. Feynman was at the tip of the arrow of physics.
Terriva
1.3 / 5 (4) Jun 01, 2012
The results of contemporary quantum computers are approximate due the quantum noise. For example the Groower's algorithm has been reproduced with 96% reliability. Von Neuman computer couldn't work with such level of noise at all.

For quantum computer working with reliability 96% like the 64-bit classical computer you will need to repeat the computation 109 times to achieve the result of the same level of precision. Such a precision could be achieved with parallelizing of results of 109 atoms in the role of qubits. We can realize fast, such level of parallelization of quantum bits is just achieved in classical transistors, which are constructed from 109 atoms each.

For me the quantum computers are just hype, the main reason of which is to provide the employment for researchers involved. But can they really beat the classical computers in computational power? IMO they cannot, because this power is limited with the same laws both for classical, both for quantum computers.
Tangent2
1.3 / 5 (4) Jun 01, 2012
But can they really beat the classical computers in computational power? IMO they cannot, because this power is limited with the same laws both for classical, both for quantum computers.


That's a joke, right? What about a quantum computer that uses entanglement?
Terriva
1 / 5 (3) Jun 01, 2012
Classical computers use entanglement as well. The extremely high precision of classical computers is based on entanglement of many electrons within their transistors.
A2G
1 / 5 (1) Jun 01, 2012
In the end you still have to do real world collisions. If QC approach was used instead of building the LHC the "computer" would have already found the Higgs because the current theories call for it to be there. But alas it has not been found.

Quantum or not computers will still follow the old garbage in, garbage out.

You have to do real world experiments at some point to make sure that your programming was accurate and your theories are correct.
antialias_physorg
1 / 5 (1) Jun 01, 2012
What about a quantum computer that uses entanglement?

What about it?
Computers work on information. Entanglement carries no information.

But comparing quantum computers to the regular kind is comparing apples and oranges. Both are good at entirely different things. So we'll probably see hybrid designs to get the best of both worlds.
vega12
not rated yet Jun 01, 2012
In the end you still have to do real world collisions. If QC approach was used instead of building the LHC the "computer" would have already found the Higgs because the current theories call for it to be there. But alas it has not been found.

Quantum or not computers will still follow the old garbage in, garbage out.

You have to do real world experiments at some point to make sure that your programming was accurate and your theories are correct.


Well, most recent results seem to lean toward presence of the Higgs boson. But that is not the main point: of course we will still need experiments. But even on the theory side, there are tons of things we don't know how to calculate efficiently, so being able to do such simulations efficiently is a good thing. It will make it easier to test our theories against experiment because for once we will be able to use the theory to make predictions.