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Quantum problems solved through games

Nature volume 532, pages 184185 (14 April 2016) | Download Citation

  • A Correction to this article was published on 27 April 2016

This article has been updated

Humans are better than computers at performing certain tasks because of their intuition and superior visual processing. Video games are now being used to channel these abilities to solve problems in quantum physics. See Letter p.210

In March, the mobile-game developer Supercell released a video thanking the 100 million people around the world who play its games daily1. According to estimates, by the age of 21 the average US citizen has spent more than 10,000 hours playing video games2 — the equivalent of working in a full-time job of 40 hours per week for five years. So is it possible to channel the enormous amount of human brainpower used in this way by designing games that have a purpose? More specifically, can video games be developed in which people solve computationally intractable research problems as a side effect of playing? Writing on page 210 of this issue, Sørensen et al.3 answer this question with a resounding 'yes'. They have developed video games that help to solve a problem relating to the realization of a new, efficient and scalable architecture for a quantum computer.

Despite their capacity to handle vast amounts of data, there are many problems in science that computers cannot yet solve. It is therefore highly desirable to harness innate human abilities to perform tasks that are beyond the grasp of current machines. The challenge is how to turn a research problem into a game, a process known as gamification.

Such a game should not only have a structure that embeds the specific research problem — with rules and winning conditions that encourage exploration of the 'landscape' of solutions — but also be fun to play. Successful examples include citizen-science games such as Foldit (ref. 4), EteRNA (ref. 5) and EyeWire (ref. 6), which are used to study protein folding, RNA folding and neuron mapping, respectively. Their success stems from humans' intuition and superior understanding of the 'real' world.

In this context, Sørensen and colleagues' work is an amazing feat, because quantum mechanics is the most counterintuitive and bizarre of all physical theories. Quantum particles behave in several unusual ways. They can be in several locations at the same time, can tunnel through potential-energy barriers, and can correlate with each other in such a way that their individual identity is lost. Niels Bohr's quote, “Anyone who is not shocked by quantum theory has not understood it”, is as relevant now as it was when quantum physics was first developed some 100 years ago.

The authors developed a video game called Quantum Moves (ref. 7) in an effort to solve one of their own practical problems. They are working on a prototype of a quantum computer based on atoms trapped in an artificial crystal of light8— periodic potential-energy wells generated by lasers. Quantum logic-gate operations can be performed in this system by moving atoms using a highly focused laser beam (an optical tweezer)9.

But quantum-computing operations must be executed fast — faster than the time taken for the quantum state of a system to lose its quantum properties10. This is where the real difficulty arises: how can the optimal quantum move be found in the shortest possible time? Moreover, for perfect fidelity of gate operations, there is a fundamental limit to the minimum duration of each operation, known as the quantum speed limit. Numerical approaches have failed to accurately predict the quantum speed limit for the class of time-dependent problems tackled by Quantum Moves.

One of the challenges of Quantum Moves is called BringHomeWater. In this challenge, players have to move an optical tweezer to a region where an atom is trapped in a simplified version of the artificial light crystal. They then have to collect the atom and move it to a target area as fast as they can — simulating one of the basic steps needed to operate a logic gate or perform a quantum simulation in the authors' prototype quantum computer. The atom is visualized as a quantum-mechanical wavefunction, which looks like water in a glass (Fig. 1). The faster the atom is moved, the easier it is to 'spill' the water. The players thus have to find the fastest way to bring home the atom without losing it (spilling the water) along the way, providing information that helps the researchers to optimize atom movements in the quantum computer.

Figure 1: The online game BringHomeWater.
Figure 1

a, This snapshot shows a still image of BringHomeWater, part of a game developed by Sørensen and colleagues3. b, In the game, players move an optical tweezer (represented by the left-hand curve; the black symbol is a cursor used to move the tweezer) from the home region towards an atom (depicted as a light-green liquid) in a potential-energy well (the right-hand curve). The players must find a route that brings the liquid home as quickly as possible, without spilling it. Sørensen et al. used the fastest moves found by players to optimize the transfer of atoms within their quantum computer; such optimization is required for quantum-logic operations. Large arrows show tweezer movements.

Sørensen et al. show that move-optimization schemes that use the players' solutions outperform the best known strategies devised by computers, and provide new lower bounds to the quantum speed limit. The players have thus identified the 'settings' needed for the optimal implementation of simple quantum-logic operations. Not only that, their solutions also helped the researchers to understand the physical mechanisms by which such strategies work in the weird quantum world.

So how can game players solve difficult research problems in quantum theory when they have no knowledge of either the puzzling phenomena of quantum physics or the sophisticated mathematical formalism used to describe it? One can do things in games that cannot be done in reality, so gamers are used to experimenting with possibilities that go beyond the classical laws of physics. Perhaps this ability to think outside the box allows them to make the creative leap necessary to tackle quantum problems.

Understanding the principles and key conditions for the successful gamification of quantum problems is an interdisciplinary endeavour requiring the interaction and collaboration of quantum physicists, game researchers, neuroscientists and many others. Whether Sørensen and colleagues' method will be applicable to a wide range of problems in quantum physics is currently an open question. But because we are on the verge of a new era of quantum technologies, this approach is definitely worth pursuing, and is a theme of initiatives such as Quantum Game Jam11.

Notes

Change history

  • 18 April 2016

    Reference 7 in the reference list was incorrect. This has now been corrected.

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  1. Sabrina Maniscalco is at the Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, Turku 20014, Finland.

    • Sabrina Maniscalco

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Correspondence to Sabrina Maniscalco.

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