# Link between quantum physics and game theory found

(Phys.org) —A deep link between two seemingly unconnected areas of modern science has been discovered by researchers from the Universities of Bristol and Geneva.

While research tends to become very specialized and entire communities of scientists can work on specific topics with only a little overlap between them, physicist Dr Nicolas Brunner and mathematician Professor Noah Linden worked together to uncover a deep and unexpected connection between their two fields of expertise: game theory and quantum physics.

Dr Brunner said: "Once in a while, connections are established between topics which seem, on the face of it, to have nothing in common. Such new links have potential to trigger significant progress and open entirely new avenues for research."

Game theory—which is used today in a wide range of areas such as economics, social sciences, biology and philosophy—gives a mathematical framework for describing a situation of conflict or cooperation between intelligent rational players. The central goal is to predict the outcome of the process. In the early 1950s, John Nash showed that the strategies adopted by the players form an equilibrium point (so-called Nash equilibrium) for which none of the players has any incentive to change strategy.

Quantum mechanics, the theory describing the physics of small objects such as particles and atoms, predicts a vast range of astonishing and often strikingly counter-intuitive phenomena, such as quantum nonlocality. In the 1960s, John Stewart Bell demonstrated that the predictions of quantum mechanics are incompatible with the principle of locality, that is, the fact that an object can be influenced directly only by its immediate surroundings and not by distant events. In particular, when remote observers perform measurements on a pair of entangled quantum particles, such as photons, the results of these measurements are highly correlated. In fact, these correlations are so strong that they cannot be explained by any physical theory respecting the principle of locality. Hence quantum mechanics is a nonlocal theory, and the fact that Nature is nonlocal has been confirmed in numerous experiments.

In a paper published in *Nature Communications*, Dr Brunner and Professor Linden showed that the two above subjects are in fact deeply connected with the same concepts appearing in both fields. For instance, the physical notion of locality appears naturally in games where players adopt a classical strategy. In fact the principle of locality sets a fundamental limit to the performance achievable by classical players (that is, bound by the rules of classical physics).

Next, by bringing quantum mechanics into the game, the researchers showed that players who can use quantum resources, such as entangled quantum particles, can outperform classical players. That is, quantum players achieve better performance than any classical player ever could.

Dr Brunner said: "Such an advantage could, for instance, be useful in auctions which are well described by the type of games that we considered. Therefore, our work not only opens a bridge between two remote scientific communities, but also opens novel possible applications for quantum technologies."

**More information:**Paper: 'Connection between Bell nonlocality and Bayesian game theory' by Nicolas Brunner and Noah Linden in

*Nature Communications*. www.nature.com/ncomms/2013/130 … full/ncomms3057.html

**Citation**: Link between quantum physics and game theory found (2013, July 12) retrieved 23 August 2019 from https://phys.org/news/2013-07-link-quantum-physics-game-theory.html

## User comments

Tektrixclay_fergusonhemititeantialias_physorgThey mean that by not being confined to locality (e.g. via entangled entities) the individual agent can react to information from a larger region, and thereby make a more informed (read: better) choice.

vacuum-mechanicsOkay, but quantum mechanics is still being 'physics' it is not a magic!

This seems like a magic, anyway even in the real world of magic there is 'physics' behind! Maybe there is a misinterpretation. Here is an interpretation based on 'physics' which is understandable…

http://www.vacuum...17〈=en

antialias_physorgJust because you don't understand it doesn't make it 'magic'.

To quote Arthur C. Clarke:

And QM seems to be sufficiently out of your league.

Science does not have to conform to what you think is 'common sense'. Common sense is something that developed through evolution based on observations of macroscopic environments. QM deals with microscopic environments.

Hence, why would you even expect your 'common sense' to map to that to any great degree?

Shoehorning observable/measurable facts into a 'vaccuum mechanics theory' that doesn't explain them and is internally inconsistent doesn't help.

dan42dayvisionablerObviously, any applications of quantum theory to game theory that were discovered by researchers are real game changers, and giving them away for free might not make sense. (Two puns included).

UrgeltIf this is just about showing a gaming advantage of non-locality - possessing better information than those who are relying on merely local information - I don't see what the fuss is about.

dedereuOur real world with quantummechanics is quite more powerful than the classical world that seems valid at the macroscopic level, with only one world amount the many parallel separated world appearing at each micro time, which is the only way to explain, without adhoc unproven hypothesis, why at the microscopic level it is possible to be delocalized at many place at the same moment and after decoherence at the macroscopic level, this possibility disappears, being at only one place and not working and on holiday at the same time.

ValeriaTValeriaTQB similarly says that the probabilities as to the outcome of the same experiment may not be the same for two different observers, as for example one observer may've conducted a previous experiment which alters their knowledge of the system. As each probability distribution is associated with a quantum state, this makes the quantum state subjective too. It may seem like solipsism, but a proponent of QB would argue that quantum theory is an observer centric - which from a subjectivist Bayesian POV could be interpreted as the strength of belief of the observer.

kochevnikjulianpenrodValeriaTShah Khanjon clokeGame Theory works mathematically because it is pre-designed to do so in the mistaken assumptions it makes, rather than because it establishes any fundamental characteristics of human behaviour. It is beloved of orthodox economist for the same reason, that it permits post hoc rationalizations of capitalism, i.e. capitalism exists therefore let us assume that it is both logical and functional (through equilibrium-based modelling, rational preference assumptions, etc.).

Odd to see a physics blog making this kind of fundamental mistake!

HiggsbengalibosonThose who are good chess player might understand that game theory gives the same pleasure as playing a game of chess against powerful computer.

But quantum theory...In world's of Feynman "bizarre".

JSCCMethinks this is your problem with game theory [excepting obvious inexperience], and that it has nothing to do with 'an empirically unproven theory based on debatable pre-suppositions made by mathematicians'. If that was the case, it wouldn't be capable of mathematizing natural selection. It is and has. This can then be translated into non-evolutionary game theory notation and provide equivalent results involving "conflict and cooperation between intelligent rational decision-makers".

So please drop the human behavior anti-intellectualism and be honest: you just don't like the possible implications, which is entirely unscientific because that's different than the method itself.

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