Nowadays it seems that the word quantum is being applied to almost everything. One sees books on the "Quantum Brain" or the "Quantum Leadership" or "Quantum Healing." Now, the most recent area to come under the quantum influence is game theory. Here however, quantum game theory (QGT) is a very real and serious area of scientific research. As the name implies, it involves the application of principles of quantum mechanics to game theory. Quantum game theory has received attention in the past but the topic was treated only theoretically. Only recently have researchers begun to experimentally address the field, as reported in Nature [445(7124), 144-146].

The beginnings of quantum game theory stretch back to around 1999, when mathematician David Meyer of the University of California, San Diego published a paper on the subject. His paper dealt with a comparison between quantum and classical strategies, and showed that a quantum strategy will always win against a classical one in a game between two players who take turns flipping a coin. The basic idea is that quantum mechanics allows the coin to be both heads-up and tails-up at the same time, so the person with the classical strategy will be outplayed every single time. Yet the field of quantum game theory did not take off quickly, partly due to the fact that quantum information itself was still a very incomplete field. The main problem is that scientists are many decades away from getting a quantum computer to physically work. Add to that the issue that game theory has problem of is own, which most glaring of all is the fact that predictions of game theory are often directly opposite to what really happens in reality.

But researchers at HP Labs in Palo Alto, California are making new strides in addressing these problems. Led by economist Kay-Yut Chen and physicists Ted Hogg and Raymond Beausoleil, the group has been at the forefront of quantum game theory research. In a paper they published a few years ago, they calculated that in the quantum version of the famous prisoners' dilemna, players would cooperate 50% of the time. In an effort to test this prediction, the Hewlett-Packard scientists randomly selected about a dozen students from Stanford University to participate in a version of the prisoners' dilemna. In this case, each student was given $100 and the choice to keep it or contribute it to a common fund. The students themselves had no idea that quantum mechanics had anything to do with their game. Surprisingly, it turns out that the quantum prediction was correct – the students cooperated about 50% of the time.

Despite the recent successes of the HP team, they still have a long way to go. One advantage they do have is the fact that fewer qubits are needed in quantum games compared to those in other areas of quantum information theory. Currently, they are working on developing new and better quantum algorithms to calculate scenarios in which the numbers of players in a game is significantly large. One of the grand hopes of Hewlett-Packard is that the work of their scientists will be applied to a new business model for selling digital content such as movies and music on the internet. Quantum game theory may still be a nascent field, but it appears to be a promising one.

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