GIST Professor Byoung Seung Ham"s research team shows

that quantum advantage can be gained in classical information processing

The advent of quantum devices may forever change the world as they can theoretically perform certain tasks and computations (such as the factorization of large numbers) much more efficiently than other devices based on classical systems. However, to better understand the advantage quantum devices may have over traditional devices, many researchers utilize the mathematical branch known as game theory to determine if it is possible to replace the classical strategy with a quantum strategy to gain a quantum advantage.

Game theory, which is concerned with strategies employed by players and the payoff (or scores) of those strategies, has been applied to a diverse range of fields from evolutionary biology to economics to determine if different strategies (or actions) employed by the players produce better outcomes in the players" scores, especially when the game (or scenario) is repeated numerous times.

Traditionally, it has been thought that the rules for classical game theory games must be altered to give quantum strategies an advantage. However, Professor Byoung Seung Ham who is the director of the Gwangju Institute of Science and Technology (GIST) Center for Photon Information Processing led an international team of researchers to show that it is possible to gain a quantum advantage without making any quantum modification to a classical game.

The researchers did so by designing a new classical two-player game called the Secret-Bit Guessing Game where one player named Bob attempts to guess the secret bits of the other player, Alice. The researchers then mapped out two parallel strategies Bob can employ in choosing the best answer: one strategy uses classical probabilities and the other uses quantum. On the basis of the payoff-function analysis, the researchers show that quantum reasoning can be more advantageous without having to change or alter the classical properties of the game.

The researchers investigated whether or not a player in a classical game can gain a quantum advantage without having to change or alter the classical setting of the game, and the results indicate that it is possible to gain a quantum advantage even when all of the strategies are classical.

The research was entitled "Quantum-mechanical machinery for rational decision-making in classical guessing game" and authored by Jeongho Bang, Junghee Ryu, Marcin Pawłowski, Byoung S. Ham, and Jinhyoung Lee was published online by Scientific Reports on February 15, 2016. The research was supported by the Basic Science Research Program from the National Research Foundation of Korea that is funded by the Ministry of Science, ICT, and Future Planning.

First-author Dr. Jeongho Bang said, "This study is an important contribution to the field of quantum information research because it provides tremendous insight in how quantum advantage can be gained even when using classical information or classical data."