### Quantum preparation games

Mathematical Physics Seminar

27th November 2020, 2:00 pm – 3:00 pm

Online seminar, Zoom

A preparation game is a task whereby a player sequentially sends a number of quantum states to a referee, who probes each of them and announces the measurement result. The measurement setting in each round, as well as the final score of the game, are decided by the referee based on the past history of settings and measurement outcomes. Many experimental tasks in quantum information, such as entanglement quantification or magic state detection, can be cast as preparation games. In this talk, I will introduce general methods to design n-round preparation games, with tight bounds on the average game scores achievable by players subject to constraints on their preparation devices. These results will be illustrated by devising new adaptive measurement protocols for entanglement detection and quantification. Surprisingly, the standard procedure in entanglement detection, namely, estimating n times the average value of a given entanglement witness, is in general sub-optimal for detecting the entanglement of a specific quantum state. On the contrary, there exist n-round experimental scenarios where detecting the entanglement of a known state optimally requires adaptive measurement schemes.

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