Dartmouth Events

Abstract: Information needs to be encoded in physical systems to be exchanged (communication) and  manipulated (computation). As such, computation and communication undergo the limitations imposed by the laws of physics. For instance, when communication is restricted to a) limited resources (i.e. a single information carrier) and b) finite speed of propagation (bounded by the speed of light), classical physics imposes a fundamental limit. Quantum systems, however, can violate this limitation. I will show that communication bounded to the exchange of a single quantum particle in superposition of different spatial locations can result in “two-way signalling”, a task that is impossible in classical physics. Starting from an easy bipartite ‘quantum game’, I then generalize the protocol to an arbitrary number of parties and show that while classically the probability of success is asymptotically decreasing as the number of parties grows, quantum superposition enables the players to accomplish the task always with certainty.
Moreover, I will report on the recent experimental demonstration of these proposed theoretical findings, and on the practical applications for cryptography.