SCIENCE SPIN-OFFS

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Two-way communication with a single quantum particle

Flavio Del Santo, Borivoje Dakic
(Submitted on 25 Jun 2017 (v1), last revised 20 Feb 2018 (this version, v3))

In this letter we show that communication when restricted to a single information carrier (i.e. single particle) and finite speed of propagation is fundamentally limited for classical systems. On the other hand, quantum systems can surpass this limitation. We show that communication bounded to the exchange of a single quantum particle (in superposition of different spatial locations) can result in "two-way signaling" which is impossible in classical physics. We quantify the discrepancy between classical and quantum scenarios by the probability of winning a game played by distant players. We generalize our result to an arbitrary number of parties and we show that the probability of success is asymptotically decreasing to zero as the number of parties grows, for all classical strategies. In contrast, quantum strategy allows players to win the game with certainty.

https://arxiv.org/abs/1706.08144