### Quantum one-way communication can be exponentially stronger than classical communication

Regev, O *(Tel Aviv)*

Tuesday 29 March 2011, 10:00-11:00

Seminar Room 1, Newton Institute

#### Abstract

In STOC 1999, Raz presented a (partial) function for which there is a quantum protocol communicating only O(log n) qubits, but for which any classical (randomized, bounded-error) protocol requires poly(n) bits of communication. That quantum protocol requires two rounds of communication. Ever since Raz's paper it was open whether the same exponential separation can be achieved with a quantum protocol that uses only one round of communication. In other words, can quantum one-way communication be exponentially stronger than classical two-way communication? Here we settle this question in the affirmative.

Based on joint work with Bo'az Klartag.

NOTE: This talk is about lower bounds for *classical* communication complexity; no knowledge of quantum communication complexity is assumed or required.

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