  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. Here we settle
this question in the affirmative.
