Experimental quantum communication complexity

We prove that by communicating N-1 times a single qubit, instead of N-1 classical bits, the success probability for solving some N partner communication complexity tasks is strongly enhanced. The superiority, as measured by the quantum-to-classical fidelity ratio, of the quantum scheme grows exponentially with N. We report an experimental implementation of these tasks for N=5. Even without correcting for any inefficiencies of the state-of-the-art setup, our multiparty quantum protocol still outperforms the best classical protocols.