disjointness;
quantum communication complexity;
quantum information complexity;
CONDITIONAL MUTUAL INFORMATION;
DIRECT-PRODUCT THEOREMS;
ONE-WAY COMMUNICATION;
EXPONENTIAL SEPARATION;
D O I:
10.1137/16M1061400
中图分类号:
TP301 [理论、方法];
学科分类号:
081202 ;
摘要:
We prove a near optimal round-communication tradeoff for the two-party quantum communication complexity of disjointness. For protocols with r rounds, we prove a lower bound of (Omega) over tilde (n/r + r) on the communication required for computing disjointness of input size n, which is optimal up to logarithmic factors. The previous best lower bound was Omega(n/r(2) + r) due to Jain, Radhakrishnan and Sen [Proceedings of FOGS, 2003, pp. 220-229]. Along the way, we develop several tools for quantum information complexity, one of which is a lower bound for quantum information complexity in terms of the generalized discrepancy method. As a corollary, we get that the quantum communication complexity of any Boolean function f is at most 2(O(QIC(f))), where QIC(f) is the prior-free quantum information complexity of f (with error 1/3).