Improved Quantum Communication Complexity Bounds for Disjointness and Equality

  • Authors:
  • Peter Høyer;Ronald de Wolf

  • Affiliations:
  • -;-

  • Venue:
  • STACS '02 Proceedings of the 19th Annual Symposium on Theoretical Aspects of Computer Science
  • Year:
  • 2002

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Abstract

We prove new bounds on the quantum communication complexity of the disjointness and equality problems. For the case of exact and non-deterministic protocols we show that these complexities are all equal to n+1, the previous best lower bound being n/2. We show this by improving a general bound for non-deterministic protocols of deWolf. We also give an O(驴n驴clog* n)-qubit bounded-error protocol for disjointness, modifying and improving the earlier O(驴n log n) protocol of Buhrman, Cleve, and Wigderson, and prove an 驴(驴n) lower bound for a class of protocols that includes the BCW-protocol as well as our new protocol.