Modeling Pauli measurements on graph states with nearest-neighbor classical communication

Abstract

We propose a communication-assisted local-hidden-variable model that yields the correct outcome for the measurement of any product of Pauli operators on an arbitrary graph state, i.e., that yields the correct global correlation among the individual measurements in the Pauli product. Within this model, communication is restricted to a single round of message passing between adjacent nodes of the graph. We show that any model sharing some general properties with our own is incapable, for at least some graph states, of reproducing the expected correlations among all subsets of the individual measurements. The ability to reproduce all such correlations is found to depend on both the communication distance and the symmetries of the communication protocol.

9 pages, 2 figures. Version 2 significantly revised. Now includes a site-invariant protocol for linear chains and a proof that no limited communication protocol can correctly predict all quantum correlations for rings