Constant communication complexity protocols for multiparty accumulative boolean functions

Abstract

Generalizing a boolean function from Cleve and Buhrman \cite{cb:sqec}, we consider the class of {\it accumulative boolean functions} of the form $f_B(X_1,X_2,..., X_m)=\bigoplus_{i=1}^n t_B(x_i^1x_i^2... x_i^m)$, where $X_j=(x^j_1,x^j_2,..., x^j_n), 1\leq j\leq m$ and $t_B(x_i^1x_i^2... x_i^m)=1$ for input $m$-tuples $x_i^1x_i^2...x_i^m\in B\subseteq A\subseteq \{0,1\}^n$, and 0, if $x_i^1x_i^2...x_i^m\in A\setminus B$. Here the set $A$ is the input {\it promise} set for function $f_B$. The input vectors $X_j, 1\leq j\leq m$ are given to the $m\geq 3$ parties respectively, who communicate cbits in a distributed environment so that one of them (say Alice) comes up with the value of the function. We algebraically characterize entanglement assisted LOCC protocols requiring only $m-1$ cbits of communication for such multipartite boolean functions $f_B$, for certain sets $B\subseteq \{0,1\}^n$, for $m\geq 3$ parties under appropriate uniform parity promise restrictions on input $m$-tuples $x_i^1x_i^2...x_i^m, 1\leq i\leq n$. We also show that these functions can be computed using $2m-3$ cbits in a purely classical deterministic setup. In contrast, for certain $m$-party accumulative boolean functions ($m\geq 2$), we characterize promise sets of mixed parity for input $m$-tuples so that $m-1$ cbits of communication suffice in computing the functions in the absence of any a priori quantum entanglement. We compactly represent all these protocols and the corresponding input promise restrictions using uniform group theoretic and hamming distance characterizations.