We show how shared entanglement, together with classical communication and
local quantum operations, can be used to perform an arbitrary collective qu
antum operation upon N spatially-separated qubits. A simple teleportation-b
ased protocol for achieving this, which requires 2(N - 1) ebits of shared,
bipartite entanglement and 4(N - 1) classical bits, is proposed. In terms o
f the total required entanglement, this protocol is shown to be optimal for
even N in both the asymptotic Limit and for 'one-shot' applications. (C) 2
000 Published by Elsevier Science B.V.