NO-CLONING THEOREM OF ENTANGLED STATES

We derive a necessary and sufficient condition for two pure states, ea ch entangled in two remote systems, to be clonable by the sequential a ccess to the two systems. The result shows to what extent the correlat ion to other systems can be read out from a subsystem without altering its marginal density operators. This extends the standard no-cloning theorem to the case of a subsystem correlated to others.