Separable States Can Be Used To Distribute Entanglement
Toby S. Cubitt, Frank Verstraete, Wolfgang Dür, J. I. Cirac · Physical Review Letters · 2003
We show that no entanglement is necessary to distribute entanglement; that is, two distant particles can be entangled by sending a third particle that is never entangled with the other two. Similarly, two particles can become entangled by continuous interaction with a highly mixed mediating particle that never itself becomes entangled. We also consider analogous properties of completely positive maps, in which the composition of two separable maps can create entanglement.