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Quantum Physics, quant-ph
Abstract:
The distribution of entanglement between macroscopically separated parties
represents a crucial protocol for future quantum information networks.
Surprisingly, it has been theoretically shown that two distant systems can be
entangled by sending a third mediating system that is not entangled with either
of them. Such a possibility seems to contradict the intuition that to
distribute entanglement, the transmitted system always needs to be entangled
with the sender. Here, we experimentally distribute entanglement by exchanging
a subsystem and successfully prove that this subsystem is not entangled with
either of the two parties. Our implementation relies on the preparation of a
specific three-mode Gaussian state containing thermal noise that demolishes the
entanglement in two of the three bipartite splittings. After transmission of a
separable mode this noise can be removed by quantum interference. Our work
demonstrates an unexpected variant of entanglement distribution and improves
the understanding necessary to engineer multipartite quantum information
networks.
