  Quantum coherence could be sustained up to interstellar distances. It is
shown that the photon mean free path in certain regions of the electromagnetic
spectrum, such as within the radio or x-ray ranges, could allow sustaining of
the quantum state of a photon up to galactic distances. Therefore processes
involving quantum entanglement, such as quantum teleportation, could be
realized over very long distances in the Milky Way or other galaxies. This is
of fundamental interest and offers a new direction in the role of quantum
mechanics. Some limited applications of this observation are discussed.
