  We report the observation of entanglement between a single trapped atom and a
single photon at remote locations. The degree of coherence of the entangled
atom-photon pair is verified via appropriate local correlation measurements,
after communicating the photon via an optical fiber link of 300 m length. In
addition we measured the temporal evolution of the atomic density matrix after
projecting the atom via a state measurement of the photon onto several well
defined spin states. We find that the state of the single atom dephases on a
timescale of 150 $\mu$s, which represents an important step toward
long-distance quantum networking with individual neutral atoms.
