  In this letter, we report a realization of synchronization-free quantum
teleportation and narrowband three-photon entanglement through interfering
narrowband photon sources. Since both the single-photon and the entangled
photon pair utilized are completely autonomous, it removes the requirement of
high demanding synchronization technique in long-distance quantum communication
with pulsed spontaneous parametric down-conversion sources. The frequency
linewidth of the three-photon entanglement realized is on the order of several
MHz, which matches the requirement of atomic ensemble based quantum memories.
Such a narrowband multi-photon source will have applications in some advanced
quantum communication protocols and linear optical quantum computation.
