  Quantum communication holds promise for unconditionally secure transmission
of secret messages and faithful transfer of unknown quantum states. Photons
appear to be the medium of choice for quantum communication. Owing to photon
losses, robust quantum communication over long lossy channels requires quantum
repeaters. It is widely believed that a necessary and highly demanding
requirement for quantum repeaters is the existence of matter quantum memories
at the repeater nodes. Here we show that such a requirement is, in fact,
unnecessary by introducing the concept of all photonic quantum repeaters based
on flying qubits. As an example of the realization of this concept, we present
a protocol based on photonic cluster state machine guns and a loss-tolerant
measurement equipped with local high-speed active feedforwards. We show that,
with such an all photonic quantum repeater, the communication efficiency still
scales polynomially with the channel distance. Our result paves a new route
toward quantum repeaters with efficient single-photon sources rather than
matter quantum memories.
