  Quantum repeaters are nodes in a quantum communication network that allow
reliable transmission of entanglement over large distances. It was recently
shown that highly entangled photons in so-called graph states can be used for
all-photonic quantum repeaters, which require substantially fewer resources
compared to atomic-memory based repeaters. However, standard approaches to
building multi-photon entangled states through pairwise probabilistic
entanglement generation severely limit the size of the state that can be
created. Here, we present a protocol for the deterministic generation of large
photonic repeater states using quantum emitters such as semiconductor quantum
dots and defect centers in solids. We show that arbitrarily large repeater
states can be generated using only two coupled emitters, reducing the necessary
number of photon sources by six orders of magnitude. Our protocol includes a
built-in redundancy which makes it resilient to photon loss.
