  We analyze a novel method that uses fixed, minimal physical resources to
achieve generation and nested purification of quantum entanglement for quantum
communication over arbitrarily long distances, and discuss its implementation
using realistic photon emitters and photonic channels. In this method, we use
single photon emitters with two internal degrees of freedom formed by an
electron spin and a nuclear spin to build intermediate nodes in a quantum
channel. State-selective fluorescence is used for probabilistic entanglement
generation between electron spins in adjacent nodes. We analyze in detail
several approaches which are applicable to realistic, homogeneously broadened
single photon emitters. Furthermore, the coupled electron and nuclear spins can
be used to efficiently implement entanglement swapping and purification. We
show that these techniques can be combined to generate high-fidelity
entanglement over arbitrarily long distances. We present a specific protocol
that functions in polynomial time and tolerates percent-level errors in
entanglement fidelity and local operations. The scheme has the lowest
requirements on physical resources of any current scheme for fully
fault-tolerant quantum repeaters.
