  We present a scheme for efficient state teleportation and entanglement
swapping using a single quantum-dot spin in an optical microcavity based on
giant circular birefringence. State teleportation or entanglement swapping is
heralded by the sequential detection of two photons, and is finished after the
spin measurement. The spin-cavity unit works as a complete Bell-state analyzer
with a built-in spin memory allowing loss-resistant repeater operation. This
device can work in both the weak coupling and the strong coupling regime, but
high efficiencies and high fidelities are only achievable when the side leakage
and cavity loss is low. We assess the feasibility of this device, and show it
can be implemented with current technology. We also propose a spin manipulation
method using single photons, which could be used to preserve the spin coherence
via spin echo techniques.
