Loss-resistant state teleportation and entanglement swapping using a quantum-dot spin in an optical microcavity

We present schemes 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 achievable only 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 optical spin manipulation methods at single-photon levels, which could be used to preserve the spin coherence via spin echo techniques.