Method and apparatus for fault-tolerant quantum communication based on solid-state photon emitters

A system for generating entanglement between two solid-state single photon emitters comprising:

• a coherent light source;
• a plurality of nodes, each node comprising a single photon emitter with several levels, each with different probabilities for coherent scattering of the light source via state-selective elastic light scattering;
• and
• means for generating entanglement between optically-active qubits in a first node and a second node by interference of the scattered light at a beam splitter.

A method of quantum communication in a system comprising a plurality of nodes, comprising the steps of:

• generating entanglement between optically-active qubits in a first node and a second node adjacent said first node;
• mapping an optically-active qubit onto a memory qubit;
• leaving an optically-active qubit available to generate entanglement between unconnected nodes;
• projectively measuring from a third node adjacent said second node four Bell states in a manifold involving both the optically-active qubit and the memory qubit associated with an emitter at said second node;
• and
• using the outcomes of the measurements of the four Bell states to obtain a singlet state in a remaining pair of memory qubits and implementing a deterministic entanglement swap to produce a memory qubit entanglement between said second and third nodes approximately mirroring said optically-active qubit entanglement between said first and second nodes.