Quantum networks advance with entanglement of photons, solid-state qubits: "The new result builds upon earlier work by Lukin's group to use single atom impurities in diamonds as qubits. Lukin and colleagues have previously shown that these impurities can be controlled by focusing laser light on a diamond lattice flaw where nitrogen replaces an atom of carbon. That previous work showed that the so-called spin degrees of freedom of these impurities make excellent quantum memory.
Lukin and his co-authors now say that these impurities are also remarkable because, when excited with a sequence of finely tuned microwave and laser pulses, they can emit photons one at a time, such that photons are entangled with quantum memory. Such a stream of single photons can be used for secure transmission of information."