Entangled Photon Source Ticks All Boxes

Quantum photonic technologies require sources that create entangled, indistinguishable pairs of photons on demand that can be extracted from the source at a high rate. Previous experiments have achieved each of these four criteria individually, or in some combination, but have fallen short of fulfilling them all. For example, the method of creating entangled pairs by splitting a single high-energy photon into two—so-called spontaneous parametric down-conversion—lacks the capability to generate such photons on demand. Now, Hui Wang at the University of Science and Technology of China and colleagues demonstrate a semiconductor quantum-dot photon emitter that simultaneously achieves all the requirements in a single device.