Over the past decade, researchers have become good at creating devices that emit single photons on demand, which is a key ingredient for quantum computing. However, reliably producing exactly two photons at the same time has remained a challenge.
Now, researchers in China have developed a device that behaves almost like a miniature photon-pair factory. In experiments, 98.3 percent of the emitted light from this device appeared as photon pairs, one of the purest results ever achieved with a solid-state device.
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