Ring photons and quantum entangled states, illustration. Micrometre-scale, ring-shaped resonator with a geometry engineered by researchers to produce pairs of entangled photons (particles of light) that have different wavelengths. Light from a pump laser (purple) generates one photon in each pair at a visible-light wavelength (red). The other photon has a wavelength in the telecommunications (near-infrared) part of the spectrum (blue). In quantum communication, this is an ideal pairing for an optical circuit: The visible light is used in quantum computing, while the telecommunications wavelength propagates through an optical fibre network. This research was carried out by scientists from the National Institute of Standards and Technology (NIST) and the University of Maryland NanoCenter. Image published in 2019.