Researchers at the University of Illinois at Urbana-Champaign have constructed a quantum-mechanical state in which the colors of three photons are entangled with each other. The state is a special combination, called a W state, that retains some entanglement even if one of the three photons is lost, which makes it useful for quantum communication. Such entangled states also enable novel quantum applications and tests of fundamental physics.
Source:
https://phys.org/news/2019-09-three-photon-color-entangled-state.html