Scientists have shown that sunlight can be used to create quantum entanglement, a surprising advance that could eventually help make quantum technologies more energy efficient. Quantum entanglement is a strange phenomenon in which two particles become connected so strongly that their properties remain linked, even when they are separated. Reporting their results in the journal Optica, the researchers showed that sunlight could generate high-quality entanglement between pairs of photons, the tiny particles that make up light. Earlier research from the University of Ottawa team had already shown that incoherent light from an LED could generate entangled photons. Satellites might use sunlight already available in space to generate quantum encryption keys without carrying energy-hungry lasers.