When an electron and a positron meet, they briefly form a tiny atom — positronium. Its annihilation gives birth to two photons in a strange state: like two coins that always land on opposite sides. Scientists have figured out how to verify this quantum entanglement by 'pushing' photons against electrons — and this might open the door to new technologies.
🎯 Positronium is the lightest exotic 'atomic' system: it is 920 times lighter than hydrogen and decays in 0.1 nanoseconds.