Momentum-Entangled Helium Atoms Demonstrate Quantum Link in Motion
Physicists cooled helium to near absolute zero to form a Bose-Einstein condensate, split it with lasers to produce entangled atom pairs, and used a Rarity-Tapster interferometer with single-atom momentum detection to demonstrate Bell-like correlations in the motion of two massive helium atoms—the first time entanglement has been shown in the momentum of moving mass. The result, a long-sought confirmation of textbook quantum mechanics, hints at future ultra-precise quantum sensors and tests of quantum gravity, with plans to explore momentum–mass entanglement by colliding helium-3 and helium-4 isotopes.