A quantum prediction from 1931 just came to life

Nearly a century after physicist Hans Bethe predicted them, scientists have created and directly observed unusual quantum states known as “Bethe strings” in an ultracold gas. By cooling cesium atoms to near absolute zero and trapping them in thousands of tiny one-dimensional tubes, researchers were able to make groups of atoms bind together without ordinary chemical bonds. These strange clusters could contain six or more particles and even collide with one another without falling apart.