Entangling atoms by persistent poking In quantum mechanics, repeated measurements targeting a particular unoccupied state of the system can keep that state from being occupied. Barontini et al. used this so-called quantum Zeno effect to restrict the dynamics of an ensemble of 36 ⁸⁷ Rb atoms acting as qubits and residing in an optical cavity. The measurement of the cavity transmission blocked off the collective state in which all qubits were in their ground state. The ensuing dynamics resulted in the entanglement of the atoms, creating a potential resource for quantum information processing. Science , this issue p. 1317