PERSPECTIVES T

he interaction between light and mat-ter at the quantum level offers intrigu-ing ways to process and transport information [see, for example, ( 1)]. Experi-mental realizations of quantum computers are, however, still in their infancy. A major challenge is the realization of a qubit—the quantum version of a bit that entangles quan-tum states—that can be manipulated and cou-pled to other qubits. For example, one strat-egy for coupling light and matter places an atom or quantum dot in a tiny cavity, where it couples resonantly with the cavity’s opti-cal modes ( 2). Practical diffi culties of this approach arise because a highly effi cient cav