Quantum logic at a distance

Quantum computers could revolutionize how specific computational problems are solved that remain untractable even for the world’s best supercomputers. However, although the basic elements of a quantum computer—realizing a register of qubits that
preserve superposition states, controlling and reading out qubits individually, and performing quantum gates between them—have been scaled to a few dozen qubits, millions are needed to attack problems such as integer factorization. One approach for scaling
up quantum computers is to “divide and conquer”—keep individual processing units smaller and connect many of them together. This approach leaves local processing nodes tractable but requires generation of entanglement and performance of quantum gates on qubits located at distant nodes to keep the advantages of quantum processing. On page 614 of this issue, Daiss et al. (1) made substantial progress toward this goal by performing quantum-logic operations on two distant qubits in an elementary network.