Giordano Scappucci

On a silicon chip that resembles a neighborhood, qubits, electrons with spin, live in separate 'houses.' Previously, neighbors could only chat over the fence, but now a road has been laid between them: along it, a qubit can ride to any of the four stops. The road is a bus that carries the electron without losing its quantum state.

A silicon chip the size of a fingernail holds billions of tiny switches. But a quantum computer needs not switches but individual electrons trapped in microscopic pits. These pits are quantum dots. And here's the catch: two neighboring pits that look identical can hold an electron differently. One is slightly deeper, the other slightly shallower.

A bridge where pedestrians and cyclists flow together without getting in each other's way. That's roughly how hybrid systems of superconductors and semiconductors work: the former carry current without loss, the latter control that current.

Imagine a ladder whose rungs are tiny magnets. If neighboring magnets point in opposite directions, the ladder is "calm." But if you make them all point the same way, the whole structure becomes magnetized and "stubborn." Scientists built such a ladder from germanium atoms — a semiconductor used to make transistors.