Davide Degli Esposti

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.