Laura d'Avossa

Quantum computing promises a revolution, but its real power will only unfold in a network. The best “brains” — superconducting qubits — communicate at microwave frequencies. The ideal “couriers” — optical photons — fly at hundreds of terahertz. A direct hookup is impossible.

Inside a cryostat cooled to tens of millikelvins live superconducting qubits. There aren't many of them: tens, at most hundreds. Crosstalk and thermal noise prevent packing more. But cracking RSA-2048 requires anywhere from ten thousand to ten million physical qubits.