LondonIonizing radiation disrupts quantum chips despite error correction.
Particles hit the silicon substrate, spawning quasiparticles that break qubits even under active error correction.
The fix requires physical shielding or building processors underground — an architectural constraint that pushes back practical quantum-computing timelines.
Sources: Phys.org
THE SUBSTRATE PROBLEM
Superconducting qubits sit on a silicon chip cooled to roughly 10 millikelvin — colder than deep space. The chip itself is a target: any high-energy particle that strikes it dumps energy into the lattice that the cryostat cannot remove fast enough.
WHAT QUASIPARTICLES ARE
In a superconductor, electrons pair up (Cooper pairs) and flow without resistance. A particle strike breaks pairs into single electrons — quasiparticles — which tunnel into the qubit's Josephson junction and corrupt its state. One strike can flip dozens of qubits at once.
WHY ERROR CORRECTION FAILS HERE
Surface codes assume errors are independent and local — one qubit goes wrong, neighbors vote to fix it. A cosmic ray creates a correlated burst across a wide patch of the chip simultaneously. The voting collapses because too many neighbors are also wrong.
THE FLUX AT SEA LEVEL
At Earth's surface, roughly one muon per square centimeter strikes every minute, alongside background gamma rays from concrete, granite, and trace radioisotopes in the chip packaging itself. A 1 cm² processor is hit dozens of times per hour.
THE UNDERGROUND PRECEDENT
Particle physics solved this problem decades ago by going deep. Italy's Gran Sasso lab sits under 1.4 km of rock; Japan's Kamioka mine is under 1 km. Muon flux drops by a factor of a million. Quantum hardware is now eyeing the same playbook — Google and others have run test chips in mine shafts.
THE TIMELINE COST
Roadmaps to fault-tolerant quantum computing assumed error rates would fall with better gates and more qubits. Cosmic rays impose a floor that scaling alone cannot cross — meaning practical machines may need shielded vaults or underground siting, which adds years and capital to every deployment.