Cryostat Wiring Bottleneck

Scaling a superconducting quantum computer means scaling a dilution refrigerator's plumbing along with it: every qubit needs several physical coax lines running from room temperature down to a chip sitting at ~10 millikelvin, and every one of those lines is a thermal short between stages. This simulator models a real five-stage cryostat — 50 K, 4 K, still, cold plate and mixing chamber — computing the conductive heat load each stage's wiring dumps into it against that stage's real cooling-power budget. Push the qubit count and coax-line-per-qubit sliders far enough and the mixing chamber's heat load overtakes its budget, its equilibrium temperature climbs, thermal-photon occupation in the qubits' readout resonators rises with it, and the chip visibly decoheres — the actual scaling wall every quantum-computing lab's cryogenic infrastructure runs into.