The coldest room in the solar system
Nadir is a dilution refrigerator in low Earth orbit. Its lowest stage holds at seven millikelvin — colder than the space it flies through, and stiller than any room we know how to build on the ground.
Gravity was never the problem
A machine like this one on Earth sits on two floors of poured concrete and still hears the road outside. Pulse tubes hammer at 1.4 Hz. Helium lines shake. Every one of those vibrations arrives at the qubit as heat.
In orbit there is nothing to isolate from. The shield radiates straight into a 2.7 K sky, so the first three stages cost almost nothing to hold — and the compressor that would have shaken the frame never gets switched on.
Six plates, each one colder
The gold is not ornament. Every plate is oxygen-free copper, gold-plated so it does not tarnish and so it keeps radiating heat upward to the stage above it. Nothing here is machined for looks — it is machined for contact.
- 300 KVacuum can. Room temperature, station side.
- 50 KRadiation shield. Rejects everything the sun puts on the hull.
- 4 KStill plate. Where the helium mixture starts to separate.
- 800 mKHeat exchangers. 288 coaxial lines, attenuated in stages.
- 100 mKCold plate. Magnetic shielding closes around the package.
- 7 mKMixing chamber. The processor hangs from it, and nothing touches it.
Inside the glass, nothing moves
Four hundred and twelve superconducting qubits on a single sapphire die, wired out through niobium-titanium above 800 mK because copper would carry heat down the line faster than the mixture can pull it back.
Coherence at 7 mK runs past 900 microseconds. On the ground the same die reads 340. The difference is not better physics. It is a quieter room.
Book the cold
Access is sold as exclusive windows, not shared queues. You get the whole machine, calibrated the hour before you start, for as long as the window runs.