Rebuilding A $700k Refrigerator

When cleaning out basements, garages, or storage units we often come across things long forgotten. Old clothes, toys, maybe a piece of exercise equipment, or even an old piece of furniture. [Ben] and [Hugh] were in a similar situation cleaning out an unused lab at the University of California Santa Barbara and happened upon an old refrigerator. This wasn’t just a mini fridge left over from a college dorm, though. This is a dilution refrigerator which is capable of cooling things down to near absolute zero, and these scientists are trying to get it to its former working state.

The pair are hoping to restore the equipment to perform dark matter experiments, but the refrigerator hasn’t been in use since about 2016 (and doesn’t have an instruction manual), which is a long time for a piece of specialty scientific equipment to be collecting dust. The first step is to remove wiring and clean it of all the grime it’s accumulated in the last decade. After that, the pair work to reassemble the layers of insulation around the main cooling plate and then hook up a vacuum pump to the device which also needed some repair work.

The critical step at this point is to evacuate the refrigerant lines so they can be filled with expensive Helium-3 and Helium-4. The problem is that there’s still some of this valuable gas in the lines that needs to be recovered, but the risk is that if any air gets into the cold section of the refrigerator it will freeze and clog the whole system. After chasing some other electrical and vacuum gremlins and discovering a manual from a similar refrigerator, they eventually get it up and running and ready for new scientific experiments. While most of us won’t discover a fridge like this cleaning out our attics, this refrigerator powered by rubber bands is a little more accessible to the rest of us.

20 thoughts on “Rebuilding A $700k Refrigerator

    1. The dilution refrigerator is just to get cold, which allows for exploring all sorts of interesting physics in addition to quantum computing! For superconducting quantum computers, dilution refrigerators are used to cool superconducting circuits to near absolute zero, so that the materials superconduct and thermal fluctuations don’t destroy the delicate quantum states encoding the quantum information. Superconducting quantum computers store information in the quantized energy state of a nonlinear resonator, so as a rule of thumb, kT has to be much less than Planck’s constant times the frequency of the resonator. Other quantum computing platforms, like trapped ions or Rydberg atoms, have a very different form factor — the atoms encoding the quantum information live in a vacuum chamber surrounded by a bunch of lasers, optics, and cameras to control and read out the quantum state.

    1. The unit as they got it would be around $700K to replicate. At around 3:53 in the first video, [Ben] explains that the refrigerator itself is around $500K new, but the wiring would add around another $200K.

  1. It does indeed look a lot like the quantum thing in: EEVblog 1594 – Inside a Quantum Computer! with Andrea Morello and that is to be expected. From what I understand you can “store” / create up to 3 qubits in a single atom, so the “quantum” part of a quantum computer is not going to be very big. The reason I mention it is because it has some nice details about the working of such a fridge.

  2. That’s John’s fridge. We had good documentation on our internal wiki page on how to run it, including how to operate the valve panel for the helium and nitrogen trap. John, or one of the former grad students across the way at Google, might still have those guides or a copy of the wiki pages.

  3. Heh. I was at UCSB, building a zero-g/pork cycle dilution refrigerator in the Lubin lab… At the turn on the century. Even older than the one I worked on, but at least I didn’t have to see any of my hackery on display.

  4. So, if it was used for a quantum computer, if i put a beer inside (thogh it doesn’t seems to have enough space for it) when it will become lost (is it bith quantified and inquantifable aka you know there’s a beer in the fridge, but you don’t know where – it happeneds in normal refrigerators, the fuller they are)?

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