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Comment by jerf | Hacker News Reader

"if you’re doing superconducting qubits, which is maybe the most popular approach today, then at a bare minimum, you need to cool everything down to 10 mKB,"

Anyone know what that temperature is supposed to be? Googling for "mkb" doesn't come up with anything I can scrounge up. mK for milli-Kelvin doesn't make much sense, as you don't need to get that low for superconductivity in general, and that's a pretty hard temperature to reach.

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10 milliKelvin is the temperature range that allows the usage of commercial RF equipment in the ~5GHz range to control the qubits.

The relationship between the two is essentially Energy = k_B * temp = h * freq, where k_B is the Boltzmann constant and h is Planck's constant.

If the temperature was higher than 10 milliKelvin, then thermal fluctuations could have comparable energy to your control signals and thus cause unintended electronic state transitions.

It's not just superconductivity that you need. You also need to reduce thermal noise to maintain coherence between qubits. mill-Kelvin is the typical temperature range D-Wave computers go to [1], for instance.

In fact, when you see large mainframe-like pictures of quantum computers, the big box mostly contains cooling equipment. The actual circuitry is pretty small.

[1] https://www.dwavesys.com/tutorials/background-reading-series...

Well, there's a pretty cool DJ with the username "mkb" across a few different sites. Aaronson is correctly noting that any superconducting quantum computer needs to be at least ten times as cool as that guy in order to work.

Yup, he meant 10 milliKelvin: https://www.scottaaronson.com/blog/?p=4121#comment-1804067

Thank you, and thank you to the other repliers who answered. I have learned something today.

I guess it may be mass times the Boltzmann constant (https://en.wikipedia.org/wiki/Boltzmann_constant) BUT I HAVE NO IDEA. And maybe he is handwaving some arithmetic manipulations. (?)

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