2) while a general bulk high current superconductor is limited in currentcarrying capacity this way, most of the time one is not interested in sending current one way, but also completing the circuit and getting current back the opposite way. Why can they not make power distribution cables with indefinite currentcarrying capacity the following way: consider a "multilayer" coaxial cable where the conductors are superconductors, and to prevent a magnetic field from arising the layers have alternating current directions, so that in any layer the net magnetic field is below the critical magnetic flux? (this would only be for power distribution, since this can't be used to build stronger superconductive electromagnets). The total current would be the sum of all the even, or of all the odd coaxial layers (the 2 sums are identical since they complete a circuit...) in essence co-locate the 2 problematic magnetic fields such that they cancel... A superconductive "humbucker"
This  is worth a few listens.
The colder you run a superconductor, the more current it can conduct.
T quoted for superconductivity is the phase transition for I = 0 A
e: looks like you got your answer haha
[2 with follow-up presentation]: https://snf.ieeecsc.org/abstracts/stp475-ampacity-project-%E...
That doesn't mean that it is not useful to conduct these experiments. They could give further insights into how superconductivity comes to be - or maybe discover a superconducting material that requires high (but not too high * ) pressures to form but remains stable when they are lowered back to normal pressure similar to how diamonds are stable at normal pressures but are require high pressure to be formed.
* Pressures only reachable by using diamond anvils would be highly impractical to produce any useful amount of material ;)
OK, it's a cart and horse affair as it is the resistance that causes the heat, but I'm mindful how lab work pans out into real-work. But even reducing resisting a bit in a practical, consumer useful way has massive benefits.
> OK, it's a cart and horse affair as it is the resistance that causes the heat,
Most of the heat comes from semiconductor conduction, leakage, and switching. Superconductors don't fix that. Not to mention, a major factor in resistance is diffractive losses is the ohmic layer surrounding transistors. The ohmic layer is necessary because direct metal-semiconductor connections create blocking diodes. The width of those wires at the connection points is so small that electrons could barely squeeze through. That was the reason we switched to "high-K" dielectrics, which have higher classical resistance but lower electron scattering. Superconductors have similar problems with entry and exit into superconducting areas.
Those voltages represent binary values. Usually a positive voltage is designated as a binary "1" and a zero voltage as a binary "0". Putting a "1" into a register (or whatever) is easy - just add the appropriate voltage. But how do you change that "1" into a "0"?
You do so by "grounding" the circuit - that is, a circuit is made where the voltage level representing the "1" is connected to the reference voltage level that represents "0". Since that voltage level is "0 volts" (usually - but not always - but it is usually lower than the voltage level representing "1"); that change in voltage happens to occur across a conductor, and that conductor has some resistance, and that ultimately is what generates the heat.
ASIDE: It is possible to reverse all of this - that is, use a negative or zero voltage to represent a "1" and a positive voltage to represent a "0", and so on - I'm not sure, though, that this is done in common practice, but I am certain it has been done somewhere at least once.
So - what does that mean? Well - it means that in a CPU, just by the fact that it is manipulating voltages that represent the binary symbols "1" and "0" - it is going to end up generating some amount of heat. The fasting these changes occur, the more heat that is output. The larger the voltages involved, the more heat is output (note how this explains why, as CPUs have gotten faster, their operating voltages have become lower).
How do you combat this? Well - it ain't easy - but what if you could, instead of grounding a voltage representing a "1" to make it a "0" - you instead used it elsewhere (in some manner) to generate a "1". That is, instead of wasting that voltage and energy as heat due to resistance, you used it instead to perform the opposite function elsewhere in the CPU?
Well - you can - though it ain't easy from what I understand. It's called:
> How do you combat this? Well - it ain't easy - but what if you could, instead of grounding a voltage representing a "1" to make it a "0" - you instead used it elsewhere (in some manner) to generate a "1". That is, instead of wasting that voltage and energy as heat due to resistance, you used it instead to perform the opposite function elsewhere in the CPU?
That's different and wouldn't really apply to a concept like resistance. It also doesn't need to be the opposite function, just... something.
that leans towards reversible computation, which would need a reversible computer (getting close to unitary transformations in QM)
But superconductivity is also a quantum phenomenon so it probably defies intuition.