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YouTube Comments - 454 Comments
Top Comments of this video!! :3
There actually is an area where the Josephson junction revolutionized electronics - the standards grade voltage reference. It used to be that voltage references were basically just special batteries. But once the Josephson junction came around, we realized we could use it to build a very, very accurate frequency to voltage converter. And since we have really, really good frequency references, we now have really, really good voltage references. In fact, the change was so dramatic, meteorologists actually changed the definition of the volt because of it. These days, Josephson junctions themselves aren't very common because they are big, expensive, and not very portable (tanks of liquid helium will do that), but virtually all modern electrical test equipment, especially production test equipment, can literally trace its calibration back to one of them. And that's not just a one off thing. Electrical test equipment is required to undergo periodic recalibration to stay in spec. The equipment that does that has a documented, periodically updated calibration train back to a national standards lab, ultimately culminating in a Josephson junction array.
99 |
"At the risk of being made an idiot later, I am saying that I donât believe that any superconductor-based computer will become commercially competitive at any time in the future."
We'll see if your quote ages better than Lord Kelvin's quote: "I think it cannot be done. No balloon and no aeroplane will ever be practically successful."
183 |
Still waiting for my cold fusion powered graphene magic carpet...
135 |
Capacitive and Inductive âlossesâ arenât losses as such. Theyâre just energy storage. The magnetic fields created in a superconductor donât dissipate anything. They are just energy stored in the wire, and trying to stop the current will release it. That being said, high frequency current through a superconducting wire will still emit EM radiation to the environment. Good circuit design should mitigate this, but I donât believe it can be eliminated altogether. To summarize: there should be losses, but only as radiation â which is a few orders of magnitude less than what the inductance and capacitance values would imply otherwise.
93 |
In fact, in high speed circuitry, the shape of the data lines and the material around them is far more important than its own material.
160 |
For quantum photonics, it would have made an impact. Superconducting nanowire single photon detectors are bulky because of the cooling and everyone would love to integrate them on-chip.
17 |
Lk99 claims to work by using tunneling supercurrents between quantum wells not cooper pairs so the working temperature calculations might be different
214 |
Thank you for doing all of the math on the temperatures I was lost until you got to Wedgewoodđ. As always your videos and research are great stuff.
65 |
No surprise there. LK-99 study was released without consent of all of the authors, had no peer review, didn't measure resistance and hasn't been replicated. It was always going to be a long shot.
Microscopic uses will be hard with any superconductor. So think of big applications instead?
I can't speak to feasibility, but I am interested to see if rail guns and mass drivers might find some benefit from high temperature superconductors.
Cheers!
68 |
Even way back with vacuum tube circuits we had to deal with Miller Capacitance that could limit both frequency and gain factor. That's what Pentode tubes were invented to improve upon, the extra elements at different voltage potentials lower the Miller Effect and allow better control of the electrons flowing inside the tube. The new Pentode tubes worked at a lot higher frequencies compared to the original triodes, and they could be built to control larger currents.
23 |
12:59 đ. Yeah, there are those many units of temperatures. For those curious, Rankine is the equivalent of Kelvin in imperial units
11 |
Back when I was working on Thin Film HTSC there was talk of using them for interconnects. Our current densities for TBCCO were in the 10 E6 A/cm^ range if I remember correctly. We were at 3" wafers when I left. We never made one, but we did mount a SUN microsystems processor on a closed cycle Stirling Gooler. This sped up the chip significantly, but the whold thing wasn't really practical. We also made an HTSC SQUID with HTSC Josephsen Junctions.
39 |
Very cool! Especially enjoyed the bit of history on IBMs research on Superconducting computers based on Josephson junctions. Interestingly the same tech is now the basis of qubits in IBMs Quantum computers. Wonder what they are thinking about LK99...
31 |
Surprised that you missed the most important use of the Josephson Junction, and that is as a voltage standard. Gone are day the days of Watson cells. In fact, that could make for an interesting video (if you haven't looked into it already), the history of standards of measurement and the quest to move them from being based on artifacts to mathematics.
10 |
12:59 I'm disappointed with the glaring omission of the RÊaumur and Rømer scales. Personally, I only use temperature scales containing only the consonants r-m-r in my daily life.
6 |
Informative thank you ! The current density limit of cuprate discuted at 6:00 has to be the reason why new MIT SPARC Tokamak Toroidal magnets have such a huge thickness. Add this to what we learned from your first video (cuprates are ceramics less convenient than metallic Nb-Ti superconductor) and one can realize that current HTS are not the industrial and economical revolution some are pretending.
5 |
My first thought when reading about LK99 was that if it worked, it could be used to create tiny MRI machines and super powerful and small electromagnets for all kinds of research and industry use. The reason MRIs are huge is because of the cooling requirements to keep the superconducting magnets at operating temperature. The reason most powerful electromagnets are huge is because of heat generation.
Sad it hasn't panned out. But we may still see a room temperature superconductor material as computing power increases and AI can be used to explore options faster.
30 |
Thanks Jon, for another very informative video. Your content just keeps getting better.
3 |
It would be great to have another Ice Age to cool down our hot transistors
10 |
@gz7006
9 months ago
Well Mr. John Asianometry, I'll have you know I was promised laser weapons, heatless batteries and a woman to finally look in my direction by people who equate anything above a bronze age technological level to magic, so I must say that yes, it would've changed a lot of things.
1K |