5 ms·

To be clear, despite the appearance of 'quantum' in the title, this is a development toward faster classical computers by using superconducting circuit elements

To be clear, despite the appearance of 'quantum' in the title, this is a development toward faster classical computers by using superconducting circuit elements (Josephson junctions). A computer using this type of logic would need to be cryo-cooled down to ~single-digit Kelvin temperatures, but as discussed in a thread a few weeks ago[0], a superconducting computer can still beat a conventional computer in terms of ops/Watt, even when the power consumption of the cooling equipment is included. [0] - https://news.ycombinator.com/item?id=25765128 https://news.ycombinator.com/item?id=25765128

HPsquared 6y ago
Very cool!
- wiz21c 6y ago
  Cool as cold ?
  - deleted 6y ago
    [deleted]
mdip 6y ago
Thanks for summing that up; based on the title, alone, I was considering clicking because I so rarely encounter a sentence such as this: containing so many words I know/use regularly yet when put together in that precise manner, appeared to be as to have been assembled by a garbage disposal.
contravariant 6y ago
Theoretically keeping something at the same temperature is at most going to double the energy requirements, though there's likely to be some additional practical issues with maintaining such a low temperature.
- amluto 6y ago
  Not even close. A perfect refrigerator will use vastly more than 1J to remove 1J from a 4.2K device. Look up Carnot’s theorem.
  - a1369209993 6y ago
    > A perfect refrigerator will use vastly more than 1J to remove 1J from a 4.2K device. While your actual point is true, your example is too loosely specified - the energy used by a perfect (or even imperfect) refrigerator depends on the temperature of the environment it's dumping the heat into. In the extreme (and also engineering-wise preferred) case, with a heat sink at cosmic microwave background temperatures of ~2.7K, a perfect refrigerator (rather, heat exchanger) would actually gain energy. (Of course, since the literally-glowing-hot sun takes up some portion of the sky, actually getting a <4.2K environment would likely require siting your computer in the Oort Cloud, if not outside the galaxy entirely, hence why your actual point is true.)
    - deleted 6y ago
      [deleted]
    - amluto 6y ago
      Touché. If you want to go down that road, I believe you’ll find that the maximum amount of heat that any machine can exhaust into the CMB (or, more generally, radiatively transfer into a medium at an effective temperature T_h) is precisely the amount of heat it would emit as a blackbody at T_h. IOW sending entropy into space requires generating a uniformly distributed random distribution of something and sending it into space and, if you want to use light, you end up with delta S = Q / T, where T is the temperature of the light. So your device will need a silly surface area, in addition to needing to be very well shielded from the sun. Now maybe you can cheat because, at the wavelengths in question, the effective surface area of an antenna is quite large, but I doubt this buys you much. But in some moral sense, you are entirely correct. If you put your computer on a cold moon with no view of the sun, you can sink quite a lot of heat at a low temperature. (A really good spectrally and directionally selective filter means you may not need to be quite as far from the sun as the Oort Cloud. Even just pointing an IR thermometer into a clear night sky gives a nice low temperature.)
blacksmith_tb 6y ago
Free cooling to those temperatures is available in orbit... well, free once you get there...
- deepsun 6y ago
  Nope, satellites on orbit have thermal protection from the sun's radiation. It's also harder to dump excessive temperature without matter around. IIRC space suits expel some finite amount of gas to get rid of extra heat.
  - deleted 6y ago
    [deleted]
  - blacksmith_tb 6y ago
    Ah, good point, that cooling only works when you're in the shadow of the Earth. I guess we'll have to keep sticking our datacenters in the ocean and at the poles.
KirillPanov 6y ago
> superconducting computer can still beat a conventional computer in terms of ops/Watt, even when the power consumption of the cooling equipment is included But likely not when the energy cost of manufacturing the cryocooler (which has a limited working life) is included. If you count dollars instead of joules the answer is a definite "no". The manufacturing cost per joule of the cryocooler, amortized over its usable life, far exceeds the value of the energy saved.
- semi-extrinsic 6y ago
  Well, if liquid hydrogen becomes a significant energy carrier, as many serious heavy engineering companies are currently working to realize, you might end up having "free" cooling capacity at ~25 K widely available, at least for data centres and such.

HPsquared 6y ago

Very cool!

wiz21c 6y ago
Cool as cold ?
- deleted 6y ago
  [deleted]

mdip 6y ago

Thanks for summing that up; based on the title, alone, I was considering clicking because I so rarely encounter a sentence such as this: containing so many words I know/use regularly yet when put together in that precise manner, appeared to be as to have been assembled by a garbage disposal.

contravariant 6y ago

Theoretically keeping something at the same temperature is at most going to double the energy requirements, though there's likely to be some additional practical issues with maintaining such a low temperature.

amluto 6y ago
Not even close. A perfect refrigerator will use vastly more than 1J to remove 1J from a 4.2K device. Look up Carnot’s theorem.
- a1369209993 6y ago
  > A perfect refrigerator will use vastly more than 1J to remove 1J from a 4.2K device. While your actual point is true, your example is too loosely specified - the energy used by a perfect (or even imperfect) refrigerator depends on the temperature of the environment it's dumping the heat into. In the extreme (and also engineering-wise preferred) case, with a heat sink at cosmic microwave background temperatures of ~2.7K, a perfect refrigerator (rather, heat exchanger) would actually gain energy. (Of course, since the literally-glowing-hot sun takes up some portion of the sky, actually getting a <4.2K environment would likely require siting your computer in the Oort Cloud, if not outside the galaxy entirely, hence why your actual point is true.)
  - deleted 6y ago
    [deleted]
  - amluto 6y ago
    Touché. If you want to go down that road, I believe you’ll find that the maximum amount of heat that any machine can exhaust into the CMB (or, more generally, radiatively transfer into a medium at an effective temperature T_h) is precisely the amount of heat it would emit as a blackbody at T_h. IOW sending entropy into space requires generating a uniformly distributed random distribution of something and sending it into space and, if you want to use light, you end up with delta S = Q / T, where T is the temperature of the light. So your device will need a silly surface area, in addition to needing to be very well shielded from the sun. Now maybe you can cheat because, at the wavelengths in question, the effective surface area of an antenna is quite large, but I doubt this buys you much. But in some moral sense, you are entirely correct. If you put your computer on a cold moon with no view of the sun, you can sink quite a lot of heat at a low temperature. (A really good spectrally and directionally selective filter means you may not need to be quite as far from the sun as the Oort Cloud. Even just pointing an IR thermometer into a clear night sky gives a nice low temperature.)

blacksmith_tb 6y ago

Free cooling to those temperatures is available in orbit... well, free once you get there...

deepsun 6y ago
Nope, satellites on orbit have thermal protection from the sun's radiation. It's also harder to dump excessive temperature without matter around. IIRC space suits expel some finite amount of gas to get rid of extra heat.
- deleted 6y ago
  [deleted]
- blacksmith_tb 6y ago
  Ah, good point, that cooling only works when you're in the shadow of the Earth. I guess we'll have to keep sticking our datacenters in the ocean and at the poles.

KirillPanov 6y ago

> superconducting computer can still beat a conventional computer in terms of ops/Watt, even when the power consumption of the cooling equipment is included But likely not when the energy cost of manufacturing the cryocooler (which has a limited working life) is included. If you count dollars instead of joules the answer is a definite "no". The manufacturing cost per joule of the cryocooler, amortized over its usable life, far exceeds the value of the energy saved.

semi-extrinsic 6y ago
Well, if liquid hydrogen becomes a significant energy carrier, as many serious heavy engineering companies are currently working to realize, you might end up having "free" cooling capacity at ~25 K widely available, at least for data centres and such.