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: The research group in Japan sought to create a superconductor microprocessor that’s adiabatic, meaning that, in principle, energy is not gained or lost from t
by incompatible 2y ago
: The research group in Japan sought to create a superconductor microprocessor that’s adiabatic, meaning that, in principle, energy is not gained or lost from the system during the computing process.
I thought that there was a law of information theory that requires expending energy, I think it's Landauer's principle. It seems to be disputed though.
https://en.wikipedia.org/wiki/Landauer%27s_principle https://en.wikipedia.org/wiki/Landauer%27s_principle
- bryanlarsen 2y agoIf the superconducting microprocessor is 80x as efficient as a normal micro, that means that it uses about 100 million times as much energy as Landauer's principle. (A normal micro uses a billion times as much, and Landauer's energy is ~1/5th at superconducting temperature).
- incompatible 2y agoYes, but the quote suggests no energy transfer at all. All you need then is a cold place (somewhere in remote space perhaps, or after the heat death of the Universe) and your computation can continue forever without power. It doesn't seem intuitive that that would be possible.
- reaperman 2y agoIt is extremely likely that the quote is hyperbolic (wrong / inaccurate). If someone broke Landauers limit, that would be a massive headline in academia. Hell even reasonably approaching Landauer’s limit would be huge news. Most likely this headline is a confusion from how signal/power transmission (rather than calculation/work) is truly lossless in superconductors.
- jakobson14 2y agoContinue forever? no. Be performed once at no cost? maybe. I'm kinda sceptical that a computation to which the 2nd law is indifferent would occur spontaneously without immediately reversing. The 2nd law is what determines the direction that things typically progress.
- KiranRao0 2y agoPer the wikipedia article: “Modern computers use about a billion times as much energy per operation.” I’m guessing the efficiency gains can be considerable before hitting this limit.
- HPsquared 2y agoThat's actually fewer zeroes than I was expecting.
- Thorondor 2y agoLandauer's limit assumes that computation uses a thermodynamically irreversible process and erases bits of information. This is not necessarily true for all useful computers [0]. So theoretically speaking, it's not impossible to create an adiabatic microprocessor. Skepticism is definitely warranted though. [0] https://en.m.wikipedia.org/wiki/Reversible_computing https://en.m.wikipedia.org/wiki/Reversible_computing
- philipswood 2y agoEnergy is expended when you zero or set a bit. If you compute reversibly you need use special logic gates to not throw any bits away during the computation, like the Toffoli gate. All your operations need to have the same number of input and output bits and needs to be able to run forwards and backwards. Effectively you set or zero no bits during the entire computation that can't be losslessly reversed. If you structure your computation this way you can do it adiabatically. You still however need to expend energy when you set all the bits your program requires for execution when you start a computation.
- m463 2y agoI think maybe we need the idea of a "bit well" to match the "bit bucket". Then it would be possible to just borrow bits when we set bits.
- oceanplexian 2y agoMy analogy probably isn’t perfect but isn’t this how an abacus or a slide rule works? You expend energy to set the values for computation but the act of computing and then reading them expends no energy.
- bgnn 2y agoYeah this is a good analogy
- heavenlyblue 2y agoThat's a bad analogy because moving stuff in abacus is the computation itself.
- lupusreal 2y agoSuppose you put the abacus sideways, such that setting a bead requires working against gravity, but then returning the bead to the original position gives you that energy back?
- AnthonyMouse 2y ago