Reversible Computation Models at least do not consume energy, according to physical laws, since no information is erased. And there are also Fredkin Gate and Toffoli Gate which can effective simulate classical irreversible computation circuits. So why don't chips switch to reversible models to save energy consumption? Is it the problem of "noise" that occurs in computation? What kind of "noise" then?

  • $\begingroup$ This does not look like a theoretical computer science question. Your question is about computer hardware, it might be suitable for Electrical Engineering. Please read the FAQ to understand the scope of cstheory. $\endgroup$ – Kaveh Feb 2 '12 at 23:51

there is a lot of interest however it appears there are some early prototypes but overall not commercial chips so far. see eg Reversible computing is ‘the only way’ to survive Intel's heat mentioning michael frank at UF, his page here RevComp - The Reversible and Quantum Computing Research Group.

from what I can tell it looks like the reversible designs probably require larger chip area to compute the same problems and current designers would rather pay for mainly minimizing chip area at the expense of "heat". and designers have gotten very adept at minimizing heat in nonreversible designs.

one area of new innovation are energy capturing designs that can capture waste heat and convert it back into electricity. eg see Phononic Devices’s Chips Convert Waste Heat into Electricity

the industry is moving toward capturing waste heat for useful purpose eg building heating esp with supercomputers.

of course quantum computation is the "holy grail" for reversible designs but its proving very difficult to create systems due to the issue you mention in qm circuits-- noise or the so called "decoherence problem". the only commercial system so far seems to be dwave which is very expensive & niche right now.

  • $\begingroup$ Thank you. How can chips capture heat to convert it into electricity? Doesn't it conflict with the second law of thermodynamics? $\endgroup$ – Strin Feb 2 '12 at 7:41
  • $\begingroup$ think, similar principles to solar cells which convert radiant energy into electricity. also you asked about "noise". the main noise in conventional circuits comes from smaller gate widths and indeed [thermal/near-quantum] noise is becoming a problem in shrinking gate widths smaller than say ~30nm or so. $\endgroup$ – vzn Feb 2 '12 at 15:48

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