9 ms·
Energy 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, li
by philipswood 2y ago
Energy 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 agoWait, so does this imply (ignoring the time requirements) that you could do NP calculations with a feasible amount of energy, because the inputs and outputs are small? Combine that with something that uses time dilation to make it go fast (from our frame of reference) and you'd be giving even hypothetical quantum computers a silver medal.
- Dylan16807 2y agoIf you're going to use time dilation so you can wait for the computer to calculate, it's hard to imagine a setup where the power needs of the computer are more than a rounding error in comparison.
- AnthonyMouse 2y agoIf you're using time dilation the power needs of the computer (in terms of how much fuel you need) are proportional to the rate time passes inside. If the goal is to get the ratio way up there, the power consumption gets important. Especially if you're using the velocity-based method and have to accelerate the fuel.
- Dylan16807 2y agoYou'd be accelerating yourself, not the computer. If you launch the computer it just takes longer.
- Strilanc 2y agoNot unless you can isolate the computer from environmental noise exponentially well. Otherwise you'll need to spend exponential energy on entropy removal / error correction (e.g. keeping the dilution fridge running).
- canadianfella 2y ago[dead]
- 2y ago