3 ms·

I was on a workshop once where the topic was entropy and somehow we got into a discussion regarding Maxwell's Damon... This strongly reminds me of that discussi

I was on a workshop once where the topic was entropy and somehow we got into a discussion regarding Maxwell's Damon... This strongly reminds me of that discussion. The problem for the Damon is, that it needs to change the state of the trap according to the state of the incoming particle. And if you just hand wave "such a decision making thing exists", then you have your contradiction. But we tried, for several days, to come up with _any_ implementation (including fantasy materials) that could conceivably exist _and_ produce that effect. And for each and every attempt to build one, we came up _immediately_ with diffusive parts, where energy _must_ be lost. We concluded, that while non of us would feel confident to _rule out_ a possible existence of Maxwell's Damon, we wouldn't _at all_ be surprised if it could be ruled out. So while you are entirely correct, with enough hand-waviness, you can build reversible computations. But I have yet to see an argument, where a _potential_ implementation of one is argued to the end.

mjburgess 4y ago
It's sufficient for my purposes just to show that "bit" in a logical model and "bit" under some idealised thermodynamic thought experiment are radically different notions. Reality, i am sure, has many systems which are settable and measurable and changeable at some minimum energy... and which can interface with devices of interest. For any given problem, the limit case energy requirement is defined by the needs of the algorithm. If we require setting a highly complex input state, and if we require interactions with certain devices, then we've immediately ruled out a great deal. These systems would provide you with a certain kind of "limit-case correspondence" between "logical bits" and "ideal physical bits" --- but we dont know what this system is. You dont get it from just playing around with units, nor these kinds of thought experiments. You need to know what algorithm you're talking about, and what it's requirements are. If the algorithm is understood just to be "the whole of reality" and if we suppose that it is fundamentally just aggregates of discrete states being flipped (to me, highly unlikely).... then the energy requirements are Everything... which sum, i imagine (via energy conservation), to zero.

mjburgess 4y ago

It's sufficient for my purposes just to show that "bit" in a logical model and "bit" under some idealised thermodynamic thought experiment are radically different notions. Reality, i am sure, has many systems which are settable and measurable and changeable at some minimum energy... and which can interface with devices of interest. For any given problem, the limit case energy requirement is defined by the needs of the algorithm. If we require setting a highly complex input state, and if we require interactions with certain devices, then we've immediately ruled out a great deal. These systems would provide you with a certain kind of "limit-case correspondence" between "logical bits" and "ideal physical bits" --- but we dont know what this system is. You dont get it from just playing around with units, nor these kinds of thought experiments. You need to know what algorithm you're talking about, and what it's requirements are. If the algorithm is understood just to be "the whole of reality" and if we suppose that it is fundamentally just aggregates of discrete states being flipped (to me, highly unlikely).... then the energy requirements are Everything... which sum, i imagine (via energy conservation), to zero.