X-Message-Number: 15048 Date: Tue, 28 Nov 2000 20:49:25 -0800 From: Lee Corbin <> Subject: Quantum Mechanics vs. Uploading I have never believed that arguments about QM were at all relevant to uploading, any more than questions about the Many-Worlds interpretation are. Probably these were first invoked for illustration, or as part of a reductio-ad- absurdum. The two main concerns about uploading are (1) can a program imitate a human being satisfactorily? and (2) if it did, would it necessarily be conscious, or have feelings, or have an "inner life", etc? None of this has anything to do, in my opinion, with quantum mechanics. Robert Ettinger writes, >Now the uploaders have painted themselves into another corner. >When a computer describes or calculates the "quantum state" of >a physical system, my understanding is that this means it states >or calculates the value of each coordinate in the phase space >of the system, as precisely as the uncertainty principle or the >Bekenstein Bound allows. For a particle in a one-dimensional flat >well this means it specifies x and p (position and momentum) at >time t. x1 includes a short space interval, p1 includes a small >momentum dispersion, and t1 includes a short time interval. >The computer then goes on to calculate the "next" (t2) values >of x and p, etc. For all I know, if the goal for some crazy uploader was to actually calculate a _quantum state_ IN DETAIL, then perhaps you have shown this to be problematic. For as you write, >But this is not quantum reality! It is just selecting, out of the >infinite possibilities, the one "most probable" succeeding state. >For the computer to reflect quantum reality (as presently understood >by most physicists) or to reflect Many Worlds, it would have to >calculate ALL the possible successive "states" and would therefore >effectively grind to a halt immediately. To go around calculating quantum states is very ambitious! I'm real glad that for all the computer programs that I've been asked to write over the years, all they ever wanted was for the computer to do stuff. :-) Imagine that the year is 1927, and that a city is planning on replacing its venerable old cop who has been directing traffic at Broadway and Main for decades. Someone at the city council meeting says, "Look, it's simply impossible to have a mechanical instrument replace Officer O'Malley! Even if it were possible classically, the new wave mechanics shows that in order to calculate the next quantum state, e.g., "blow-whistle", the calculations must be done for at least 10^100 possible worlds!" So at the risk of being unfair and changing the grounds of the argument, let me proceed to the actual reality of what is wanted. First, by no means can a realistic program that replaces me do EXACTLY what I would have done in every case, because even I cannot do EXACTLY what I would have done if.... Robert Ettinger had not written a certain email! Or if the phone rings! Everything that happens throws me into an entirely new reality if anyone is foolish enough to be really picky about it. The mathematician E. Borel used to find it very interesting and significant to perform classical computations that show that displacing a gram of matter in the star Sirius by a mere centimeter will change the state of a liter of gas on Earth within a second (after the gravitational influence arrives eight years later, of course). Second, there is an incredibly broad range of successful "Lee Corbin imitation behavior" that a program might implement. I won't go into the very interesting and complex question, quite relevant to our own cryonic revivification scenarios, of how we know that we've got back the same person or not. But I will remark that even in the cases of severe brain surgery, we are able to tell, even though the patient's behavior is very greatly affected. Last, do programs really "calculate" their next state? We have possibly an abuse of language here. A program goes from one state to another every time it rearranges some data or loads some data from the outside. In the ultimate example, a TM writes a 1 or a 0, or moves and goes into a different "state" (i.e., technically into a "state" defined as an abstract quadruple or quintuple). Does a neuron calculate its next state when it fires or not? I don't think that we want to talk this way, and we probably don't want to say that an artificial neuron necessarily calculates anything either. I hope I'm not going out on a limb here, but what say we reserve "calculation" for an actual arithmetic computation? It's possible that unconscious associations of this term have led to some misapprehensions. >Note carefully that the Turing Machine ITSELF is CLASSICAL, even >though it can calculate quantum mechanics. > >So--once more--what do we have? The Turing Machine does not and >CANNOT emulate a person, because a real person does not always >evolve into the next most probable configuration. Sometimes his >next configuration is less probable. Therefore the emulation is >guaranteed to be different from what real life would be. (At >least "the" real life, as opposed to "a" real life.) As said before, "the" real life is a fiction anyway (since my phone may ring at any minute!) If it's the strict determinism that is true of a TM that's bothersome, then of course TM's can also simulate pseudo-random outcomes. But more importantly, the tape of an actual TM that was simulating a person would be as extraordinarily rich and unpredictable as our own world is. Its behavior would, in effect, be driven by vast numbers of random inputs---like someone trying to get its attention---just as ours is. Lee Corbin Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=15048