biep@cs.vu.nl (J. A. "Biep" Durieux) (06/01/87)
As far as I understand there are three different issues to the problems of QM interpretations. As I hardly know what I am talking about, please correct me wherever I am wrong (but please note that I introduce QM bit by bit, so don't react to the beginning of the article saying there is more to it if that more is mentioned below). 1) Objects seem to be "spread out" in space, according to their wave function. The physical reality of this phenomenon is shown by letting a particle interfere with itself (e.g. the two-hole experiment). Whether this be true or not, I suppose nobody has any serious philosophical problems with it being true (barring the complexity theory problems of the collapsing). Certain actions force the particle to collapse, one of them being sensing the particle. 2) It is not possible to calculate or measure certain properties of a particle precisely (e.g. the product of location and impulse), since due to the discreteness of energy transfer, the particle is too heavily shaken by the act of measuring. In this rendering, again I suppose nobody will have serious problems with it. Another rendering, however, poses that those properties don't exist except as far as they are measured. There is a means of deciding between the two, and that is by means of Bell's equalities. So I might build a Bells box, which, If a particle entered, would tell me whether the particle were or were not in a superposition of states. But, if that were true, I could build a FTL communication device, the Bibaphone :-) thanks to Aspect! See the figure for details. A constant ----------------------------------------------------------------------- ----- ----- ----- | B | - -<- - - -<- - - - | A | - - - ->- - - ->- - | C | ----- ----- ----- | ^ ^ V | | A = Aspect box, turns an incoming particle into two parts; B = Bell box, decides whether such a part is in a superposition of states or not C = Controller, looks at a particle part if it receives a signal. Figure: Working scheme of the Bibaphone. ------------------------------------------------------------------------ stream of particles is coming in in an Aspect box. From this box, particle parts (PP's) are being sent into two directions, to very distant devices: at one end a controller box, which can selectively either let a PP pass without disturbing it, or inspect a PP in order to find its spin; at the other end a Bell's box, which finds out (probably with statistical methods, but that just means we need to send a whole bunch of particles at the same time) whether the PP it receives are in a superposition of spin states or just in a single (possibly unknown) one, i.e. whether there are or are not any hidden variables describing the spin state. Now whenever the controller receives a signal, it inspects the PP's which pass through it, thereby forcing them in a single spin state, thereby forcing their companion PP's in a single state, thereby triggering the whistle of the Bell's box. Voila, FTL information transfer. I can see just one problem: there was something with Bell's equations needing multiple properties, an inspection possibly can inspect only one property. Is this a real problem? Is this *the* problem (i.e. exactly the reason why the Bibaphone wouldn't work)? OK, back to our survey: So, I don't know yet what to think of the proposed non-existence of hidden variables. Did Bell take into account that a particle might be smeared out in space, or did it just suppose it had one location? 3) The most difficult problem (and the one I have not yet seen defended to some degree) is the supposed observer-dependency of the state of a particle. It is said that the first state of uncertainty came up when the first life appeared in the universe. Is there any experiment showing that an observer (as opposed to an interference with a light beam, or a photo- graphic sheet) is needed to reach some effect? Is there any experiment which depends on someone looking or not looking at a volt meter? If so, please describe; of not, what is meant by stating that the experiment depends on the observer? Well, that's a lot of rambling for someone who doesn't know what he is talking about. -- Biep. (biep@cs.vu.nl via mcvax) Never confound "power", "command" with "right", especially not when it concerns our own body!