Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ucbvax.ARPA Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!rimey From: rimey@ucbmiro.ARPA (Ken Rimey) Newsgroups: net.physics Subject: Re: Smallest possible memory element Message-ID: <9045@ucbvax.ARPA> Date: Sat, 13-Jul-85 07:29:11 EDT Article-I.D.: ucbvax.9045 Posted: Sat Jul 13 07:29:11 1985 Date-Received: Sun, 14-Jul-85 08:26:43 EDT References: <350@sri-arpa.ARPA> <454@linus.UUCP> Sender: nobody@ucbvax.ARPA Reply-To: rimey@ucbmiro.UUCP (Ken rimey) Organization: U.C. Berkeley Lines: 22 >> Given the technology to do it, the smallest a computer memory >>could be made would probably be an electron, in that a spin in one >>direction would be a one and a spin in the other direction would be a >>zero. ... >> Eric > > there is a problem here. according to Heisenberg, reading a file >would irreversibly garble it. > > -phil You say that sensing the spin of an electron would garble it. I don't see why. Is your reference to Heisenberg a reference to the Heisenberg uncertainty principle? I don't see how it applies. It relates to pairs of simultaneously unknowable observables. For example, if you measure the momentum of a particle you disturb its position. This is simply because a state of well-defined momentum is a plane-wave, which clearly does not have a well-defined position. Excuse me if you already know this. Anyway, I don't see that this prevents you from non-destructively measuring whether a spin is up or down. Am I missing something? Ken Rimey