Re: Question on quantum computing and many-worlds interpretations of Quantum Mechanics

Ooops - - sorry, didn't mean to ping the whole list. Hopefully none of you
work for direct mail marketers.

On 3/3/06, David Opderbeck <dopderbeck@gmail.com> wrote:
>
> Hey George -- just saw this. I'd like a copy. 20 Smith Lane, Midland
> Park, NJ 07432
>
>
> On 3/2/06, George Murphy <gmurphy@raex.com> wrote:
> >
> > I've noted this before here but I'll be happy to send a copy of the
> > paper I
> > gave at the 1987 ASA meeting, "Parallel Worlds, Quantum Theory, and
> > Divine
> > Sovereignty" to anyone who wants it & gives me a snailmail address.
> >
> > Shalom
> > George
> > http://web.raex.com/~gmurphy/
> > ----- Original Message -----
> > From: "Loren Haarsma" < lhaarsma@calvin.edu>
> > To: "_American Sci Affil" <asa@calvin.edu>
> > Sent: Thursday, March 02, 2006 8:40 PM
> > Subject: Re: Question on quantum computing and many-worlds
> > interpretations
> > of Quantum Mechanics
> >
> >
> > >
> > >
> > > I agree that there might be theological issues to worry about in a
> > > many-worlds interpretation of quantum mechanics.
> > >
> > > But I want to focus just on a scientific issue.
> > >
> > > Someone might have told you:
> > >
> > >> The success of a quantum device therefore
> > >> necessitates the existence of parallel universes ( multiverses ) in
> > order
> > >> for all the computations to be carried out in parallel.
> > >
> > > But that is false.
> > > Absolutely, positively, false.
> > > A successful quantum computer will not in any way necessitate the
> > > existence of parallel universes or the Everett "many worlds"
> > > interpretation of quantum mechanics.
> > > I'd stake my Ph.D. in atomic physics on it.
> > >
> > >
> > > There are many different interpretations of quantum mechanics. Four
> > > general categories are (1) standard "Copenhagen" interpretations; (2)
> > > Everett-type "many worlds" interpretations; (3) "non-local"
> > > hidden-variable interpretations; (4) "local" hidden variable
> > > interpretations (i.e. hidden variable interpretations which don't
> > allow
> > > changes in the wave function to propagate faster than the speed of
> > light).
> > > The "Bell Inequality" is a famous theoretical prediction which
> > describes
> > > and experiment in which "local hidden variable" interpretations make a
> >
> > > different prediction for the outcome of an experiment than the other
> > three
> > > interpretations. The experiment has been done, and local hidden
> > variable
> > > interpretations have been shown to be inconsistent with data.
> > >
> > > There is, as of now, NO experimental or theoretical observational way
> > to
> > > distinguish between the other three interpretations (Copenhagen
> > > interpretations, many-worlds interpretations, and non-local
> > > hidden-variable interpretations). All three classes of
> > interpretations
> > > make identical predictions for how quantum computers should work.
> > >
> > >
> > > Quantum computers work by utilizing cleverly designed Hamiltonians in
> >
> > > _this_ universe, not by using anything from other universes. (In
> > > classical or in quantum mechanics, a Hamiltonian is an equation or a
> > > functional operator which describes the energy of the system in terms
> > of
> > > variables such as position, momentum, angular momentum, etc.)
> > >
> > >
> > > Here's an analogy. A few decades ago, people built some
> > sophisticated
> > > "analog computers" by combining resistors, capacitors, inductors, and
> > > transitors in clever circuits. Analog computers are not as versitile
> > as
> > > digital computers. They cannot solve _any_ sort of mathematical
> > problem
> > > the way digitical computers can. But there there are certain classes
> > of
> > > problems (e.g. second-order differential equations) which analog
> > computers
> > > can solve much more quickly than digital computers. The electrons in
> > > analog computers don't do anything special -- they just obey the same
> > old
> > > laws of motion that they always do in any circuit. But the circuit is
> > > cleverly designed so that, when the electrons move according to their
> > > regular old laws of motion, their behavior matches the solution to a
> > > particular mathematical problem.
> > >
> > > In the same way, quantum computers are much less versitile than
> > ordinary
> > > digital computers. However, there are certain very restricted types
> > of
> > > problems on which they (like analog computers) out-perform digital
> > > computers. Electrons in a quantum computer aren't doing anything
> > weird
> > > (or perhaps I should say, not doing anything weirder than they do all
> > the
> > > time in any ordinary atom or molecule). However, in a quantum
> > > computer, the clever designers set up the system so that when the
> > > electrons (or photons) obey the same old ordinary laws of motion that
> > they
> > > always do, their behavior matches the solution to a particular
> > > mathematical problem.
> > >
> > > When someone builds a clever classical-physics device such that its
> > > mechanical or electrical behavior matches the solution to a tricky
> > > computation problem, we don't feel any need to invoke parallel
> > universes.
> > > Nor should we. Nor is there any such need when someone builds a
> > clever
> > > quantum-physics device such that its behavior matches the solution to
> > a
> > > tricky computational problem.
> > >
> > > Someday, physicists might find a way to distinguish experimentally
> > > betwen Copenhagen, many-worlds, non-local hidden variable, and other
> > > interpretations of quantum mechanics.
> > > But we haven't yet.
> > >
> > >
> > > Loren Haarsma
> > >
> >
> >
>
Received on Fri Mar 3 08:47:41 2006