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

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 08:46:37 2006