Re: Layman's Guide to Quantum Entanglement

From: Dave Jarvis (dave_at_nospam.net)
Date: 07/30/04 

Date: Fri, 30 Jul 2004 03:32:01 GMT

Hi, Half Pint.

Great questions. I've tried my best to answer them. Would be great if
someone else would back me up or tell me where and why I've gone wrong.

> Subsituting cake for grapes.
> If a big cake 'hits' a runner, can he take a quantum bite
> and leave the rest? Or must wait for a smaller cake?
> So can he have is cake and eat it? (So to speak).
> Actually you did answer this
> (for example, an apple weighing 250 grams is edible, but 216 grams is not).
> Well almost, what if it is a 300 grammer? can he eat 250g and throw the core
> away? (oops back on apples, your switch from grapes to apples might be
> confusing, (especially if you are a vegetarian)).

I did a search for the word "grape" and couldn't find any occurance in
the article (same with "cake", for that matter). To my knowledge, a
vegetarian would eath both grapes and apples. Now I think what you're
getting at is the following:

1. An electron "eats" a photon of 10 energy units.
2. The electron "spits out" a photon of 5 energy units.
3. Eventually it "spits out" the other 5 energy units, to return to
ground state.

I don't know if it can emit a little bit at one time and then a little
bit later. That's a good question for someone who has actually done
these experiments. :-)

> Looks like two magnets and one magnetic field to me!! Make your
> mind up.

There is a field that has influence from the north magnet, and a field
that has influence from the south magnet. To quote myself:

"... influence of the two magnetic fields (the S and N rectangles)".

I will clarify this, thank you. :-)

> Anyway the more important bit, I am a bit confused by spin, is it the
> same as charge?

I don't believe it is.

> so I cant say, but it would move either in or out, not up or down
> the screen as indicated. Are you saying it would move up or down
> as well as in (or out)?

As I haven't actually done any of these experiments, I don't know for
sure. I am, however, positive that I'm saying it only deflects up or down.

> Also I have never seen a light beam deflected by a magnet.
> Why don't bincoculars use magnets instead of prisms to
> 'bend' light?

This is a good point. Although I don't actually state that a photon
acts this way under a magnetic influence (I use the word "particle", but
I also state that a photon is a particle earlier on in the article), I
can see where there is room for confusion. Again, I will clarify this.
  Thanks!

> I don't get the bit about forwards and backwards spin for
> light either.

Yes, this can use some clarification. To my understanding, an object
can spin in any of 10 ^ 33 (10 to the power of 33) directions. However,
  particles have limits to the amount of spin that can be applied. Once
we choose an axis there are only 2J + 1 ways to put a fraction of spin
on the particle. (The value of J can be 1/2, 1, or 3/2 depending on the
particle.) So for a spin 1/2 particle, the units are +1/2 or -1/2,
which are known as "spin up" and "spin down."

For a massless spin 1 particle, it can be +1, 0, or -1. For any spin 1
particle (such as a photon), because it is always travelling at the
speed of light the only axis worth talking about for orienting the spin
of the particle is its direction of motion. Since 0 spin is meaningless
(it would indicate the photon's axis doesn't exist), people talk about
photons in terms of spin +1 or -1, which are also sometimes referred to
as spin up and spin down, but I prefer to use the distinguishing words
"left-handed" and "right-handed".

> I am planning on stealing some of these magnets to see if
> I can bend any light with them!!!

I don't believe magnetism will affect a photon's path. Other particles,
yes. I could also be wrong on this, and if I am, I certainly do hope
someone will correct me.

> Or maybe you can?
> http://www.wonderquest.com/extinctions-safetyglass-magnetslasers.htm

Technically it isn't a photon that is being redirected. The photon is
momentarily transitioning into an electron and positron pair (they might
even be entangled?), whereupon the magnetic influence does apply,
changes direction, and recombines into a photon. The net effect,
glossing over the transition phase, is that a magnet is able to change
the direction of the light beam. It cheats by making it an electron
first. :-)

> I like the bit about light being an electron and a positron, don't
> these particles have mass? and light has no mass??

E=mc^2

However, in this case, the electron-positron Frankenparticlepair would
likely conserve the total energy that was originally present in the
photon. I'm guessing they both lose a little speed and gain a little
touch of Higgs.

> Also doesn't a partical with mass (electron) at the speed have light
> have an infiniite mass?

First, an object with infinite mass would take an infinite amount of
energy to move. And I'd wager you won't find an infinite amount of
energy in our Universe. ;-) By this argument we can deduce that the
original premise that an electron can move [through a vacuum] at the
speed of light is incorrect. You can verify the answer on the 'Net.

> Also as they have opposite charges they would move apart, so how
> do they recombine?????

I don't know if your first presumption is correct. If it is correct, I
don't know how they recombine. My guess is that when they annihilate
each other, they spit out a photon, or photons, that conserve the energy
and angular momentum present with the first photon. Good question!

> Also when they change into particles with mass they must slow down?
> thus magnetic fields must slow the speed of light?

I would say, "Yes, the particles must slow down." But since the
particles are no longer photons, I can safely say that the magnetic
field does not slow light down. The net effect may be that the light
appears to momentarily slow down, but technically, again, it is the
electrons that slow down.

> Also there is the bit about the photon ending up as two photons,
> this is the bunch of grapes splitting into two, which can't happen?

Ah, this part I'm sure I explained. Perhaps it still needs
clarification. When the original photon is emitted from the electron,
after fighting its way through beta Barium Borate, there is the
probability that it will be emitted as (decay into) two photons.

This is like saying the electron "spits out" two photons at the same
time, and if they were to constructively interact, the sum of their
interactions would equal the exact properties of the original photon.

You lost me with the grapes. ;-)

Dave

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