[Elecraft] OT: Distinguishable angular momentum in radio photons?

[Stephen Prior]

I read a fairly comprehensive debunking of this some weeks/months ago, I
just wish I could remember where I read it, it might have been in one of
the physics publications I take at work, now probably buried under mounds
of other stuff!

I seem to recall that it picked up on pretty much the same points as Jussi
has written.
If I can find the source, I will post a link to it.

73 Stephen G4SJP


On 4 May 2012 20:02, Jussi Eloranta <jmeloranta at gmail.com> wrote:

> On 05/03/2012 10:10 PM, Erik Basilier wrote:
> > The May 2012 issue of the IEEE Spectrum magazine reports that
> researchers in
> > Italy and Sweden were able to conduct two separate instances of radio
> > communication on the exact same frequency, without increasing bandwidth,
> and
> > without time-division multiplexing, be making the transmissions differ in
> > angular momentum. One transmission used linear polarization, and the
> other
> > was given angular momentum by means of a dish with a radial cut, where
> the
> > metal  was bent backwards/forwards on the two sides of the cut.
> Apparently
> > this is not just a case of linear vs circular polarization, as circular
> > polarization can be readily picked up by a linearly polarized antenna,
> and
> > apparently the two channels did not interfere with each other. The
> > researchers claim that this demonstration points to the possibility that
> the
> > radio photons can be given multiple, quanized levels of angular momentum,
> > making possible several more communication channels without increased
> > bandwidth. Other researchers say that this is just a form of MIMO.
> Wikipedia
> > describes MIMO as the technique of using multiple antennas as in
> diversity
> > reception or in gain increases obtained by phasing the antennas.
> >
> The only source of angular momentum in a photon is its intrinsic spin (
> = 1). This can have two projections, +1 and -1 (only two, unlike for
> most spin one particles, which have three possible projections).
> However, these two projections are directly related to the left and
> right circularly polarized light, so I cannot quite see what other
> source of angular momentum could arise in this case? Having said this, I
> don't quite believe in the Swedish group explanation of this experiment.
>
> Jussi Eloranta
> AA6KJ
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>