quantum hype

[Peter Fairbrother]

Peter Fairbrother wrote:
 
> If the channel is authentic then a MitM is hard - but not impossible. The
> "no-cloning" theorem is all very well, but physics actually allows imperfect
> cloning of up to 5/6 of the photons while retaining polarisation, and this
> should be allowed for as well as the noise calculations. I don't know of any
> existing OTS equipment that does that.
> 
> A lasing medium can in theory clone photons with up to 5/6 of them retaining
> enough polarisation data to use as above, though in practice the noise is
> usually high.
> 
> There is also another less noisy cloning technique which has recently been
> done in laboratories, though it doubles the photon's wavelength, which would
> be noticeable, and I can't see ofhand how in practice to half the wavelength
> again without losing polarisation (except perhaps using changing
> gravitational fields and the like); but there is no theory that says that
> that can't be done.

Had two requests for links (and some scepticism) about this already. Try:

http://www.photonics.com/spectra/research/XQ/ASP/preaid.44/QX/read.htm

for an article and some ref's (though I'm not even sure if the paper
referred to is the one I'm thinking of, the one with wavelength doubling. I
though it was published earlier this year).

I'll try and post some better links later.


-- 
Peter Fairbrother

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