[14231] in cryptography@c2.net mail archive
Re: quantum hype
daemon@ATHENA.MIT.EDU (Peter Fairbrother)
Sun Sep 21 13:05:00 2003
X-Original-To: cryptography@metzdowd.com
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Date: Sun, 21 Sep 2003 17:51:56 +0100
From: Peter Fairbrother <zenadsl6186@zen.co.uk>
To: <cryptography@metzdowd.com>
In-Reply-To: <BB935A11.39E88%zenadsl6186@zen.co.uk>
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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