Re: speed of light


laura wrote:
> I don't mind to use only one photon.
>
> I mean, the problem is that if I use only one photon, maybe it's hard
> to be detected...
>
> And what happens if the photon is divided into 2 photons? Is this
> possible?

Not that I know of - at least not in any useful way. Non-linear
crystals allow frequency-doubling, where two photon fuse to make one
photon of twice the frequency (half the wavelength), but I don't think
that works the other way around. In theory, you could hit a molecule
with the right energy to promote it into a energy state that was two
quantum steps above the ground state, and hope that it would emit two
photons in the process of relaxing back to the ground state, but this
isn't an instantaneous process.

> Sometimes, in my device I need to do this. And the photons will go on
> different paths. And some of them will get earlier to the destination
> and others will get later....

Are you thinking about quantum cryptography? Page 18 of the review
below
discusses single-photon detectors ....

http://arxiv.org/PS_cache/quant-ph/pdf/0101/0101098.pdf

----------
Bill Sloman, Nijmegen

.

Relevant Pages

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