🚀 go-pugleaf

In article <1992Oct13.061724.25758@netcom.com>, rcain@netcom.com (Robert Cain)
writes:
> leichter@zodiac.rutgers.edu writes:
| : 
| : The attack against the *cryptosystem*, as opposed to the attack against QM,
| : goes like this:  The eavesdropper clones the photons and SAVES them - he
| 
| How does he do this?  I know of no way to "save" a photon.  Somehow mirrors
| would be involved and I think interaction with a mirror would alter the
| polarization state.
| 
Why?  How do you think Alice sends the photons to Bob in the first place?
Do you think they can only be propagated in a vacuum, with no mirrors,
lenses, or other objects in the way?  If so, this is hardly a very useful
system.

You should be able to transmit these photons through a fiber (which
contains them by total internal reflection) without losing the important
information.  The fiber can be wrapped into a ring; you need an optical
switch to get it into the ring at the start, and out at the end, but
such things exist.

Admitedly, keeping a photon going around a ring of fiber for, say, an
hour is pretty unlikely.  But remember that you can keep amplifying the
signal while retaining its information by using a laser - that was the whole
basis by which we cloned the original photon!  In effect, you are coupling
the original information to a laser pulse that you can keep feeding energy
into to make up for the energy it loses.  I see no fundamental reason why
you can't keep the information stable as long as you like this way.

							-- Jerry