Nothing signifcantly new below, just improved form. There still seems to
be something of substance to this idea.
FTL by Down-converting (DRAFT #5)
A method is proposed here to achieve faster than light (FTL) communication
by the use of down-converters. A down-converter splits a photon into two
photons each having half the energy of the original photon.
Suppose we have a sender Alice, a receiver Bob, and an intermediary
facilitator Charlie. Charlie uses a beam splitter to create two beams of
laser light: L the left beam and R, the right beam. Charlie then
down-converts the L beam to create beams L1 and L2, and similarly creates
beams R1 and R2 from the beam R. Beams R2 and L2 are normal path or
"signal" photons through the down-converter, while beams R1 and L1 are
called "idler" photons. "Beam"here means a flow of individually detectable
photons sent in very short intervals so as to provide a useful rate of
communication. Charlie directs beams L1 and R1 to Alice and beams R2 and
L2 to Bob. The corresponding photons arrive at both Bob and Alice at
nearly the same time, but here assume Alice receives hers first, but just
barely before Bob.
Bob directs beams R2 and L2 such that they can create an interference
pattern in a set of detectors arranged so it is feasible to rapidly and
with high probability determine whether an interference pattern is present
or not. The signal photon beams R2 and L2 can create such an interference
pattern because they are the two paths from a beam splitter.
Bob will in fact see such an interference pattern provided Alice does not
put detectors in idler beams R1 and L1.[1] If Alice does place detectors
in both her beams, then this is equivalent to knowing which path each of
Bob's photons have traveled, and thus Bob can observe no interference
pattern. This known-path-no-interference result has been characteristic of
numerous versions of the two slit or two path interference experiments.[2]
If Alice sees an idler she knows which path the corresponding signal photon
took to Bob, and the interference wavefunction instantly collapses. Bob,
when his photons arrive shortly after Alice's corresponding photons, knows
the current state of Alice's detectors by whether he sees an interference
pattern or not.
Since Alice and Bob could be light years away from each other, and since
Alice thus might have years from the time Charlie released the photons to
make the choice to detect or not detect her photons, faster than light
communication from Alice to Bob is clearly a possible result. It might be
said that the communication can not be verified for years, but such
verification is in this case is not necessary. Bob does not require
verification or comparison to Alice's results to know the immediate state
of Alice's detectors, or to immediately detect a change of state of those
detectors, with sufficient speed and reliability to establish a practical
communication channel. Further, a similar channel can be established from
Bob to Alice, thus permitting immediate error detection and correction or
retransmission.
Assuming that beams adequate for fast communication can be generated and
the resulting interference detected sufficiently fast, achieving high data
rate FTL communication at short range then primarily boils down to how fast
Alice can switch from a detecting mode to a non-detecting mode. This might
be as simple as her redirecting beams R1 and/or L1, or by switching on and
off the information from her detectors. This experiment then, in addition
to achieving FTL communication, may be useful for determining exactly of
what an observation consists.
An experiment requiring the simplest possible message would involve sending
a data bit (actually only a change of state) via a one-way FTL
communication channel and returning it via a second one-way return FTL
communication channel, and repeating this process to establish an
oscillation. A fiber pair from Charlie to Bob and Charlie to Alice could
be used, if desired, to create a single FTL communication channel. A
similar set of fiber pairs would be used for the return channel. To
demonstrate FTL communication it is then necessary to transmit over a
sufficient distance D that the oscillation frequency, f, is faster than the
oscillation frequency F = c/D that can be achieved by light. A 10 km
communication link (each way) need only cycle faster than about 15 kHz to
break the light speed barrier. Assuming a sample of 100 photons to be
sufficient for determining interference, a photon transmission and
detection rate of 1.5 million photons per second is required. However, it
is not known what precisely constitutes an observation. It may be that
individual photon detection is not even necessary, but rather mere beam
intensity determination.
References:
[1] Kim et al, Phys. Rev. Lett., Vol 84, no. 1, pp 1-5
[2] Brian Green, *The Fabric of the Cosmos*, (New York, Alfred A Knopf,
2004), pp 193-197
Regards,
Horace Heffner
