Faster Light: Casimir Vacuum & Quantum Tunnelling

[Dmitry67]

http://en.wikipedia.org/wiki/Faster...t_.28Casimir_vacuum_and_quantum_tunnelling.29

I know the standard objection to tunneling experiments (group velocity), however, I have 2 questions.

1. Why WIKI section about it is kinda open-ended (not saying that issue is closed, no FTL is observed)

2. I fail to understand how that standard objection works if we send 1 photon at a time.

 

[SpectraCat]

http://en.wikipedia.org/wiki/Faster...t_.28Casimir_vacuum_and_quantum_tunnelling.29

I know the standard objection to tunneling experiments (group velocity), however, I have 2 questions.

1. Why WIKI section about it is kinda open-ended (not saying that issue is closed, no FTL is observed)

2. I fail to understand how that standard objection works if we send 1 photon at a time.

I think it fails for the same reason these things always fail ... they are based on occurrence or non-occurrence of events .. i.e. tunneling either happens or it doesn't. To an observer with a space-like separation from the source, no information can be reconstructed based on any FTL components of the signal until she compares what was received with what was transmitted.

 

[Dmitry67]

Well, there is no entanglement involved, the information channel is "normal" is tunneling experiments (I am playing devil's advocate)

 

[SpectraCat]

Well, there is no entanglement involved, the information channel is "normal" is tunneling experiments (I am playing devil's advocate)

I didn't say anything about entanglement ... my response was really aimed at he "1 photon at a time" example you gave. In that case, only a small fraction of the photons will tunnel, and it is impossible to know a priori which ones will tunnel, so you need to know both the incident and the transmitted photon trains in order to transmit information over such a channel. Thus it fails at FTL communication for the same reason that the entanglement implementations do.

 

[Dmitry67]

(continuing to play devils advocate).

Correct, only small percentage of photons will be registered behind the gap. But using even a single photon I can send some information (by polarization). So, if I send information using such channel, it will succeeds only in, say, 0.01% of cases. But I will claim that in 0.01% of cases I *had* FTL communication as I was able to decode information, encoded in momentum of these lucky photons.

 

[SpectraCat]

(continuing to play devils advocate).

Correct, only small percentage of photons will be registered behind the gap. But using even a single photon I can send some information (by polarization). So, if I send information using such channel, it will succeeds only in, say, 0.01% of cases. But I will claim that in 0.01% of cases I *had* FTL communication as I was able to decode information, encoded in momentum of these lucky photons.

I don't see how that would work ... say your polarization setup for information is H=1 V=0 for polarization states of the photons. As the sender, you have no idea which photons will end up being transmitted over the FTL tunneling channel, so you have no way to encode your information in the signal. The observer has the inverse problem .. yes, I am getting a photon every now and then, so I can read a string of 0's and 1's, but I have no idea how to interpret it.

Also, I am not sure how the tunneling experiments affect polarization ... for example, the frustrated total internal reflection experiment with the split prism seems like it would affect H and V polarized photons differently.

 

[Demystifier]

(continuing to play devils advocate).

Correct, only small percentage of photons will be registered behind the gap. But using even a single photon I can send some information (by polarization). So, if I send information using such channel, it will succeeds only in, say, 0.01% of cases. But I will claim that in 0.01% of cases I *had* FTL communication as I was able to decode information, encoded in momentum of these lucky photons.

Now I will play a devil advocate of a devil advocate.

If that counts as travel of information, than a pure random guess (that succeeds in 0.01% cases or more) is also a travel of information. But we know that the latter isn't a travel of information, so the former isn't it as well.