This is, as I have said a number of times, because the theory that describes photons, QED, the most accurately verified theory of all time, includes SR, where FTL signalling is explicitly forbidden. What I can say, and there is no room for doubt on this, if you could do it then the information could not be sent FTL.

I suggest you think about why you want to ignore it when doing so means you do not want to examine your ideas using the theory that describes photons.Īs to if you can shoot photons into a laser or something like that and from what it shoots out you can determine the spin of what goes in I have zero idea - you need to ask an experimental type.

The reason I introduce QFT is it immediately shows what you want to do cant be done. The above is the principle that forbids it. What precisely do you not get that a theory cant violate the premises its based on? QFT is based on SR - you cant do it - end of story. I have zero idea why one should need to invoke QFT to answer those questions. I already asked this in #4 and #12, which you chose to ignore. Since the spontaneously emitted photons produce only statistical noise, in one of the basis we should measure one eigenstate significantly more often than the other which would allow to deduce the state of the first photon.Īll I want to know is the error in this train of thought. Let's measure half the produced photons in the basis + and the other one in the basis x. Is it spontaneous emission? And if yes, why is it impossible to statistically infer the polarization of the first photon of a cascade even though there are more photons created in the same polarization than in any other?Īssume the polarization of the first photon to be an eigenstate of either the basis + or x. All I want to know is what physical process forbids the second to be used for the protocol formulated in the first. These two facts can be formulated without going any further into QFT or no-cloning (which is what I meant by putting them aside for a moment).

Stimulated emission creates a second photon of identical polarization and direction.

He can do so instantly after Alice's measurement, regardless the distance. If Bob is capable of cloning his photon, he can perform a tomography and deduce the basis Alice used.

The capability of copying the polarization of a photon would allow superluminal communication by using two entangled photons: Alice can choose to either measure her photon in the + or in the x basis and thereby make Bob's photon collapse into the same basis.

No clone theorem