Recent content by sheaf

If you take a source which generates a single photon at a time, and a long time interval between photons, and pass the generated photons through a double slit arrangement, you slowly build up the interference pattern. Unless each individual photon has a wavelike character (including a...

I would say that, yes, the wavelength attribute can be reasonably said to apply to a single photon. A photon is a single excitation of a mode of the electromagnetic field. A mode is a solution of Maxwell's equations satisfying whatever boundary conditions are appropriate. So for a single...

There are a number of subtleties in this post: 1) When you use the word "beam", it suggests that this is the light from a laser, or thermal source. In this case, the electromagnetic field constituting the beam is not in a state which has a definite number of photons. 2) The word "individual"...

Note that if the field is in a photon number eigenstate (definite number of photons), it does not look like a classical EM plane wave field - for example the expectation value for the electric field is zero. If you want to build a field which looks like a classical plane wave, you end up with a...

Available from project Euclid:

Tunneling maybe? :smile:

Guy Blaylock wrote a nice simple and very informative treatment of the two photon example.

Some work has been done on these issues: https://en.wikipedia.org/wiki/Bonnor_beam If the photons are traveling parallel but in opposite directions, they allegedly attract! Of course these calculations are presumably restricted to classical light, so the use of the term "photons" in this...

I've always taken the view: In-State = physics Stuff in between = mathematics to get the right transition amplitudes in<->out Out-State = physics Statements like "Quantum theory predicts that every particle spends some time as a combination of other particles in all possible ways. These...

Yes, in the past I've come across this paper by Greulich, which talks about the state of light from a source in which atoms "cooperate" http://www.fli-leibniz.de/www_kog/research/physics/SPIE.pdf (can't find it on the arxiv unfortunately).

I suspect that the problem is with the last sentence of the o/p. The Feynman propagator is appropriate for calculating S matrix elements i.e. time symmetric processes. The problem, as formulated, isn't time symmetric. Perhaps a treatment involving the retarded propagator could be given.

Perhaps the correct question to ask is "can quantum field states be entangled?" I would say yes, the vacuum state has been described as maximally entangled.

I'm confused about why Feynman's statement is seen as an error. The context was that he was talking about the double slit experiment with electrons to an audience who had (presumably for the most part) only ever seen classical mechanics and possibly classical wave theory, but for whom an...

The same symbol is presumably used because in the overlaps of coordinate patches, there is a duality between active and passive diffeomorphisms. See the discussion on P3 here for example. P(x) is the point on the manifold M with coordinates x. But yes...the active/passive thing is a bit...

Yes, there is a model in which one component is the pair production which happens behind the horizon with the positive energy particle tunnelling out: http://arxiv.org/abs/hep-th/9907001