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QM started as a non-relativistic theory for microscopic particles. Then there were the attempts to make it relativistic and the results of those attempts suggested that you can't have a relativistic system with a fixed number of particles.
But things are a bit different for photons. A non-relativistic theory for photons is meaningless simply because they are light itself! And so an attempt for getting a quantum theory for light, directly leads to a QFT(QED).
This is OK for the days that QED was young, because people could do experiments on only many-photon systems but nowadays technological advances allow physicists to study a single photon in labs. And that's the thing which is confusing for me!
How they have single photons? How is it that that single photon remains a single photon and after some time, you don't have a different number of photons with lower frequencies?
Or maybe I should add to the above two questions: "... for a long enough time that physicists can study only a single photon"!
My other question is, what does "single photon QED" look like? Its just as trivial as having only states, that are built by acting on vacuum state by a photon creation operator once? Or there are other things to it?
Thanks
But things are a bit different for photons. A non-relativistic theory for photons is meaningless simply because they are light itself! And so an attempt for getting a quantum theory for light, directly leads to a QFT(QED).
This is OK for the days that QED was young, because people could do experiments on only many-photon systems but nowadays technological advances allow physicists to study a single photon in labs. And that's the thing which is confusing for me!
How they have single photons? How is it that that single photon remains a single photon and after some time, you don't have a different number of photons with lower frequencies?
Or maybe I should add to the above two questions: "... for a long enough time that physicists can study only a single photon"!
My other question is, what does "single photon QED" look like? Its just as trivial as having only states, that are built by acting on vacuum state by a photon creation operator once? Or there are other things to it?
Thanks