Here's a faster than light issue I have:

Take a really weak light source. Aim it at a beam splitter, say, at 45 degrees to the line of the light. Assume that the light source is so weak that typically we get a photon only one a second or so (not strictly necessary for the idea).

Then each photon (there are standard claims that could also use an electron, proton, neutron, etc. but all photons travel at the speed of light, and using just light we don't have to worry about the electric charge of an electron or proton) has a quantum mechanical wave function. From the lessons we get from Young's double slit, the Michelson-Morley experiment, the Mach-Zehnder interferometer, the Fabre-Perot interferometer (right, my ugrad physics prof liked optics!), we believe at the beam splitter the wave function becomes two parts, one part continuing straight through the beam splitter and the other part going off at 90 degrees.

Now sit and have a brewski or two; finish a physics Ph.D.; get married; have a lot of kids; get them all through college; and, I omitted, for the beam that went through the beam splitter, have it bouncing around in a box full of perfect mirrors or resting in some Bose-Einstein condensate, and then get out a very sensitive photo detector and try to detect the photon.

Okay, for a perfect beam splitter, have a 50% chance of detecting the photon. Suppose we do, or, suppose we just in the beginning did this stuff for 1000 individual photons and pick one of the photons where we do get a detection from the part of the wave function close to us (the other half of the wave function is way past the nearest star by now).

So, we get our detection. We know the energy we get, just proportional to the frequency of the light. So, our detector gets it all -- the wavelength, the frequency, the momentum, the energy, maybe the polarization. Fine.

Now, folks, what the heck happens to the other half of the wave function, the half that went 90 degrees and by now is part way out of the galaxy?

No sense in saying that half just disappeared. For one, ET way out there 50% of the time could detect the photon. For another, we could have a mirror out there and have that half of the wave function return to us and do a Young's double slit or Michelson-Morley experiment where both parts of the wave function definitely get involved. So, no saying that the half of the wave function nearly out of the galaxy doesn't matter.

I know; I know; that half of the wave function gets old and tired, goes de-coherent, etc., but such stuff raises other little issues such as conservation of energy. So let's assume that, even after all these years, both parts of the wave function are still nice and healthy just like they would have been in Young's double slit, the Michelson-Morley experiment, etc. Besides we believe we can detect photons 13.8 or so billion years old, and, really, some of those may have their wave functions, from being deflected here and there for all those years, in multiple parts.

But we know also that we and ET can't both detect the photon. So, that part of the wave function out there with ET can't just do its own thing -- with us and ET, there will be exactly one detection.

Okay, when we get the detection, supposedly the other half of the wave function, some light years out there where ET is, disappears, folds up, evaporates, leaves town, becomes null and void, instantly, just as soon as we make our detection. So, sorry guys, that looks like an instantaneous effect (I didn't say communications) over a distance of light years. So, the naughty boy in his room running the simulation for our universe, as soon as we detect the photon, has to run around all over the whole darned universe and clean up any stray pieces of the wave function of the original photon, and there may be thousands of those. During this clean up, the whole simulation (think of a data base problem!) has to stop. So, the simulation has to run all over the universe or a lot of it in zero time -- that's an effect infinitely fast!

I know; I know; this is not faster than light travel for us, but it looks like faster than light travel for the naughty boy's universe simulation program.

Now from this, what can we say about how the quantum fields we believe in actually have to work? Is there something?

E.g., suppose both we and ET have really sensitive gravitational wave detectors and, thus, can detect each of the two pieces of the wave function as they pass by. Uh, the photon has to feel gravity and also create gravity, and, thus, BOTH parts of the wave function have to create gravity. So that part of the wave function that ET gets MUST create a gravitational wave as it passes by and MUST create a gravitational wave as it disappears instantly as we detect the photon. We're getting close to faster than speed of light something or other ...!

Okay, suppose ET is 10 light years away and we want to spend the next 10 years setting up an instantly fast communications channel.

We agree to send one bit a second.

We use the beam splitter, ..., etc. as above.

If we are using our elecgtro-magnetic detector, the for each photon we have not detected, ET gets both a gravitational wave detection and a photon (electro-magnetic) detection.

For each photon we do detect, ET gets neither the gravitational nor the electro-magnetic detection.

If we put our detector in the path of our half of the wave function, then we get a detection half the time which means that half the time ET gets neither a gravitational nor an electro-magnetic detection.

If we do not have our detector in front of our half of the photon, then ET always gets the gravitational signal and half the time gets the electro-magnetic signal.

So, suppose each second (since when we started spending 10 years setting up the communications channel) we sent 1000 photons a second.

Now for one of those seconds, if we are using our electro-magnetic photon detector, ET gets about 500 gravitational wave detections and 500 electro-magnetic detections. If we are not using our photon detector, then ET gets 1000 gravitational wave detections and 500 electro-magnetic detections. So, once we have spent 10 years setting up the communications channel, we can communicate at data rate of 1 bit a second with ET instantly.

I don't really believe it, but first cut it looks that way!

Now each second, we either put our detector in the path of our half of the wave function or we don't.