Can we detect gravitons this way?

Question

First, we shoot a collection of particles (let's exclude gravitons from these, just for the sake of clarity) through a large region of spacetime in which the stress-energy tensor is zero and make them impact on a screen somewhere far away. A pattern will emerge.
Then we do the same with a second collection of particles (as much as possible identical to the first collection) but this time a gravitational wave is present.
We can vary a number of things. We can choose different particles (from photons to atoms). We can let the momenta of the particles have different angles (though they all are moving parallel wrt each other) wrt the direction in which the gravitational wave propagates. The same can be done but wrt to the screen. You can also vary the distance between the screen and the wave. The same can be done for the source of particles. For sure there will be different patterns visible in both cases. For example when the screen is placed far enough. Or not? Is it possible to detect gravitons with this construction (or, equivalently, to rule them out)?

ultrapoci · Answer

I don't think you can produce gravitational waves at will. At least, strong enough to be measurable. Also, the setup used to measure gravitational waves is extremely sensitive and precise, because they are very weak. Noticing if a gravitational wave has any impact on a beam of particles is basically impossible at the moment, considering on top of everything else that those same particles will interact with each other with other forces.

Answered by ultrapoci on May 22, 2021

anna v · Answer

The problem is not the particles, it is that one cannot control and focus a gravitational wave. The gravitational waves detected by LIGO, the first evidence of gravitational waves, were coming from the merging of two black holes  .
There is no way to detect or predict such occurrences, and the LIGO "screen" is continents long.
Gravitons are another layer of complexity , at the moment experiments are trying tof find their existence through polarization of the cosmic microwave background radiation. Having a beam of individual gravitons interact with individual particles is science fiction.

Anders Sandberg · Answer

You are describing LIGO: a beam of photons is sent through an empty region and allowed to interfere with a reference beam. When gravitational waves arrive they cause a shift of the interference fringes.
You may want the wave to be fully inside the test chamber rather than affecting it as a whole, but note that the effect of the wave - periodic changes in the distance to the target - happens in either case.

Can we detect gravitons this way?

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