Newton, entanglement, and the graviton

Many experiments have recently been proposed to test whether nonrelativistic gravitational interactions can generate entanglement. In this paper, I consider the extent to which these experiments can test if the graviton exists. Assuming unitarity and Lorentz invariance of the S-matrix, I demonstrate that this Newtonian entanglement requires the existence of massless bosons, universally coupled to mass, in the Hilbert space of low-energy scattering states. These bosons could be the usual spin-2 gravitons, but in principle there are other possibilities like spin-0 scalar gravitons. I suggest a concept for a more refined experiment to rule these out. The special role of d = 3 + 1 spacetime dimensions and the possibility that unitarity is violated by gravity are highlighted.

Automated summary

This paper focuses on discussing whether recent experiments can test the existence of gravitons and proposes a more refined experiment concept. It is demonstrated that Newtonian entanglement requires the existence of massless bosons universally coupled to mass.