Quantum entanglement

Physics

Gravitation

Spacetime

Mathematics

Mathematical physics

Lorentz transformation

Particle physics

Graviton

Unitarity

Geometry

Theoretical physics

Massless particle

Quantum mechanics

Lorentz covariance

Scalar (mathematics)

Hilbert space

Classical mechanics

Boson

Quantum

Physical review. D/Physical review. D.

Many experiments have recently been proposed to test whether non-relativistic gravitational interactions can generate entanglement. In this note, 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.

Newton, entanglement, and the graviton