Quantum Gravity: Parameters for Detection via Spin Entanglement and Theoretical Models

Quantum gravity is crucial for unifying general relativity and quantum mechanics, which are two of the fundamental pillars of physics. Despite the significant advances in theoretical models of quantum gravity, experimental validation of these theories remains sparse. This review paper aims to address this gap by examining the experimental proposal by Bose et al., that aims to show the non classicality of gravity, alongside a discussion of semiclassical and quantum models and their shortcomings. We explore the Double Stern-Gerlach experiment to observe gravitational entanglement, detailing the procedure and the quantum states involved. The minimization of Casimir-Polder forces, which could interfere with the experiment, is highlighted as essential for optimizing conditions for maximal entanglement, calculated using von Neumann entropy, and measured using an Entanglement Witness. We discuss the inferences drawn from this experiment and introduce semiclassical gravitational models, outlining the assumptions made by Bose et al. Furthermore, we delve into perturbative Quantum Gravity (pQG) using the path integral approach, explaining its non renormalizability and the extent of its applicability. The conclusions indicate that observing entanglement would demonstrate the non-classicality of gravity. While semiclassical models are experimentally inaccurate, they serve as useful calculational tools for black hole physics. Although pQG has proved to be non-renormalizable so far, it functions as an effective field theory (EFT) at energies below 1019 GeV.