# Probing A Gravitational Cat State: Theoretical Problems And Experimental Prospects

**Abstract**: A gravitational cat state refers to the gravitational field sourced by a mass density in a quantum superposition of two position states. The first part of the talk will begin with an overview of the "grav-cat" setup proposed by Anastopoulos and Hu in [1], a setup that's based on standard Newtonian quantized gravity. The quantum measurement problem and Roger Penrose's influential argument against quantum superpositions of the gravitational field will then be presented as reasons to doubt the veracity of the predictions of standard Newtonian quantized gravity for the grav-cat setup. The second part of the talk will begin by presenting a modest response to the measurement problem and Penrose's argument, a semiclassical Newtonian gravitational model based on the GRW objective collapse theory [2, 3], which will then be applied to the grav-cat setup and shown to make different predictions than standard Newtonian quantized gravity [3]. The limitations of the semiclassical model will also be pointed out. Finally, an experimental scheme proposed by Derakhshani-Anastopoulos-Hu [4] for preparing and probing a gravitational cat state will be reviewed.

[1] C. Anastopoulos and B. L. Hu, Probing a Gravitational Cat State, Class. Quantum Grav. 32, 165022 (2015) https://arxiv.org/abs/1504.03103

[2] M. Derakhshani, Newtonian Semiclassical Gravity in the Ghirardi-Rimini-Weber Theory with Matter Density Ontology, Phys. Lett. A 378, 14-15, pg. 990 (2014) https://arxiv.org/abs/1304.0471

[3] M. Derakhshani, Probing Gravitational Cat States in Canonical Quantum Theory vs Objective Collapse Theories, 2016 https://arxiv.org/abs/1609.01711

[4] M. Derakhshani, C. Anastopoulos, and B. L. Hu, Probing a Gravitational Cat State: Experimental Possibilities, Journal of Physics: Conference Series, 701, conference 1 (2016) https://arxiv.org/abs/1603.04430

**Series:**IQIM Postdoctoral and Graduate Student Seminar Series