QED-induced decoherence in the quantum gravity induced entanglement of masses (QGEM) experiment

Contemporary research in physics focuses on unraveling the mysteries of quantum gravity, which has posed challenges due to the absence of empirical evidence. The question of whether gravity exhibits quantum behavior has ignited a debate. Traditional tests and cosmological observations have failed to provide definitive proof, prompting a shift towards laboratory investigations. The Quantum Gravity induced Entanglement of Masses (QGEM) proposal proposes a novel approach to detect the quantum nature of gravitational interactions through entanglement between test masses in matter-wave interferometers. This study demonstrates that observable entanglement can be generated between masses in a superposition state by using the quantum phase induced by gravitational interactions. By analyzing the linearized quantized version of Einstein's theory of gravity, the importance of off-diagonal terms in the coherent state basis of gravitational field modes for entanglement generation is identified. The proposal assumes that gravitational interaction is mediated by a quantum mechanical gravitational field. However, before the implementation of interferometry with nanoparticles becomes feasible, several experimental challenges must be addressed. These include the creation of spatial quantum superpositions, ensuring long coherence times, and mitigating external disturbances. The primary goal of this master's thesis is to investigate Quantum Electrodynamics (QED) decoherence in matter-wave interferometry with nanoparticles. This channel of decoherence is inevitable and must be considered even when dealing with neutral nanocrystals. Starting from the QED Lagrangian, we will derive the evolution of the density matrix and study the dipole-dipole interaction in both short and long wavelength limits. The derived formulas will then be applied to impose constraints on the crystal and environmental parameters within the QGEM protocol.