Gravitational Decoherence

Tuesday, March 27, 2018
Lorenzo Asprea, PhD student, University of Trieste
One of the greatest predictions of general relativity is the existence of gravitational waves (GWs), which can be thought of as small perturbations of the metric propagating through spacetime at the speed of light. They are of fundamental interest in many branches of physics, such as cosmology, theoretical physics and astrophysics, and their recent first detection has opened new thrilling horizons for the research and a huge effort is being put into the construction of ever more sophisticated detectors. Most gravitational waves that arrive on Earth are produced by different unresolved mechanisms and sources, and thus result into a stochastic perturbation of the flat spacetime background. Within the framewoerk of quantum theory, this altered background affects the dynamics of matter propagation and ultimately leads to decoherence effects as typical of any noisy environment. The decoherence effect of a stochastic perturbation of the metric has been studied by several authors, each of whom has produced their own model for the evolution of off-diagonal elements of the density matrix of a quantum state or, more generally, the loss of interference in the system. However, that of giving a universal and meaningful description of the phenomenon is still an open problem, as the different models so far proposed refer to particular regimes of approximation and thus seem to lead to different predictions on the preferred decoherence basis or on the effective measureability of the loss of coherence in a real experiment. In this talk I will present a still under development original model regarding the gravitational decoherence for fermionic particles in the non relativistic regime, as I will also comment on some of the models for bosonic particles that are present in the literature