Self gravity decoheres quantum systems

Abstract

We study the effects of self gravity on the quantum state of a massive and static particle that initially contains quantum coherence between two positions. We employ linearized quantum gravity to obtain the self-interacting dynamics of the particle mediated by gravitons, and find that the effective evolution of the particle's state can be viewed as a quantum channel composed of a unitary, dephasing, depolarizing, and erasure part. Depolarization drives the state towards maximal mixedness while depolarization and dephasing decrease its quantum coherence. Crucially, the intrinsic diffusion and dephasing timescales of the problem determine a relation between the mass and size of the particle that naturally identifies the transition between its classical and quantum regime. Our work therefore provides an explanation for the observational difference between the quantum behavior of small and light systems and the classical behavior of larger and heavier ones.

5 pages and 26 pages of supplementary material. 10 figures