Title: How general relativity causes unitary quantum dynamics to break down in a nano-scale experiment.
Speaker: Dr Jasper van Wezel (Cambridge,UK)

Abstract:The symmetries that govern the laws of nature can be spontaneously broken, enabling the occurrence of ordered states. Crystals arise from the breaking of translation symmetry, magnets from broken spin rotation symmetry and massive particles break a phase rotation symmetry. Mathematically, all of these cases can be described as an infinite sensitivity of the symmetric ground state to even infinitesimally small perturbations by a symmetry-breaking field. We have recently shown that also the unitary symmetry governing time evolution in quantum mechanics can be spontaneously broken in precisely the same way [1-3], as a consequence of an infinite sensitivity of certain quantum states to even infinitesimally small perturbations of the unitary Schrödinger equation.
In this seminar I will argue that such perturbations may arise in massive quantum states as a consequence of gravitational effects. I will show how they lead to the spontaneous breakdown of unitary time evolution, and discuss the experimental consequences. I will also suggest a possible experiment based on recent work on nano-scale mechanical resonators, which may be able to experimentally probe this new dynamics.