Constraining the fundamental number of quantum degrees of freedom using gravity

Speaker: Harshit Verma
Affiliation: University of Queensland

Abstract

"How many quantum degrees of freedom (DOF) are present in the universe?” is a fundamental open question in Physics. I will discuss how gravity can be used to approach this important question, elaborating on the interplay between quantum mechanics and gravity in the process. This quest is grounded in a series of recent works focusing on the low energy regime which explore the effect of gravity on quantum systems, manifesting as time dilation of an evolving quantum DOF. I will introduce the phenomenon of gravitational decoherence of a spatial superposition arising from this formalism and widen its scope to include extended quantum systems (EQS), while highlighting the key differences this exercise entails. Finally, using spin chain as a toy model for EQS, I will present the number of independent EQS which can cause reasonable decoherence in the spatial superposition of the massive particle. The coherence observed in an actual experiment can, therefore, be used to constrain the number of quantum DOF surrounding the spatial superposition of a massive particle, thus answering the aforementioned open question.