# 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.

### About Physics Seminars

The weekly Physics Seminar series focuses on a broad range of physics research within SMP, along with frequent presentations from visiting researchers. Seminars are usually scheduled for 1.00pm on Tuesdays.

The talks are typically more specialised than a colloquium but are often attended by staff and PhD students across a broad range of areas. Speakers are thus encouraged to include introductory material in the talks.

All SMP researchers and HDR students are encouraged to speak. Please email Tyler Neely to register your interest.

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### Venue

https://uqz.zoom.us/j/94116861984