Flaminia Giacomini (ETH Zurich)

Quantum effects in gravity from a delocalised quantum source

Understanding the fundamental nature of gravity at the interface with quantum theory is a major open question in theoretical physics. Recently, the study of gravitating quantum systems, for instance a massive quantum system prepared in a quantum superposition of positions and sourcing a gravitational field, has attracted a lot of attention: experiments are working towards realising such a scenario in the laboratory, and measuring the gravitational field associated to a quantum source is expected to give some information about quantum aspects of gravity. However, there are still open questions concerning the precise conclusions that these experiments could draw on the nature of gravity, such as whether experiments in this regime will be able to test more than the Newtonian part of the gravitational field.
In my talk, I will first motivate why quantum information tools such as communication protocols can contribute to identifying quantum aspects of gravity in the low-energy regime. I will then present a new result, where a delocalised quantum source gives rise to effects that cannot be reproduced using the Newton potential nor with a known classical model of gravity. These effects can in principle be measured by performing an interference experiment, and are independent of graviton emission.
Identifying stronger quantum aspects of gravity than those reproducible with the Newton potential is crucial to prove the nonclassicality of the gravitational field and to plan a new generation of experiments testing quantum aspects of gravity in a broader sense than what proposed so far.