An entanglement-based test of quantum gravity using two massive particles
Istituto Nazionale di Ricerca Metrologica (INRIM)
Sala Riunioni, Palazzina A (II piano)
University of Oxford
All existing quantum gravity proposals share the same deep problem. Their predictions are extremely hard to test in practice. Quantum effects in the gravitational field are exceptionally small, unlike those in the electromagnetic field. The fundamental reason is that the gravitational coupling constant is about 43 orders of magnitude smaller than the fine structure constant, which governs light-matter interactions.
In this seminar I shall discuss a recent proposal (https://arxiv.org/abs/1707.06036), which is based on a radically different, quantum-information-theoretic approach to witness non-classical features of the gravitational field. The proposal consists of two parts.
The first part is an argument showing that any system (e.g. a field) capable of mediating entanglement between two quantum systems must itself be quantum.
The second part is a proposed experiment to detect the entanglement generated between two masses via gravitational interaction.
By the argument presented in the first part, the degree of entanglement between the masses is an indirect witness of the quantisation of the field mediating the interaction. Remarkably, this experiment does not require any quantum control over gravity itself. It is also closer to realisation than other proposals, such as detecting gravitons or detecting quantum gravitational vacuum fluctuations.