This is related to his research. His latest podcast goes to it more deeply (there is a transcript): https://www.preposterousuniverse.com/podcast/2019/09/09/63-s...

The goal is to derive emergent spacetime and gravity from quantum mechanics.

Some features of their theory:

* Finite dimensional Hilbert space. Quantum field theory gets boot.

* Spacetime is entangled degrees of freedom in a way that semi-classical spacetime geometry emerges. Things are local because they are entangled not the other way around.

* Spacetime expands because initially untangled degrees of freedom become entangled with the rest of the the universe.