Gravity-Matter Entanglement in Regge Quantum Gravity
  We argue that Hartle-Hawking states in the Regge quantum gravity model generically contain non-trivial entanglement between gravity and matter fields. Generic impossibility to talk about "matter in a point of space" is in line with the idea of an emergent spacetime, and as such could be taken as a possible candidate for a criterion for a plausible theory of quantum gravity. Finally, this new entanglement could be seen as an additional "effective interaction", which could possibly bring corrections to the weak equivalence principle. 
Nikola Paunkovi\'c and Marko Vojinovi\'c
gr-qc hep-th quant-ph