# Bra-ket wormholes Bra-ket wormholes are (Euclidean) wormholes that connect a Euclidean path integral that [[0207 Euclidean state preparation|prepares]] a ket and one that prepares a bra in the [[0555 Gravitational path integral|gravitational path integral]]. Allowing this to appear obviously changes the inner products of the states, but this fact is curiously a very special feature of the gravitational path integral and quantum gravity in general. It is believed that the corrections to the inner products can be a key to understanding the finiteness of the Hilbert space of quantum gravity. ## Refs - [[2020#Anous, Kruthoff, Mahajan]] - [[2020#Chen, Gorbenko, Maldacena]] - [[2022#Milekhin, Tajdini]]: include Casimir energy - [[2024#Fumagalli, Gorbenko, Kames-King]]: de Sitter