Entanglement of Quantum Fluctuations in the Inflationary Universe

Understand

We investigate quantum entanglement of a scalar field in the inflationary universe.

• By introducing a bipartite system using a lattice model of scalar field, we apply the separability criterion based on the partial transpose operation and numerically calculate the bipartite entanglement between separate spatial regions.
• We find that the initial entangled state becomes separable or dis-entangled when the size of the spatial regions exceed the Hubble horizon.
• This is necessary condition for the appearance of classicality of the quantum fluctuation.