Entanglement dynamics in de Sitter spacetime

We apply the master equation with dynamical coarse graining approximation to a pair of detectors interacting with a scalar field. By solving the master equation numerically, we investigate evolution of negativity between comoving detectors in de Sitter space. For the massless conformal scalar field, it is found that a pair of detectors can perceive entanglement beyond the Hubble horizon scale if the initial separation of detectors is sufficiently small. At the same time, violation of the Bell-CHSH inequality on the super horizon scale is also detected. For the massless minimal scalar field, on the other hand, the entanglement decays within Hubble time scale owing to the quantum noise caused by particle creations in de Sitter space and the entanglement on the super horizon scale cannot be detected.