  We study the deep connections between the concepts of quantum information
theory and cosmology. Employing Fermi normal coordinates and conformal Fermi
coordinates, we construct a relation between Friedmann equations of
Friedmann-Lemaitre-Robertson-Walker universe and entanglement. Friedmann
equations are derived with the first law of entanglement under the assumption
that entanglement entropy in a geodesic balls is maximized at fixed volume.
