Real-space entanglement in the Cosmic Microwave Background

Understand

We compute the entanglement entropy, mutual information and quantum discord of the Cosmic Microwave Background (CMB) fluctuations in real space.

• To that end, we first show that measurements of these fluctuations at two distinct spatial locations can be described by a bipartite, continuous Gaussian system.
• This leads to explicit formulas for the mutual information and the quantum discord in terms of the Fourier-space power spectra of the curvature perturbation.
• We then find that quantum entanglement, that builds up in Fourier space between opposite wave momenta as an effect of quantum squeezing, is transferred to real space.