Impact of quantum entanglement induced by magnetic fields on primordial gravitational waves

Abstract

There exist observational evidence to believe the existence of primordial magnetic fields generated during inflation. We study primordial gravitational waves (PGWs) during inflation in the presence of magnetic fields sustained by a gauge kinetic coupling. In the model, not only gravitons as excitations of PGWs, but also photons as excitations of electromagnetic fields are highly squeezed. They become entangled with each other through graviton to photon conversion and vice versa. We derive the reduced density matrix for the gravitons and calculate their entanglement entropy. It turns out that the state of the gravitons is not a squeezed state but a mixed state. Although witnessing such an entanglement is not feasible at present, it would be an important experimental challenge.

27 pages, 6 figures

References in corpus (5)

• Entanglement entropy of $\alpha$-vacua in de Sitter space
• Cosmological Consequences of Initial State Entanglement
• Hanbury Brown-Twiss interferometry and second-order correlations of inflaton quanta
• Squeezed quantum states of graviton and axion in the universe
• Conversion of squeezed gravitons into photons during inflation

Cited by in corpus (1)

• A peak in the power spectrum of primordial gravitational waves induced by primordial dark magnetic fields