Rotational superradiance is one of the most fascinating phenomena in black-hole physics. Here, with the aim of probing quantum properties of superradiance in the lab, we investigate the interaction of the acoustic waves with quantum vortices in Bose-Einstein condensates (BEC) in the framework of dissipative mean-field model. We find the conditions of the acoustic-induced quantum phase slips in condensates with ring topology and discuss the possibility of observing an acoustic analogue of quantum superradiance in ultracold atomic gases.
Recent interest and realization of ultracold bosons confined in shell-shaped, or bubble, traps have opened up several directions in the study of Bose-Einstein condensates (BECs) in intrinsically curved geometries. Here, we explore the prospect of using thin spherical shell-shaped BECs as analog gravity simulators of an expanding or contracting curved universe. We study an interacting BEC bubble subject to a temporal quench of the interaction strength. Our theoretical approach, which uses a Bogoliubov treatment following a dimensional reduction of a spherical BEC to the low-energy excitations of a shell-shaped structure, demonstrates how this system serves as a laboratory analog for a positively curved universe having a time-varying scale factor. We investigate spontaneous pair production triggered by quenches associated with exponentially decaying or growing interaction strengths, focusing on the emergence of oscillations in the structure factor---analogous to Sakharov oscillations in the Cosmic Microwave Background angular power spectrum. We quantify the entanglement of the produced pairs via logarithmic negativity, and show how this measure may be extracted from the power spectrum. These findings establish a bridge between quantum information science and early-universe cosmology in a laboratory setting.
Abstract We theoretically propose a ring-shaped, two-dimensional atomic Bose-Einstein condensate as analog model to investigate back-reaction effects during the pre-heating of the early universe. We study the out-of-equilibrium dynamics by which the inflaton field decays by parametrically exciting the vacuum fluctuations that initially populate the matter fields. By working at the level of the truncated Wigner approximation, our numerical simulations show how a signature of back-reaction beyond the semiclassical level is encoded in the effective friction experienced by the analog of the inflaton field, as well as in the spatial de-phasing of its oscillations and in the entanglement between the inflaton and matter fields degrees-of-freedoms.