Real-imaginary spectrum decomposition of the transparency spectra in microwave dressed Rydberg systems.

To distinguish the contributions of electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) in their applications in precision laser spectroscopy, we propose a real-imaginary spectrum decomposition method to investigate the transparency spectra in a four-level microwave (MW) dressed Rydberg system. We show that the opening transparency windows in the absorption spectra of probe field is a prominent character by EIT, EIT-ATS crossover, and ATS when the MW field is turned off and the intensity of the control field is adjusted. When the MW field is turned on and gradually increased, the EIT is destroyed and disappears. In addition, the most prominent characters that open a transparency window are the EIT-ATS crossover and the ATS. Then, if we further increase the intensity of the MW field, we find that the transparency windows open mainly due to the ATS. Compared to the previous considerations of this issue, which were limited to three-level systems, our four-level scheme reported here is useful for understanding the features of quantum interference in multilevel atomic systems, and has potential applications to study enhanced sensitivity, measurement spectroscopic, quantum processing, quantum communication, and transmission.

Soliton molecules and their scattering by a localized P T-symmetric potential in atomic gases.

We propose a physical scheme to study the formation of optical soliton molecules (SMs), consisting of two solitons bound together with a π-phase difference, and the scattering of SMs by a localized parity-time (P T)-symmetric potential. In order to stabilize SMs, we apply an additional space-dependent magnetic field to introduce a harmonic trapping potential for the two solitons and balance the repulse interaction induced by the π-phase difference between them. On the other hand, a localized complex optical potential obeying P T symmetry can be created through an incoherent pumping and spatial modulation of the control laser field. We investigate the scattering of optical SMs by the localized P T-symmetric potential, which exhibits evident asymmetric behavior and can be actively controlled by changing the incident velocity of SMs. Moreover, the P T symmetry of the localized potential, together with the interaction between two solitons of the SM, can also have a significant effect on the SM scattering behavior. The results presented here may be useful for understanding the unique properties of SMs and have potential applications in optical information processing and transmission.

Selection and cloning of periodic optical patterns with a cold Rydberg atomic gas.

We show that periodic optical patterns formed in a cold Rydberg atomic gas via electromagnetically induced transparency (EIT) can be selected by using a weakly modulated control laser field. We also show that the (hexagonal, stripe, square, etc.) patterns prepared in one probe laser field can be cloned onto another one with high fidelity via a double EIT.

Matter-wave dromions in a disk-shaped dipolar Bose-Einstein condensate with the Lee-Huang-Yang correction.

We investigate, both analytically and numerically, the nonlinear dynamics of (2+1)-dimensional [(2+1)D] matter waves excited in a disk-shaped dipolar Bose-Einstein condensate (BEC) when quantum fluctuations described by the Lee-Huang-Yang (LHY) correction are taken into consideration. By using a method of multiple scales, we derive Davey-Stewartson I equations that govern the nonlinear evolution of matter-wave envelopes. We demonstrate that the system supports (2+1)D matter-wave dromions, which are superpositions of a short-wavelength excitation and a long-wavelength mean flow. We found that the stability of the matter-wave dromions can be enhanced by the LHY correction. We also found that such dromions display interesting behaviors of collision, reflection, and transmission when they interact with each other and are scattered by obstacles. The results reported here are useful not only for improving the understanding on the physical property of the quantum fluctuations in BECs, but also for possible experimental findings of new nonlinear localized excitations in systems with long-ranged interactions.