Motivated by the significantly improved scalability of optically trapped neutral-atom systems, extensive efforts have been devoted in recent years to quantum-state engineering in Rydberg-atom ensembles. Here we investigate the problem of engineering generalized (``twisted'')
W states, as well as Greenberger-Horne-Zeilinger (GHZ) states, in the strongly interacting regime of a neutral-atom system. We assume that each atom in the envisioned system initially resides in its ground state and is subject to several external laser pulses that are close to being resonant with the same internal atomic transition. In particular, in the special case of a three-atom system (Rydberg-atom trimer) we determine configurations of field alignments and atomic positions that enable the realization of chiral
W states---a special type of twisted three-qubit
W states of interest for implementing noiseless-subsystem qubit encoding. Using chiral
W states as an example we also address the problem of deterministically converting twisted
W states into their GHZ counterparts in the same three-atom system, thus significantly generalizing recent works that involve only ordinary
W states. We show that starting from twisted---rather than ordinary---
W states is equivalent to renormalizing downward the relevant Rabi frequencies. While this leads to somewhat longer state-conversion times, we also demonstrate that those times are at least two orders of magnitude shorter than typical lifetimes of relevant Rydberg states.
We present a theoretical scheme for generating vortex light bullets (LBs) in a Rydberg atomic system. The stability property and propagation dynamics of vortex LBs with different topological charges are investigated in twisted circular waveguide arrays with a parity-time (
PT) symmetry. The numerical solutions of the corresponding nonlinear Schr\"odinger equation are obtained by the modified square operator method and split-step Fourier method. The longitudinal twist changes the stabilities of six-core vortex LBs and enriches the modulation diversity as the states with the opposite charges degenerate by the introducing of rotation frequency. Specifically, we reveal that the energy exchange between waveguides and media gives rise to the formation of necklace breathers, which is crucial for implementing light storage. These unique characteristics arise from the balance or quasibalance among the rotation frequency, the Rydberg-Rydberg interaction, and the nonequivalent gain/loss distribution along the azimuthal direction. We thus provide examples of robust high-charge vortex LBs and necklace breathers in the Rydberg atomic system with a
PT symmetry.