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Collective multipartite Einstein-Podolsky-Rosen (EPR) steering is a type of quantum correlation shared among $n$ parties, where the EPR paradox of one party can be realized only by performing local measurements on all the remaining $n\ensuremath{-}1$ parties. Here, we propose an efficient method to produce collective multipartite EPR steering via symmetrically and asymmetrically cascading parametric amplification processes, i.e., four-wave mixing (FWM) of rubidium atoms. The simplified collective-steering criterion is introduced using the Coffman-Kundu-Wootters monogamy relation. Moreover, by actively adjusting the parametric gains, the collective EPR steerability is optimized in our schemes. We find that the scale of collective steering can be extended by cascading more FWMs; in particular, introducing optical loss is useful for generating collective steering with more parties only in the asymmetry structure. Our results pave the way for the construction of quantum networks and provide a promising candidate for one-sided device-independent quantum cryptography among multiple users.

The experimentally verified negative Poisson's ratio of black phosphorus allows the extension of the medical and defense applications to the nanoscale regime without any artificial engineering. With a structure analogous to monolayer black phosphorus, monolayer SiS, SiSe, SnTe, and W-phase antimonene are predicted to show auxetic behavior, while a W-phase antimonene does not by using first-principles calculations. By putting these systems into a collective perspective with other puckered two-dimensional (2D) materials, we further formulate a uniform mechanism that could explain the different types of out-of-plane Poisson's ratio in the puckered 2D materials including monolayer group V-enes (BP, As, and Sb) and group IV monochalcogenides (SiS, SiSe, GeS, GeSe, SnS, SnSe, and SnTe). We found that both the structure and composition of the puckered monolayers play important roles in the out-of-plane Poisson's ratio.

Multimode quantum correlation has important applications in the field of quantum information. In this paper, we propose a compact scheme to generate multiple quantum correlated beams based on energy-level cascaded four-wave mixing (EC-FWM) process in a single atomic medium of rubidium. Injecting two strong pump beams with different frequencies and one weak probe beam into one rubidium vapor, four possible parametrically amplified FWM (PA FWM) processes can coexist under different phase matching conditions. Within the scheme, the weak probe beam is amplified and three coherent beams are generated, which can also be seen as an eight-wave mixing (EWM) process when certain phase matching condition is satisfied. Based on the energy level system of the scheme, three different cascaded structure models are employed to study the quantum correlation between the four generated beams. Amplitude and phase quadratures squeezing and intensity squeezing of the three- and four-mode are calculated via the input–output relations of the system. We found versatile multimode squeezing can be generated in all the structures, but the degree of squeezing and its distribution among the modes are different, depending on the specific structure. Furthermore, the relation of the quantum correlation, as well as the eigenmodes and eigenvalues of the four-mode quantum states are studied.

This study demonstrated a generic and simple approach to generate durable antibacterial ability on cellulose without using covalently bonding tethering groups that limit the structure design. CO2-philic silicone with quaternary ammonium salt (QAS) pendants was synthesized through hydrosilylation reaction of poly(methylhydrosiloxane) (PMHS) and 2-(dimethylamino)ethyl acrylate in the presence of platinum-based catalyst and subsequent quaternization with 1-bromohexane. The resultant QAS silicone was deposited onto cellulose by adsorption from supercritical CO2 (scCO2) to provide potent biocidal activities against Staphylococcus aureus and Escherichia coli. Presented data also showed that the antibacterial layer was very stable toward washing and UV irradiation owning to the low surface tension and relatively high bond energy of the backbone of silicone. This procedure is applicable to substrates of other shape and chemistry.