Science China Physics, Mechanics & Astronomy最新文献

Long-distance entanglement distribution is fundamental to the establishment of a large-scale quantum network, particularly in systems that operate without the need for trusted relays. Here, we demonstrate entanglement-based quantum key distribution over 343 km of fiber spools using multi-wavelength single-photon-level calibration light for reference frame alignment. By co-propagating calibration and entangled photons through identical paths and sharing detectors in a time-multiplexed manner, a polarization purity of 2783 achieves for two mutually unbiased bases. The system operates continuously for 27.1 h in the laboratory, generating a total of 253 bits secure key at an asymptotic secure key rate of 3.68 × 10⁻³ bps. This work provides a viable approach for constructing large-scale quantum network.

Organic micro-nanophotonics is an emerging interdisciplinary field that integrates photonics, nanoscience, and materials chemistry to explore light-matter interactions at the nanoscale. Compared with inorganic counterparts, organic materials offer distinct advantages such as high photoluminescence efficiency, tunable optical properties, and facile processability, which enable flexible and multifunctional nanophotonic applications. This review summarizes recent advances in organic nanophotonic materials and their applications in integrated photonic devices. First, we highlight the unique photophysical characteristics of typical organic materials—including small molecules, conjugated polymers, and hybrid systems—emphasizing their structural versatility and excited-state dynamics. Next, we discuss representative organic photonic devices such as lasers, photodetectors, OLEDs, photovoltaics, modulators, and optical coding systems, focusing on how organic components enhance device functionality. We further review recent progress in the design and fabrication of integrated organic photonic platforms, including patterning techniques, photonic integrated circuits (PICs), and nonlinear photonic systems. Finally, we outline the remaining challenges in the field and provide perspectives on future research directions, particularly in the rational molecular design and structure-property relationship of organic materials. By offering a comprehensive overview, this review aims to promote innovation in the development of tunable, high-performance nanophotonic devices based on organic materials.

The recent discovery of high-T_c superconductivity in Ruddlesden-Popper (RP) nickelates has motivated extensive efforts to explore higher-T_c superconductors. Here, we systematically investigate Nd-doped La₃Ni₂O₇ using density functional theory (DFT) and renormalized mean-field theory (RMFT). DFT calculations reveal that both the lattice constants and interlayer spacing decrease upon Nd substitution, similar to the effect of physical pressure. However, the in-plane Ni-O-Ni bond angle evolves non-monotonically with doping, increasing to a maximum at 70% (∼2/3) Nd doping level and then falling sharply at 80%, which leads to a reduction in orbital overlap. Moreover, Nd doping has a more pronounced effect on the Ni-(d_{z^{2}}) orbital, demonstrating an orbital-dependent effect of rare-earth substitution. Through the bilayer two-orbital t-J model, RMFT analysis further shows an s_±-wave pairing symmetry, with T_c rising to a maximum at about 70% Nd substitution before declining, in agreement with the transport measurements. The variation in T_c can be traced to the competition between continuously enhanced interlayer (d_{z^{2}}) orbital hopping and a gradual decrease in electron density. These results highlight the delicate interplay among structural tuning, orbital hybridization, and superconductivity, providing important clues to design higher-T_c RP nickelate superconductors.

We propose a scheme to simultaneously achieve nonreciprocal unconventional and conventional photon blockade in a single photonic resonator based on the joint of chiral cavity-atom coupling and parametric amplification, which significantly enhances the nonreciprocal photon blockade (NPB) and is termed universal NPB. We demonstrate that the nonreciprocal unconventional photon blockade dominates in weak coupling regime characterized by chiral and backscattering couplings smaller than decay rate when driving the device from one side but not from the other side, whereas the nonreciprocal unconventional and conventional photon blockades simultaneously account for the NPB in the strong coupling regime. This broadens the parameter space of realizing the NPB and demonstrates a stronger NPB in the strong coupling regime. Furthermore, the nonreciprocity can be improved by approximately three orders of magnitude due to the presence of the parametric amplification. Our findings pave the way for the development of quantum nonreciprocal devices, with potential applications in quantum information processing and chiral networks.

Bulk-boundary correspondence is crucial for understanding topological insulators, as it indicates that nontrivial bulk topology can be revealed from the boundary response. However, not all topological insulators exhibit conventional energy or frequency boundary responses despite possessing a nontrivial bulk topology, which challenges the experimental probing of bulk topology. In this work, we utilize the entanglement spectrum, rather than the energy or frequency spectrum, for experimentally probing the bulk topology. We verify the bulk-entanglement spectrum correspondence in an acoustic multipole topological insulator even without the frequency boundary response. Our work provides a novel paradigm for probing the bulk topology and opens new avenues for exploring topological materials.

By employing the replica trick, we study the impact of the replica parameter n on the modular entropy and the capacity of entanglement in the End of the World (EoW) model and the island model, respectively. For the EoW model, we present n-dependent evolution curves of the modular entropy and the capacity of entanglement under both microcanonical and canonical ensembles. In particular, in the canonical ensemble, all quantities decrease as n increases at late times. For the island model, we develop the replica geometry for finite n and re-evaluate the modular entropy and the capacity of entanglement in a two-sided eternal Jackiw-Teitelboim black hole coupled with a thermal bath. In the case of a single island configuration, the modular entropy and capacity of entanglement closely resemble the thermal entropy and the heat capacity, respectively, yielding results analogous to those obtained in the canonical ensemble for the EoW model. The analysis of the results from these two models strongly indicates that in geometries with a greater number of n copies, more connected geometries effectively purify thermal Hawking radiation. In addition, we compare these findings with statistical mechanics and provide an interpretation for the replica parameter n. Finally, we generalize the island formula to accommodate the finite n case under this interpretation.