Annalen der Physik最新文献

The negatively charged nitrogen-vacancy (NV) center in diamond is a leading solid-state quantum emitter, offering spin-photon interfaces over a wide temperature range with applications from electromagnetic sensing to bioimaging. While NV centers in bulk diamond are well understood, embedding them in nanodiamond (ND) introduces complexities from size, NV location, and NV polarizations. NVs in ND show altered fluorescence properties, including longer lifetimes, lower quantum efficiency, and higher sensitivity to dielectric surroundings, which arise from radiative suppression, surface-induced non-radiative decay, and escape inefficiency at the diamond-background interface. Prior models typically addressed isolated aspects, such as dielectric contrast or surface quenching, without integrating full quantum-optical NV behavior with classical electrodynamics. We present a hybrid framework coupling rigorous electromagnetic simulations with a quantum-optical NV model including phonon sideband dynamics. NV emission is found to depend strongly on ND size, NV position, and surrounding refractive index. Our results explain observations such as shallow NVs in water-coated ND appearing brighter than deeper ones in air. This integrated model provides a unified framework for realistic NV in ND emission scenarios and informs the design of efficient NV-based sensors and quantum devices, advancing understanding of quantum emitter photophysics in nanoscale crystals.

Topologically protected systems are characterized by robust boundary states immune to perturbations. Herein, we propose and analyze a tripartite scheme for simulating topological edge states with silicon-vacancy (SiV) center arrays in 1D phononic crystals. We first investigate the pattern of trimer interactions extended from the standard Su-Schrieffer-Heeger (SSH) model. In momentum space, the results indicate that this structure exhibits unique topological properties, including specific symmetries and multiple types of boundary state configurations. Among them, depending on the hopping integrals, the system harbors both symmetry-protected edge states and topologically trivial edge states. Moving to the realistic quantum system, we introduce a periodic driving protocol for mapping the trimerized spin interactions in 1D phononic crystals (PnCs). Based on the bandgap engineered spin-phonon coupling, after adiabatic elimination of the phonon modes, we derive the highly tunable long-range spin interactions. Thus, by means of a specially designed on-site potential with periodic driving, one can selectively control and enhance the spin-spin interactions, thereby achieving trimerized interaction in SiV center arrays. We show that, the effective Floquet Hamiltonian combines the inversion and time-reversal (TR) symmetries, and then numerically simulate the topologically protected edge states with various periodic driving parameters. This work provides a tunable platform to engineer nontrivial topological states of matter in solid-state quantum systems.

Electromagnetic metamaterials can regulate the propagation behavior of electromagnetic waves through the distribution of effective refractive indices. Two kinds of self-adaptive electromagnetic metamaterials whose electromagnetic properties can be changed automatically under mechanical deformation are designed in this research. When the two kinds of metamaterials undergo bending or shear deformation, respectively, electromagnetic waves propagating in them will also propagate in a bent or sheared path, respectively. The metamaterials are designed to be a combination of an effective electromagnetic medium, which is realized using dielectric arrays, and a mechanical structure, which is realized using a mechanical metamaterial or a link mechanism. The self-adaptive conditions of the two kinds of metamaterials are derived based on transformation optics theory, and the structural parameters of the metamaterials are determined with the help of computer simulation. The self-adaptivity of the metamaterials is verified through full wave simulation. The self-adaptive metamaterials designed in this study are passive with no need for external sensors or power source, and the non-resonant feature of the metamaterial structures enables a broad band operating frequency. This research may be helpful for the future applications of metamaterials in complex environments.

We present our studies on intra-trap dynamics of an optical dipole trap loaded from a Magneto-optical trap of $��{}^{87}�\mathrm{Rb}�$ atoms. A spatio-temporal Monte Carlo simulation approach has been employed in conjunction with the semi-classical theory based calculations for the estimation of various intra-trap two-body loss parameters in the optical dipole trap. Our methodology gives a close estimation of the experimentally observed the atom-number evolution in the optical dipole trap. We also find that, the decay rate of atoms in an optical dipole trap is dominated by momentum-transfer elastic collisions due to the absence of Magneto-optical trap beams. However, in presence of Magneto-optical trap beams, the radiative escape process is the dominant two-body loss mechanism in the trap, which surpasses the fine-structure changing and hyperfine changing collisional losses by nearly an order of magnitude.

In quantum communication, quantum state transfer from one location to another in a quantum network plays a prominent role, where the impact of noise could be crucial. The idea of state transfer can be fruitfully associated with quantum walk on graphs. We investigate the consequences of non-Markovian quantum noises on periodicity and state transfer induced by a discrete-time quantum walk on graphs, governed by the Grover coin operator. Different bipartite graphs, such as the path graph, cycle graph, star graph, and complete bipartite graph, present periodicity and state transfer in a discrete-time quantum walk depending on the topology of the graph. We investigate the effect of quantum non-Markovian dephasing noises, particularly quantum non-Markovian Random Telegraph Noise (RTN) and modified non-Markovian Ornstein-Uhlenbeck Noise (OUN) on state transfer and periodicity. We demonstrate how the RTN and OUN noises allow state transfer and periodicity for a finite number of steps in a quantum walk. Our investigation brings out the feasibility of state transfer in a noisy environment.

Quantum speed limits (QSLs) establish intrinsic bounds on the minimum time required for the evolution of quantum systems. We present a class of QSLs formulated in terms of the two-parameter Sharma–Mittal entropy (SME), applicable to finite-dimensional systems evolving under general nonunitary dynamics. In the single-qubit case, the QSLs for both quantum channels and non-Hermitian dynamics are analyzed in detail. For many-body systems, we explore the role of SME-based bounds in characterizing the reduced dynamics and apply the results to the XXZ spin chain model. These entropy-based QSLs characterize fundamental limits on quantum evolution speeds and may be employed in contexts including entropic uncertainty relations, quantum metrology, coherent control, and quantum sensing.

We review five years of experimental and theoretical attempts (2020–2025) to enhance the superconducting critical temperature (T_c) of hydrogen-rich compounds by alloying binary superhydrides with additional elements. Despite predictions of higher T_c in ternary systems such as La–Y–H, La–Ce–H, and Ca–Mg–H, experiments consistently show that the maximum T_c in disordered ternary superhydrides does not exceed that of the best binary parent hydrides within experimental uncertainty. Instead, alloying primarily stabilizes high-symmetry polyhydride phases at lower pressures, enabling T_c ≈ 200 K near 100–110 GPa, while also strengthening vortex pinning and upper critical fields. Magnetic dopants suppress T_c, whereas nonmagnetic additives leave it nearly unchanged, reminiscent of Anderson's theorem. These findings indicate that alloying is unlikely to raise T_c, but can reduce the pressures required to stabilize high-T_c phases. We propose that fully ordered ternary hydrides, synthesized via controlled hydrogenation of intermetallic precursors, offer a promising route toward this goal. One of the most promising compounds of this kind is the recently discovered LaSc₂H₂₄.