Annalen der Physik最新文献

The statistics of sequential measurements of two non-commuting observables typically depends on the order in which they are measured. However, if a system evolves unitarily between sequential measurements of dichotomic observables (i.e., observables whose measurement outcomes are labeled by $��\pm �1�$), then the expectation value of the product of the sequential measurements is in fact independent of the order of the measurements, provided that one uses the inverse unitary for the opposite order. In this work, a quantum Bayes' rule is used to show that the aforementioned time symmetry for sequential measurements of dichotomic observables extends to open quantum systems that evolve according to a general quantum channel between measurements. Such results are quite striking in light of the standard view that open quantum systems—which may lose information to their environment—are not reversible in any operational sense. An example of such time-symmetric correlations is given for the amplitude-damping channel, where it is observed that the symmetry is realized by a reverse channel that is a combination of the Petz recovery map together with a dephasing channel.

Nanocones

Where the infinitesimal meets the infinite, nanocones of graphene and boron nitride arise as silent analogues of gravitation. Through the lens of the Teleparallel Equivalent of General Relativity, their torsional energies mirror the very fabric of spacetime, hinting that the smallest architectures of matter may unveil the hidden order of the cosmos. More details can be found in the Research Article by F. L. Carneiro and co-workers (DOI: 2400448).

In recent years, the exploration of topological phononic states in 2D materials has become a key research area. This study presents a systematic analysis of the distinctive topological characteristics in the monolayer binary compound InN₂. Within its phononic spectrum, prominent topological band crossings are observed in two optical branches, corresponding to two quadratic nodal points localized at the M and Γ points. A thorough examination of the underlying mechanisms governing band formation and dispersion conditions has been conducted. Notably, the edge states associated with these quadratic nodal points are clearly resolved. These states exhibit two critical properties: they are spatially well-separated from bulk band projections, and they display extensive spatial distributions—attributes that significantly enhance their experimental detectability and practical utility. To further advance the material's application potential, this work also characterizes its mechanical properties, revealing significant anisotropic behavior in key parameters. Collectively, the identification of these ideal topological quadratic nodal point states, combined with the material's inherent stability, provides a robust foundation for future experimental verification. This investigation is poised to accelerate progress in the rapidly developing field of 2D topological materials, offering new insights that may facilitate breakthroughs in phononic device design and topological quantum applications.

Lattice models that exhibit topological zero-energy boundary modes show a remarkable sensitivity to the system length and the applied boundary conditions. The exact solutions for the eigenenergies and band gap of the topological modes in a generalized two-band non-Hermitian model on a topolectrical circuit platform are presented, which show an extra-ordinary dependence on the system size. Additionally, it is shown that the introduction of non-Hermiticity results in the recovery of topological modes with the exact eigenenergy of zero at a certain critical system size. Such zero-admittance edge states are reflected in the large impedance peaks in the impedance spectrum. The results reveal that the boundary modes of a non-Hermitian lattice can be tuned via system size.

In the present theoretical work, magnetic response of a tight-binding (TB) dimerized ring subjected to Aharonov–Bohm (AB) flux and environmental interactions is numerically explored. Specifically, an imaginary site potential on the odd lattice sites is introduced to represent physical gain and loss, while the even lattice sites remain unperturbed. The induced current resulting from the AB flux in both real and imaginary eigenspaces, aiming to enhance this current significantly by adjusting the gain/loss parameter ($�d$) is investigated. The analysis focuses on how exceptional points in the real and imaginary eigenenergy spaces contribute to notable increases in current at specific $�d$ values, and the emergence of purely real current when the imaginary current vanishes. How the dual behavior of energy spectrum (real and imaginary), converging to and diverging from zero energy, affects the enhancement of the current is discussed. Additionally, the interplay between the correlations of dimerized hopping integrals and the gain-loss parameter, which affects the current and highlights key features associated with these physical parameters, is studied. Furthermore, how system size impacts the findings is considered. The study may reveal unconventional characteristics in various loop configurations, potentially paving the way for new research directions.

The electronic transmission properties of two-terminal graphene nanoribbon (GNR) devices, featuring ring and ladder geometries with varying sizes, are investigated to understand the influence of explicit charge doping on their electrostatic control. The results indicate that explicit charge doping affects the device behavior, from single electron transport to resonant transport for different channels. When charge doping is applied, it induces quantum dot formation electrostatically, causing the ladder-type channel GNR with a channel length of 49.7 Å to function similarly to a quantum dot. Therefore, this smallest ladder type channel shows current oscillations which are attributed to single-electron tunneling. As the channel length increases in ladder-type devices, a current path develops within the channel, forming a conductive path in larger devices that results in significant current and eliminates the tunneling barrier effect. On the other hand, for the ring-shaped GNRs, it is found that the transport behavior gradually shifts from an antiresonant to a resonant transport regime with increasing radius under explicit charge doping. These results show a strong competition between quantum-confinement effects and quantum dot-to-electrode coupling for both geometries when explicit charge doping is applied.

This work examines the instantaneous lifetime dynamics of a positronium (Ps) atom under spherical confinement, influenced by a short laser pulse, and embedded in different plasma environments such as plasma-free (PF), Debye plasma (DP), quantum plasma (QP), and nonideal classical plasma (NICP). The effects of medium parameters-particularly the screening length, confinement radius, pulse frequency, and pulse strength are systematically analyzed. For the plasma interactions of the Ps atom, the work considers the screened Coulomb potential, exponential cosine screened Coulomb potential, and nonideal classical plasma potential. The corresponding wave equation is solved numerically using the tridiagonal matrix method. The effects of the short laser pulse are probed within the Runge–Kutta–Fehlberg formalism. Under the influence of the short laser pulse, the screening effects of plasma environments on the instantaneous lifetime of Ps are systematically examined in the time domain, and the functionalities of these environments are compared in detail. A similar analysis is also performed for the spherical confinement radius, as well as the strength and frequency of the short laser pulse. Significant influences and functional dependencies of the medium parameters and laser pulse on the instantaneous lifetime are identified. These results not only contribute to understanding the behavior of the Ps atom in complex environments but also provide a new perspective for controlled positronium applications in experimental plasma systems. The obtained findings offer new possibilities for engineering the lifetime dynamics of short-lived quantum structures, particularly Ps, in the context of laser-matter interactions and precise control of quantum systems in plasma environments. In this regard, they hold significant application potential across a broad spectrum ranging from antimatter physics to quantum optics.

The photonic spin Hall effect (SHE) is explored in a highly tunable Rydberg-based atomic system by leveraging the distinctive properties of Rydberg superatoms. These superatoms arise from strong dipole–dipole interactions and extended radiative lifetimes, resulting in collective excitations governed by the dipole blockade mechanism. An ensemble of three-level atoms in a cascade configuration models a medium in which each superatom acts as a coherent quantum entity. The photonic SHE shows strong dependence on the probe field Rabi frequency and atomic number density. At high Rabi frequencies, the blockade effect suppresses the photonic SHE, confining its occurrence to specific resonant conditions. In contrast, under weak probe excitation, the blockade influence diminishes, enabling an amplified photonic SHE response at resonant detuning due to increased light-matter interaction sensitivity. Reducing atomic number density further broadens the detuning range over which the photonic SHE occurs, indicating a transition toward a more sensitive, less resonance-constrained optical behavior. The effect of van der Waals interactions on the photonic SHE shift is also characterized. This expanded operational bandwidth demonstrates the potential of Rydberg-based systems for robust spin-optical control, particularly in scenarios where precise stabilization of the probe field frequency is experimentally challenging.