Annalen der Physik最新文献

The quasiparticle spectrum and transport properties of the double quantum dot (DQD) deposited on a superconducting substrate (Andreev molecule) and side-coupled to a nanowire hosting Majorana zero modes (MZMs) are studied. Placing a DQD on the superconducting substrate induces the trivial Andreev-bound states (ABSs) in quantum dots. However, coupling of DQD with a nanowire causes the leakage of the MZM from the topological nanowire into quantum dots. The relationship between the Andreev states and the Majorana mode for different values of the coupling parameters is analyzed. Additionally, it is shown that the connection point of a metallic tip, treated as an scanning tunneling microscope (STM) tip, affects the measured results of the differential conductance.

Matrix-Product State Approach

The atomic nucleus contains particles that form interacting pairs, mirroring the Cooper pairs observed in superconductors. These pairs are traditionally analyzed using the mean-field technique pioneered by Bardeen, Cooper, and Schrieffer (BCS). However, the matrix-product state (MPS) approach, originally developed for one-dimensional spin chains in condensed-matter physics, offers a significant advancement. This method enables the precise computation of nuclear properties from both simple and more generalized pairing Hamiltonians, eliminating the artifacts commonly associated with mean-field approximations. For further details, see article number 2300436 by Roman Rausch and co-workers.

In this work, a scheme to protect quantum entanglement from a non-Markovian noisy environment is proposed. By applying two quantum weak measurements before and after sending the quantum state into the noisy channel, the quantum state can be “pushed” closer to a decoherence-free state, reducing decoherence during the time evolution. Then, the second weak measurement can partially retrieve the initial quantum state from the state corrupted by the noisy environment. The study involves a non-Markovian dynamic equation to examine the impact of the memory effect on the protection scheme's performance. Various factors affecting the residual entanglement and the success probability are analyzed. The results suggest that two measurement strengths shall be chosen approximately in a linear relation, with the best ratio determined by the memory time of the environment. Additionally, it is demonstrated that the memory effect significantly enhances the protection efficiency. Lastly, the scheme's robustness against systematic errors is evaluated. 

Despite the extensive applications of perovskite compounds, the precise nature of non-Hermitian bonding in these materials remains poorly understood. In this study, density functional theory calculations are performed to determine the electronic structures of perovskite compounds. In particular, the bandgaps of Ba₂ScNbO₆ and Ba₂LuNbO₆ are found to be 2.617 and 2.629 eV, respectively, and the deformation bond energies and non-Hermitian bonding of these compounds are calculated. The relationship between the non-Hermitian zeros of the O-Nb bond of Ba₂ScNbO₆ and the non-Hermitian zeros of the Sc-O bond is found to be similar but with varying sizes. Further, in-depth research on non-Hermitian chemistry verified that precise control of atomic bonding and electron states can be achieved, providing new insights into the study of chemical bonds.

Quantitative climate mobility research has, so far, focused primarily on climate change impacts on migration outcomes. This focus has led to a separation between quantitative climate migration research and the broader field of migration studies. In this paper ways are proposed for quantitative research to better address the complexity in the relationship between climate change and mobility. First technical suggestions are presented to improve upon migration model setups and designs and highlight promising developments. Then it is argued that quantitative methodologies can broaden the scope of research inquiries by examining how climate mitigation and adaptation efforts influence mobility, as well as assessing how mobility itself impacts vulnerability.

In the realm weak force sensing, an important issue is to suppress fundamental noise (quantum noise and thermal noise), as they limit the accuracy of force measurement. In this study, a weak force sensing scheme that combines a degenerate optical parametric amplifier (OPA) and an auxiliary mechanical oscillator into a cavity optomechanical system to reduce quantum noise is investigated. It is demonstrated that the noise reduction of two coupled oscillators depends on their norm mode splitting. and provide a classic analogy and quantum perspective for further clarification. Besides, the noise reduction mechanism of OPA is to reduce the fluctuation of photon number and enhance the squeezing of the cavity field. A specific design is proposed that aimed at enhancing the joint effect of both, beyond what can be achieved using OPA alone or two series coupled oscillators. This scheme provides a new perspective for deeper understanding of cavity field squeezing and auxiliary oscillator in force sensing.

High-field superconductors are characterized by a spin splitting of the density of states, giving rise to spin transport phenomena. This includes spin-polarized tunneling, spin-dependent thermoelectric effects, long-range quasiparticle spin transport, and spin-dependent coupling of supercurrents and quasiparticles. This review gives a brief overview of the theory background, recent experimental progress in the field, and an outlook on open problems and possible applications.

The additivity properties for both bipartite and multipartite systems are investigated by using entropic uncertainty relations (EUR) defined in terms of the joint Shannon entropy of probabilities of local measurement outcomes. In particular, state-independent and state-dependent entropic inequalities are introduced. Interestingly, the violation of these inequalities is strictly connected with the presence of quantum correlations. It is shown that the additivity of EUR holds only for EUR that involve two observables, while this is not the case for inequalities that consider more than two observables or the addition of the von Neumann entropy of a subsystem. They are applied to bipartite systems and to several classes of states of a three-qubit system.

Feature dimensionality plays an important role for modern medical diagnosis and image processing. In this work, the study introduces an optoelectronic neural network for multimodal image segmentation, which dramatically improves computing speed and decreases imaging acquisition cost in brain tumor diagnostics. Multi-layer metasurfaces are utilized as an image preprocessor that reduces image dimensionality at the physical layer. The low-dimensional image is then processed to a U-Net semantic segmentation network, to handle the complex and heterogeneous nature of brain image data. By using diffractive neural network, the metasurface encoder is optimized and physically constructed with high-efficiency transmission metasurfaces. The entire optoelectronic network attains a structural similarity index measure (SSIM) of 96%, demonstrating its potential to revolutionize on-site medical image processing with its high precision in segmenting brain imaging data.