Annalen der Physik最新文献

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.

This paper proposes a novel approach to controlling the amplitude of the Aharonov–Bohm effect by utilizing a conformal mapping-based method. The core idea is to leverage the form-invariance of the Schrödinger equation under conformal transformations, which allows for the manipulation of the scattering amplitude through a carefully designed scalar potential. This approach extends the concept of transformation physics into charge-flux systems, providing a practical means to steer matter waves influenced by magnetic flux interactions. The paper comprehensively discusses how scalar potentials, determined by conformal mappings, can counterbalance the Aharonov–Bohm scattering, thus offering a new avenue for quantum control by local means rather than purely through non-local flux interactions.

The pursuit of room-temperature superconductivity has increasingly focused on hydrogen-rich compounds, where high-frequency hydrogen vibrations foster strong electron–phonon coupling, and dense crystalline phases under high pressure enable exceptional electronic properties. While binary hydrides such as H₃S and LaH₁₀ represent landmark successes, recent evidence suggests that ternary hydrides can achieve high-temperature superconductivity at substantially lower pressures, often with enhanced stability. Motivated by this potential, we perform a systematic computational screening of ternary hydrides. By integrating statistical insights from superconducting databases with empirical design principles based on hydrogen content, atomic mass ratio, and electronegativity, we efficiently navigate a vast chemical space. From an initial set of 261,532 A-B-H compositions, our algorithm identifies 3,453 candidates satisfying optimal descriptors criteria. This set includes 56 known superconductors, thereby validating the method, and 3,397 novel predictions. A subsequent refinement based on chemical feasibility narrows the list to 543 high-priority novel candidates with the greatest potential for high-T_c superconductivity. Notably, several compositions from our predicted set, including MgZrH₁₂, LuCaH₁₂, and BCaH₈, have been independently confirmed by recent first-principles calculations, underscoring the predictive power of our approach.

Systematic evaluation of spin orbit coupling on models for cubic LaH₁₀ (SG: $��F�m�\overline{3}�m�$) at pressure is based on ab initio density functional theory calculations with optimized experimental cell dimensions. Primitive lattice LaH₁₀ band structure details show asymmetric cosine-shaped bands that link key lattice nodes and cross the Fermi level. Crystal orbital overlap populations show that H─H bonds in the cubic unit cell contribute to bonding–antibonding transitions evident in cosine-shaped bands along the Γ–X reciprocal direction. Measures of energy asymmetry for these cosine-shaped bands reveal matches of calculated T_c with experimental T_c values for cubic LaH₁₀ at pressures between 135 and ∼220 GPa. Electron density distributions associated with asymmetry of the LaH₁₀ irregular chamfered cube are attributed to variations in hydrogen bonding with pressure. Changes to lattice vibrations between 135 and 220 GPa are co-incident with experimental and theoretical evidence for structural transformations at these pressures. Collective behaviour of hydrogen lattice vibrations and asymmetric changes to crystal structure are consistent with the dome-like format for experimental T_c values with pressure.

This work presents a novel traversable wormhole solution within the modified gravity framework of $��f�(�R�,�L�,�T�)�$ theory, where the gravitational action non-minimally couples geometry and matter fields. Employing the Van der Waals equation of state to model the exotic matter sustaining the wormhole throat, the field equations are analytically and numerically solved under a constant redshift function assumption. The shape function obtained satisfies all key wormhole conditions: throat regularity, flaring-out, and asymptotic flatness. Detailed energy condition analyses reveal global violation of the null energy condition by matter, though the modified gravity coupling permits shifting exotic behavior into the geometric sector. Stability is assessed via the volume integral quantifier, speed of sound, and adiabatic index, indicating a physically plausible, stable wormhole structure supported by anisotropic pressures. This study elucidates how tunable matter-geometry couplings in $��f�(�R�,�L�,�T�)�$ gravity can minimize exotic matter requirements and offers pathways for potential astrophysical signatures of such wormholes.