International Journal of Theoretical Physics最新文献

The paper studies axial gravitational perturbations of the Hayward black hole, a regular geometry that also arises as an effective solution in asymptotically safe gravity. By computing grey-body factors with the 6th-order WKB method and comparing them to predictions based on the quasinormal modes, the correspondence between transmission coefficients and quasinormal spectra is verified. Quantum corrections, parametrized by (gamma), are shown to suppress both the grey-body factors and the absorption cross-section, while the correspondence remains accurate at the percent level for low multipoles and essentially exact for higher ones.

Quantum computers provide exponential computational advantages over classical systems; however, their practical deployment remains constrained by elevated error rates. To tackle decoding challenges in quantum error correction (QEC), we propose the KAT decoder, a hybrid architecture that integrates Kolmogorov-Arnold Networks (KAN) with the Transformer framework for decoding rotated surface codes. Unlike conventional Transformer decoders that use multi-layer perceptrons (MLPs), KAT replaces MLP layers with spline-parameterized KANs, enabling adaptive nonlinear feature optimization and superior modeling of complex error correlations. Experiments demonstrate that KAT achieves thresholds of (mathbf {4.857} varvec{times } textbf{10}^{varvec{-3}}) (circuit-level noise) and (mathbf {0.1594}) (depolarizing noise), reducing logical error rates by 13% and 5% compared to the Minimum Weight Perfect Matching (MWPM) and Feedforward Neural Network (FFNN) decoders. For rotated surface codes with code distances (mathbf {d=3,5,7,9}), KAT mitigates boundary connectivity and noise propagation by leveraging its multi-head attention mechanism to model global spatiotemporal correlations. Meanwhile, under the circuit-level noise model, KAT outperforms the Transformer across code distances (varvec{d=5,7,9,11}). This result underscores KAT’s application potential in quantum error correction and demonstrates the extensive prospects of deep learning techniques in quantum information processing.

The quantum speed-limit (QSL) time of a single superconducting qubit subject to pure dephasing by bistable random telegraph noise (RTN) is examined. Non-Markovianity is quantified using a coherence-based measure, and the unified QSL time for mixed initial states introduced in Phys. Rev. A 98, 042132 (2018) is employed. The results show that the switching rate, coupling strength, and RTN initialization govern the transition between Markovian and non-Markovian dynamics. At equilibrium, memory effects shorten the QSL time via information backflow, whereas under non-equilibrium initializations the dynamics remain Markovian; nevertheless, strong coupling still accelerates the evolution through enhanced dephasing.

This study presents an analytical investigation of the Schrödinger equation modified by the Dunkl derivative, focusing on two distinct potential forms: the Morse potential and the inverse Morse potential. For each case, explicit expressions for the energy spectrum and the associated wavefunctions are derived. The spectral characteristics are graphically illustrated to compare the influence of both potentials on quantum states. The inverse Morse potential, in particular, is examined for its contrasting confinement properties relative to the standard Morse potential. A comparative analysis is conducted within both generalized and classical spatial frameworks. The paper concludes with a discussion on the physical relevance and potential applications of the obtained results in quantum systems governed by such potential landscapes.

The security of Quantum Key Distribution shares a common-theoretic secure secret key that relies based on the quantum physics laws. The physical system in the Quantum Key Distribution is characterized and the deviations presented due to the imperfections in the realistic devices are taken as a main consideration for guaranteeing security proof. The quantum channel in the BB84 protocol helps to send the polarized light pulses and the polarized photon qubits are used to generate secret shared key. For integrating Quantum Key Distribution with BB84 protocol, three steps such as key generation, key sifting and key distillation are used that are responsible for securing communication between two parties. The cyberattacks of the eavesdropper on qubits by transformation are evaluated based on the probability of the errors and the information against perturbation principle is used for identifying the probability of the error occurrences. For generating quantum error correction codes, the 5-qubit stabilizer code is used to protect single logical qubits from the errors. This stabilizer code has an advantages are powerful error correcting capabilities and balancing qubit usage for making efficient codes for quantum computing. In this research article, the security and reliability are taken as a major concern for quantum key distribution. The experiments are performed for identifying effectiveness of the proposed article through different types of analyses. Among all analyses, the proposed model showed the better outcomes of 97.98% fidelity. The efficacy of the Quantum Key Distribution confirmed that the proposed model is efficient for providing security and reliability to the error correction codes.

GSIC POVMs and MUMs serve as generalizations of symmetric informationally complete (SIC) POVMs and mutually unbiased bases (MUBs), respectively. Both GSIC POVMs and MUMs are suitable for linear quantum state tomography. In this work, we investigate the relationship between GSIC POVMs and MUMs by employing mutually unbiased striations (MUSs), and we present simple and conceptually transparent constructions of MUMs from GSIC POVMs, and vice versa. In these constructions, the efficiency parameter of MUMs is shown to be a monotonically increasing function of that of GSIC POVMs, and vice versa. Interestingly, SIC POVMs and MUBs are not only unnecessary but also excluded in certain constructions, underscoring the distinctive relationship between GSIC POVMs and MUMs revealed in this study.

A viable (:fleft(Rright)) gravity model characterized by a sigmoid-type deformation of the Einstein-Hilbert action, aimed at explaining the observed late-time cosmic acceleration without invoking a true cosmological constant is introduced. The model takes the form (:fleft(Rright)=R-mu:{R}_{0}left[frac{1}{{(1+{e}^{-gamma:(frac{R}{{R}_{0}}-1)})}^{delta:}}right]) where µ, R₀, γ and δ are positive constants controlling the amplitude, transition scale, and slope of the modification. The proposed new sigmoid-exponential (:fleft(Rright)) gravity model constructed to achieve a smooth, bounded transition from the Einstein-Hilbert regime at high curvature to an effective dark energy regime at low curvature. Motivated by phase-transition dynamics and inspired by exponential gravity forms arising in string-inspired and Gauss-Bonnet frameworks, the model ensures analytic continuity, avoids curvature singularities, and naturally yields a geometric dark energy density scaling as (:{rho:}_{DE}propto:{a}^{-1}), consistent with late-time acceleration observations. It is verified that it satisfies all key viability conditions: positivity of the first and second derivatives (:({f}_{R}>0,{f}_{RR}>0)) for avoidance of Dolgov–Kawasaki instability, and a stable de Sitter attractor. The model admits a viable scalar-tensor representation with a scalar field whose effective mass depends on the ambient matter density, enabling chameleon screening in high-density environments. We demonstrate compatibility with solar system constraints, the thin-shell condition, the Compton wavelength criterion, and equivalence principle tests. Also performed a detailed phase space and statefinder analysis.

In this paper, we investigate black hole quasinormal modes using an improved matrix method based on non-uniform grid points. By applying the Jordan transformation, the matrix can be decomposed into a relatively simple form. We then compute the quasinormal mode frequencies using the improved matrix method with different node selections, including Gauss-Lobatto nodes, Gauss-Legendre nodes, Chebyshev-Lobatto nodes, and equally spaced nodes. Additionally, we discuss how to apply the matrix method to compute high-frequency quasinormal modes.

Relating to finding possible upper bounds for the probability of error for discriminating between two quantum states, it is well-known that (textrm{tr}(A+B) - textrm{tr}|A-B|le 2, textrm{tr}big (f(A)g(B)big )) holds for every positive-valued matrix monotone function f, where (g(x)=x/f(x)), and all positive definite matrices A and B. In this paper, we study a new class of functions that satisfy the aforementioned inequality. As a consequence, we introduce a new quantum Chernoff bound. In addition, we characterize matrix decreasing functions and establish matrix Powers–Størmer type inequalities for perspective functions.

In this paper, we explore the Friedmann-Robertson-Walker (FRW) cosmological model within the framework of fractal gravity. We examine the behavior of bouncing cosmology, which offers a solution to the issue of non-singularities present in standard Big Bang cosmology. First We analyze the evolution of cosmological parameters as a function of cosmic time to explore the conditions required for the occurrence of a bouncing cosmological model. We reconstruct the bouncing universe through the redshift parameter and introducing the dimensionless parameter (r(z)=frac{H(z)^2}{H_{0}^2}). Constraints are applied using the (chi ^2) test, yielding best-fit values that strongly align with the (Lambda)CDM model. We observed the violation of both the null energy condition and the strong energy condition. Finally, we assess the stability of the model using a function based on sound speed. It is observed that the model remains stable at late times.