Abstract Quantum steering, also know as Einstein–Podolsky–Rosen steering, is a key resource in quantum information. It has significant application value for constructing secure quantum communication networks due to its unique asymmetric property. However, quantum steering is susceptible to decoherence. Decoherence occurs due to the interaction between a quantum system and its environment, and eventually leads to the reduction or even disappearance of steering. In this paper, we propose an all-optical correlated noise channel (ACNC) scheme based on four-wave mixing (FWM) processes, investigate the impact of noise in the channel and FWM gains on quantum steering characteristics as well as the capability of the ACNC to restore quantum steering. This scheme is achieved through optical nonlinear processes and avoids the electro-optic conversions and significantly expands the operational bandwidth. The research results show that the ACNC can effectively restore the damaged quantum steering. The range of one-way steering and genuine tripartite steering can be flexibly controlled by adjusting parameters. Moreover, the Gaussian steered monogamous relationships have also been verified. Our scheme provides new theoretical reference for constructing all-optical secure quantum networks.

Abstract The effect of the generalised exponential cosine screened Coulomb potential (GEC-SCP) on the stability of a model two-electron atom (Ze+e+e) interacting via this type of potential has been investigated. GECSCP is taken in the form: V(ρ: μ,θ) = exp[-(μ cosθ)ρ] cos(μ sinθ)ρ]/ρ (in a.u.), where µ (0 ≤ µ < ∞) and θ (0 ≤ θ ≤ π/2) are two adjustable parameters. An extensive wavefunction, having 715 number of terms, is utilised to calculate the ground state energy of the model atom (for Z = 1, 2, 3) within the framework of the Ritz's variational method. Convergence of the computed results with respect to the number of terms in the wavefunction is corroborated. An inclusive study is made on the variation of the ground state energy and other related quantities with respect to the parameters µ and θ. Special emphasis is given on the determination of the critical values of the parameters which correspond to the critical bound-continuum limits of the model atoms.

Abstract This paper aims to substantially enhance the entanglement of the two-mode squeezed vacuum state (TMSVS) by proposing a new state engineered through a sequential application of a state-projective operation followed by a phase measurement. This construction exploits a laser field modeled as a coherent state of moderately strong amplitude, thereby compensating for the limited squeezing achievable in practice. Remarkably, the resulting state achieves entanglement, quantified by the von Neumann entropy, exceeding 3.45 even for moderate squeezing ($r \leq 0.6$), whereas it remains below 1.22 for the TMSVS. In addition, we show that the state can teleport a coherent state with an average fidelity exceeding 99\%. Finally, we propose an optical scheme for generating the new state. In addition to the phase measurement element, the scheme employs three weak cross-Kerr nonlinear media, two beam splitters, and a nonideal on-off photodetector. The proposed state can be utilized for quantum information processing, particularly in continuous-variable quantum circuits involving entanglement.

Abstract We present a self-adaptive stochastic basis strategy within the Schwinger Variational Principle (SVP) framework for low-energy positron-atom scattering. The method constructs compact, system tailored basis sets using uncorrelated Slater-type orbitals selected via rejection sampling, guided by physical coupling strengths. This correlation-free approach efficiently captures essential scattering dynamics, both short-and long-range, without the need for explicit electron-positron correlation terms. As a benchmark, we apply the method to positron-hydrogen collisions and compute the s-wave scattering length and zero-energy annihilation parameter, obtaining A = -2.0959(7) and Z eff = 8.576(3), in excellent agreement with high-precision literature values. Extensive convergence and statistical analyses confirm the method's accuracy, robustness, and fast convergence. The generality and low computational cost of the approach make it a promising tool for high-precision scattering calculations in atomic and molecular systems.

Abstract We present a detailed comparison of theoretical approaches for modeling strong-field ionization by few-cycle laser pulses. The dipole approximation is shown to accurately capture interference structures in photoelectron spectra, while non-dipole effects introduce significant momentum shifts along the propagation direction. Two complementary analytical methods are used: the Jacobi-Anger expansion provides complete spectral decomposition of transition amplitudes, whereas the saddle-point method efficiently identifies dominant ionization pathways. Through this comparative study within the strong-field approximation framework, we establish validity conditions and practical advantages for each approach. Our results provide guidelines for selecting theoretical methods for advancing the interpretation of strong-field processes. These findings provide a roadmap for interpreting strong-field ionization spectra and momentum distributions, highlighting where non-dipole effects and method choice critically alter predictions.

Abstract In this paper, we propose a simple variational ansatz, Ψ ( r 1 → , r 2 → ) = C sin ⁡ ( π r 1 r c ) r 1 sin ⁡ ( π r 2 r c ) r 2 exp ⁡ ( − Z ( r 1 + r 2 ) ) [ cosh ⁡ ( a r 1 ) + cosh ⁡ ( a r 2 ) ] [ 1 + 0.5 r 12 exp ⁡ ( − b r 12 ) ] , to study confined two-electron atomic systems. Here, r 12 = | r → 1 − r → 2 | is the inter-electronic distance with the electron coordinates r → 1 and r → 2 , r c is the radius of the impenetrable well in which the two-electron atoms are confined, and C is the normalization constant. The function sin ⁡ ( π r / r c ) / r incorporates the Dirichlet boundary conditions at r = r c needed for the wave function of two-electron systems, and a and b are the variational parameters evaluated by minimizing the total energy functional of confined two-electron atoms. We also calculate the pressure and check the satisfaction of the virial relation for such systems. Our results for the ground-state energy and its components, radial distance moments, and pressure show agreement with the existing literature.

Abstract This work studies the non-equilibrium dynamics of polarized fermions in a one-dimensional cavity-assisted hopping lattice with an incommensurate potential. By employing the Keldysh Green’s function method to solve the equations of motions, we demonstrate that both the superradiance and kinetic energy of the atoms are suppressed, if we tune the strength of the incommensurate potential large enough. We also find that the right directed current originates from the skin effect, which is derived by two processes: one is the superradiance; another is the energy pumping of the oscillating phase of the cavity mode. Besides these, we explore the other dynamical properties associated with different boundary conditions and prove the unique characteristics of the steady state in our model.