Optical Memory and Neural Networks最新文献

Abstract

We report on magnetron deposition of thin superconducting rhenium films on sapphire substrates. During the deposition, substrates were held at ambient temperature. Critical temperature of the films is T_c ~ 3.6 K. Films have polycrystalline structure, and grazing incidence X-ray diffractometry indicates that crystalline lattice parameters are somewhat larger compared to the bulk ones. Magnetoresistive and AC/DC susceptibilities allowed us to determine H_c1 and H_c2 of these films, as well as estimate coherence length ξ(0) and magnetic penetration depth λ_L(0). We also provide information on surface morphology of these films.

Abstract

Spin-projection noise sets a limit for the sensitivity of spin-based magnetometers and experiments searching for parity- and time-reversal-invariance-violating dipole moments. The limit is described by a simple equation that appears to have universal applicability.

Abstract

We study the spreading of an initially localized wave packet of a particle hopping on a one-dimensional superlattice during a cycle of a topological Thouless pump. Two contributions to the dispersion of the adiabatic pumping process are identified: a dynamical part and a geometrical part. The magnitude of the dynamical contribution to the spreading depends on the dispersion of the adiabatic transfer state and the cycle time. Unlike the dynamical one, the geometrical contribution does not depend on the duration of the adiabatic process and can be made much smaller than the lattice spacing. We show that as the adiabaticity is enhanced by prolonging the period of the pumping process, the uncertainty in coordinate space is increased linearly with the adiabaticity parameter. We propose a mechanism to smoothen the energy surface of the adiabatic transfer state to reduce the spreading of the spatial distribution of the transported particle. This diminishes or even eliminates (up to the geometric contribution) the dispersion of the coordinate during the transport process.

Abstract

We consider adiabatic interaction of quantum systems with electromagnetic field in the presence of various dissipation processes. As it is known that in the presence of large intermediate detunings any n-level system can be reduced to an effective two-level system, we chose the two-level model as the basic model for a detailed analytical study. We demonstrate the possibility of reducing losses due to dephasing and non-adiabatic corrections by choosing an appropriate design of time-dependent interaction parameters. Simple analytical expressions are derived for both cold and hot atomic ensembles. The results obtained for the two-level system are applied to a three-level system by using the method of adiabatic elimination. Efficient population transfer is shown despite the relatively high dephasing rates.

Abstract

In this paper, we propose the design of detection pixels for single-photon detectors, consisting of absorber and heat sink (Bi-2223), thermoelectric sensors (CeB₆), and an antireflection layer (SiO₂) located on a dielectric substrate (Al₂O₃). We employ modeling and simulation to study the heat propagation processes in multi-layer detection pixels following the absorption of photons with energy ranging from 0.8 eV to 1 keV. Calculations are performed using the heat transfer equation within a limited volume, employing the three-dimensional matrix method. We calculate the temperature temporal variation in different areas of the detection pixels, as well as the voltage generated on the sensor, for various thicknesses and surfaces of the detection pixel layers. We determine the maximum signal value, time at which the maximum signal is reached, signal decay time, and the detector’s count rate. We derive equations for Phonon and Johnson noise in the three-layer detection pixel and calculate the total noise. Based on the data obtained, we propose ways to improve the signal-to-noise ratio.

Abstract

An analytical model of a pair-interacting electron gas localized in an asymmetric biconvex strongly oblate lens-shaped GaAs quantum dot has been considered. The wave functions and the energy spectrum of the system have been calculated in the frame of the exactly solvable two-dimensional Moshinsky model. The character of long-wavelength transitions between the center of mass levels of the system have been obtained when the generalized Kohn’s theorem is realized.

Abstract

In this article has been achieved that the utilization of quantum programmable logic elements opens new possibilities in cryptography, where the ability to process information irreversibly contributes to enhanced security measures. Furthermore, the development of such elements fosters the advancement of complex computational architectures, facilitating the creation of sophisticated and highly efficient systems.

We experimentally demonstrated that dielectrophoretic (DEP) forces of alternating photovoltaic fields generated near the surface of a photorefractive Fe-doped lithium niobate crystal by an optical Bessel beam with concentric ring structure and 532 nm wavelength exert the structuring of pure glycerin layer on the crystal surface and formation of stationary fluid concentric ring pattern. Taking into account this effect, the manipulation and trapping of the Ag nanoparticles suspended in the thin glycerin layer on the crystal surface with Bessel beam-induced photovoltaic field pattern have been studied. The formation of the clusters of Ag nanoparticles is observed. The localization of the Ag particles on the extremes of fluid lattice rings is detected. The trapping process can be described by a two-stage scenario. In the early stage, the stratification of glycerin thin layer under positive DEP force and localization of the fluid in the maxima of the photovoltaic field take place, thus forming the concentric ring fluid channels on the crystal surface. The flow of viscose glycerin in the radial directions also carries along the Ag nanoparticles. In the advanced stage, the repulsive DEP forces lead to the trapping of Ag particles on the crystal surface at the borderlines of fluid lattice rings. The generated photovoltaic space charge fields are long-living and, as a consequence, the formed patterns remain stable for a long time due to the high resistance of the crystal. The photovoltaic tweezers operating in an autonomous regime and allowing the trapping, manipulation and separation of micro-/nanoparticles are promising for photonics, integrated optics, nanoelectronics and biotechnology.

Abstract

2023 is the year of commemoration of M.L. Ter-Mikayelian, a scientist who had important contribution to high energy physics, coherent bremsstrahlung, quantum and nonlinear optics, quantum electronics and laser physics, high-temperature superconductivity, and related fields. This article is scientific biography of the outstanding scientist. The range of scientific interests of M.L. Ter-Mikaelyan was really wide. In this issue, we tried to collect the works of his students and followers.

Abstract

Magnetically induced (MI) transitions F_g = 1 → F_e = 3 of ⁸⁷Rb D₂ line are among the most promising atomic transitions for applications in laser physics. They reach their maximum intensity in the 0.2–2 kG magnetic field range and are more intense than many conventional atomic transitions. An important feature of MI transitions is their large frequency shift with respect to the unperturbed hyperfine transitions which reaches ~12 GHz in magnetic fields of ~3 kG, while they are formed on the high-frequency wing of the spectrum and do not overlap with other transitions. Some important peculiarities have been demonstrated for the MI 5S_1/2 → 5P_3/2 transitions (λ = 780 nm). Particularly, it was shown that using a nanocell with thickness L = 100 nm it is possible to realize 1 μm-spatial resolution which is important when determining magnetic fields with strong spatial gradient (of >3G/μm). Earlier, our studies have been performed for 5S_1/2 → nP_3/2 transition with n = 5, while it is also theoretically shown to be promising for the transitions with n = 6, 7, 8 and 9, corresponding to the transition wavelengths of 420.2, 358.7, 334.9 and 322.8 nm, respectively.