A quantum volume hologram

We propose a new scheme for parallel spatially multimode quantum memory for light. The scheme is based on counter-propagating quantum signal wave and strong classical reference wave, like in a classical volume hologram, and therefore can be called a quantum volume hologram. The medium for the hologram consists of a spatially extended ensemble of atoms placed in a magnetic field. The write-in and read-out of this quantum hologram is as simple as that of its classical counterpart and consists of a single pass illumination. In addition we show that the present scheme for a quantum hologram is less sensitive to diffraction and therefore is capable of achieving higher density of storage of spatial modes as compared to previous proposals. A quantum hologram capable of storing entangled images can become an important ingredient in quantum information processing and quantum imaging.Comment: 8 pages, 2 figure

Estimation of the Operating Parameters of Miniature Radioisotope Thermoelectric Power Unit Based on the Th-228 Isotope

The article considers the construction of a miniature radioisotope power unit based on thermoelectric conversion of thermal energy released during nuclear decay. It is proposed to use thin fluoropolymer films (membranes) as a dielectric heat-insulating material. The results of numerical simulation of a prototype of a miniature radioisotope thermoelectric battery unit based on the thorium-228 isotope in the ANSYS program are presented. The geometry of the system has been optimized. It was established that the temperature of the source can reach about 1033 K, and the efficiency of the considered battery unit can reach 16.8%, which corresponds to modern power supplies of this type

Experimental studies of thorium ions implantation from pulse laser plasma into thin silicon oxide layers

We report the results of experimental studies related to implantation of thorium ions into thin silicon dioxide by pulsed plasma fluxes expansion. Thorium ions were generated by laser ablation from a metal target, and the ionic component of the laser plasma was accelerated in an electric field created by the potential difference (5, 10 and 15 kV) between the ablated target and SiO2/Si(001) sample. Laser ablation system installed inside the vacuum chamber of the electron spectrometer was equipped with YAG:Nd3+ laser having the pulse energy of 100 mJ and time duration of 15 ns in the Q-switched regime. Depth profile of thorium atoms implanted into the 10 nm thick subsurface areas together with their chemical state as well as the band gap of the modified silicon oxide at different conditions of implantation processes were studied by means of X-ray photoelectron spectroscopy (XPS) and Reflected Electron Energy Loss Spectroscopy (REELS) methods. Analysis of chemical composition showed that the modified silicon oxide film contains complex thorium silicates. Depending on local concentration of thorium atoms, the experimentally established band gaps were located in the range of 6.0 - 9.0 eV. Theoretical studies of optical properties of the SiO2 and ThO2 crystalline systems have been performed by ab initio calculations within hybrid functional. Optical properties of the SiO2/ThO2 composite were interpreted on the basis of Bruggeman effective medium approximation. A quantitative assessment of the yield of isomeric nuclei in "hot" laser plasma at the early stages of expansion has been performed. The estimates made with experimental results demonstrated that the laser implantation of thorium ions into the SiO2 matrix can be useful for further research of low-lying isomeric transitions in 229Th isotope with energy of 7.8(0.5) eV

Modelling of viscoelastic plume-lithosphere interaction using the adaptive multilevel wavelet collocation method

Modelling of mantle flows with sharp viscosity contrasts in a viscoelastic medium is a challenging computational problem in geodynamics because of its multiple-scale nature in space and time. We have employed a recently developed adaptive multilevel wavelet collocation algorithm to study the dynamics of a small rising diapir interacting with a stiff lithosphere in a Maxwell viscoelastic mantle. In this kinematic model we have prescribed the upward velocity of the diapir and then we need to integrate in time onlythe momentum equation governing the temporal evolution of the pressure, stress andvelocity components, which together constitute a sixth-order system in time. The total number of collocation points did not exceed 104, compared to more than 106 gridpoints using conventional evenly spaced grid methods. The viscosity of the diapir is10−4 times lower than that of the surrounding mantle, while the viscosity of the thinlithosphere, about 5-10 per cent of the entire layer depth, is 104-108 times stiffer than the ambient mantle. Our results demonstrate the efficacy of wavelets to capture thesharp gradients of the stress and pressure fields developed in the diapiric impingement process. The interaction of the viscoelastic lithosphere with therisingviscoelastic diapir results in the localization of stress within the lithosphere. The magnitude of the stress fields can reach around 100-300 MPa. Our simple kinematic model shows clearly that viscoelasticity canpotentially play an important role in the dynamics of thelithosphere, especially concerning the potential severage of the lithosphere by mantle upwelling

Linear magnetoresistance in compensated graphene bilayer

We report a nonsaturating linear magnetoresistance in charge-compensated bilayer graphene in a temperature range from 1.5 to 150 K. The observed linear magnetoresistance disappears away from charge neutrality ruling out the traditional explanation of the effect in terms of the classical random resistor network model. We show that experimental results qualitatively agree with a phenomenological two-fluid model taking into account electron-hole recombination and finite-size sample geometry

Formation and Study of Properties of Ta and Mo Nanocluster Films

In this article, the results of studies of thin-film samples of nanoclusters of tantalum and molybdenum metals on the surface of silicon dioxide SiO2 /Si (001) at room temperature are presented. The chemical composition and electronic structure of the obtained nanocluster films of Ta and Mo were controlled in situ by X-ray photoelectron spectroscopy (XPS). Susceptibility to oxidation during the exposure to the atmosphere of then nanocluster films, as well as their thermal stability when heated in a vacuum to 600∘C were studied ex situ by the XPS method. The size and shape of the nanoclusters composing the film were estimated ex situ by analyzing images obtained with a scanning electron microscope. The band structure before and after oxidation was studied by measuring the bandgap of the formed Ta and Mo films by the method of electron energy loss characteristic spectroscopy (REELS). Conclusions about thermoelectric properties of the formed nanocluster films of Ta and Mo were made