A scenario of shielding and stabilization of magnetic and electromagnetic fields in the measuring volume occupied by a superconducting flux qubit is considered. The qubit is used as an artificial macroscopic atom with discrete energy levels in a counter of single photons of the microwave range. It is shown that a decrease in the amplitude of variations of the external magnetic field inside the 3-layer hybrid cylindrical shield, composed of superconducting and ferromagnetic cylinders with the diameter-to-length ratio of 1:5, provides high stability of the magnetic field. The absolute value of the magnetic field at the sample location is determined mainly by the magnetic flux captured by the superconductor shields during their superconducting transition. Although the magnetic field stability is more important than the field itself for the photon counter, the paper also discusses experimental methods for reducing the absolute field value in the hybrid shield.

The paper presents the results of mathematical treatment of the luminescent spectra of ZnSe nanocrystals. The samples were formed by the implantation of 150 keV Zn+ and 170 keV Se+ ions in silicon dioxide layer obtained by oxidation of a silicon substrate. We analyzed two sorts of the samples obtained with different implantation sequences: Zn+ were implanted first, and Se+ implanted next (sample A); reverse sequence with Se+ implanted at the beginning (sample B). The spectra obtained for different implantation sequences A and B differed from each other. It was found that besides the intensive evident bands with maxima at 2.3 eV (540 nm) and 2.85 eV (430 nm), which were associated with ZnSe intrinsic luminescent centers, there were two bands with maxima at 1.9 eV (650 nm) and 2.6 eV (480 nm), which were related to intrinsic SiO2 defects. Hereby the effect of the medium (silicon dioxide matrix) on luminescent spectra of SiO2 films with ZnSe nanocrystals formed by ion implantation was demonstrated. Mathematical treatment of the band shape with a maximum of 2.85 eV showed that the parameters such as full width at half maximum, skewness and kurtosis indicated the dependence of size distribution of ZnSe nanoparticles on the implantation sequence of ions. The results are in a good agreement with the data of Transmission Electron Microscopy.