The resonant microwave pulses have been shown to be able to create magnetization of high-spin (S ≥ 1) metal ions even in the absence of an external magnetic field. This transformation of the ion spin states is similar to the “alignment–orientation” transition in atomic spectroscopy. These manipulations make it possible to translate the results of elementary quantum computing operations performed in zero magnetic fields into physically observable quantities.
New heptanuclear mixed-valence iron complexes with pentadentate ligands are synthesized, and their magnetic properties are analyzed. Magnetometry and EPR show that thiocyanate anions promote spin-crossover properties. Introducing long alkoxy chains into a molecule gives it thermotropic liquid crystalline properties and enhances its cooperative magnetic properties.
A systematic study is performed of the superconductor/normal metal, superconductor/antiferromagnet, and superconductor/ferromagnet proximity effects in structures with superconducting lead layers of variable thickness. It is shown that temperature Ts of the superconducting transition in these systems behaves differently when the superconducting layer is thinned. In superconductor/antiferromagnet structures, Ts changes negligibly within the investigated range of lead layer thickness. Ratio RRR (R300 K/R10 K) of electrical resistance falls notably as the lead layer thins, which could indicate a growing contribution from surface defects. The width of superconducting transitions grows as the lead layer thins, testifying to size effects.
Properties of an Fe1/Cu/Fe2/Cu/Pb superconducting spin valve formed on a [Pb(Mg1/3Nb2/3)O3]0.7‒[PbTiO3]0.3 (PMN‒PT) piezoelectric substrate are studied in external magnetic and electric fields. The temperature of the superconducting transition shifts by more than 200 mK upon changing the mutual orientation of the ferromagnetic layer magnetizations from antiparallel to perpendicular in magnetic field H0 = 1 kOe. Anomalous behavior of the dependence of the temperature of the superconducting transition on the angle between the magnetizations of the ferromagnetic layers is observed in the maximum temperatures of the superconducting transition at an orthogonal orientation of the magnetizations of the ferromagnetic layers. The possibility of obtaining a full superconducting spin valve effect is demonstrated. It is established that the shift of the temperature of the superconducting transition grows along with an electric field applied to the PMN‒PT piezoelectric substrate. A maximum shift of 10 mK is detected in an electric field of 1 kV/cm.
We analyze the performance of quantum repeaters where the protocols of entanglement generation and swapping are based on multimode optical Schrödinger cat states produced using electro-optic modulation of single-mode optical cats. We employ both the mean-only approximation and exact results to calculate the distance dependencies of the mean waiting time and the repeater rate depending on the number of elementary links. The results are compared with the rates of quantum repeater schemes based on photon pairs generated via spontaneous parametric down-conversion.
A spectral and luminescence study was made of the efficiency of phototransformation of sulfaguanidine in water under irradiation with an OUVb-04 ultraviolet lamp (180–275 nm) and KrCl (222 nm), XeBr (282 nm), and XeCl (308 nm) excilamps. An analysis of the conversion of sulfaguanidine in water showed that the efficiency of sulfaguanidine phototransformation in water under irradiation with the XeBr excilamp is comparable to the loss under irradiation with OUVb-04, but higher than those under irradiation with the KrCl and XeCl excilamps. The maximum loss of sulfaguanidine is 99% without the introduction of additional oxidizing agents. After irradiation, several photoproducts of various nature were detected.
The generation of terahertz radiation by atomic systems interacting with femtosecond two-color laser fields (left( {{{omega }_{1}} + {{omega }_{2}}} right)) formed by the fundamental harmonic of a laser source (left( {{{omega }_{1}}} right)) and radiation with frequencies varying over a wide range (left( {{{omega }_{2}}} right)) is studied. It is shown that the efficiency of the generation of terahertz radiation grows when ratio (({{omega }_{2}}{text{/}}{{omega }_{1}})) of frequencies between components of the two-color field is close but not equal to 2, and difference (left| {{{omega }_{2}} - 2{{omega }_{1}}} right|) corresponds to the terahertz range. A numerical experiment is performed using laser sources with wavelengths from the near- to far-infrared range.
Trapped bosonic atoms can be cooled down to temperatures where the atomic cloud experiences Bose–Einstein condensation. Almost all atoms in a dilute gaseous system can be Bose-condensed, which implies that this system is in a coherent state. The coherent atomic system enjoys many properties typical of coherent optical systems. It is possible to generate different condensate coherent modes similarly to the generation of optical modes. Several effects can be observed, such as interference patterns, interference current, Rabi oscillations, harmonic generation, parametric conversion, Ramsey fringes, mode locking, dynamic transition between Rabi and Josephson regimes, and atomic squeezing.
The possibility of practical implementation was studied for a quantum communication link for encryption key distribution between the Micius satellite and a mobile ground optical station. Using theoretical estimation, numerical values of the main parameters of such a communication link were obtained: total loss, key generation rate and secret key length, as well as quantum bit error rate.
The authors study characteristics of lasing on molecular nitrogen ions in laser plasma created by a femtosecond radiation pulse. The maximum intensities at wavelengths of 391.4 and 427.8 nm are observed at nitrogen pressures of 30 and 500 mbar, respectively. The divergence of radiation is tens mrad and close to geometric. The pulse length at a wavelength of 391.4 nm varies from 1.83 to 3.5 ps upon changing the focal length of the lens from 15 to 40 cm.
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