Leggett-Garg inequality with a kicked quantum pump

A kicked quantum nondemolition measurement is introduced, where a qubit is weakly measured by pumping current. Measurement statistics are derived for weak measurements combined with single-qubit unitary operations. These results are applied to violate a generalization of the Leggett-Garg inequality. The violation is related to the failure of the noninvasive detector assumption, and may be interpreted as either intrinsic detector backaction, or the qubit entangling the microscopic detector excitations. The results are discussed in terms of a quantum point contact kicked by a pulse generator, measuring a double quantum dot.     

Measure-compact operators, almost compact operators, and linear functional equations in L p

Under study are the measure-compact operators and almost compact operators in L _p . We construct an example of a measure-compact operator that is not almost compact. Introducing two classes of closed linear operators in L _p , we prove that the resolvents of these operators are almost compact or measure-compact. We present methods for the reduction of linear functional equations of the second kind in L _p with almost compact or measure-compact operators to equivalent linear integral equations in L _p with quasidegenerate Carleman kernels.     

Amplitude dependences of dielectric permittivity and dielectric losses in a mixed K0.88(NH4)0.12H2PO4 crystal

Amplitude dependences of dielectric permittivity ? and dielectric losses tanδ in K_0.88(NH₄)_0.12H₂PO₄ mixed crystal near the ferroelectric phase transition temperature T _C are investigated. At measurement fields E _～ exceeding some critical value, dependence tanδ(E _～) can be described within a model that includes the depinning of domain walls from point lattice defects. The activation field is found to grow appreciably when approaching T _C from below, due to the presence of nonpolar regions.     

Studying the dielectric, electromechanical, and elastic properties of K1 − x (NH4) x H2PO4 mixed crystals

Temperature dependences of the longitudinal permittivity, piezoelectric coefficient d ₃₆, and elastic constant c ₆₆ ^E of K_{1 ? x} (NH₄) _x H₂PO₄ mixed crystals are studied experimentally. A microscopic model is proposed for crystals of the K_{1 ? x} (NH₄) _x H₂PO₄ type that includes the piezoelectric contribution to the effective pseudospin cluster Hamiltonian. Dielectric elastic and electromechanical properties of these crystals with ammonium concentrations x below 0.40 are calculated in a wide temperature range using the cluster approach. The calculation results are in qualitative agreement with experimental data.     

Experiments on the search for the effect of resonant screening on the probability of Mössbauer absorption of <Superscript>119<Emphasis Type="Italic">m</Emphasis></Superscript>Sn gamma rays

Experiments on the search for the effect of resonant screening on the Mössbauer absorption of ^119m Sn γ rays of energy 23.8 keV emitted by a standard Mössbauer Ca^119m SnO₃ γ source in the resonant SnO₂ absorber of natural isotopic composition are described. Intensities of tin γ rays and X-rays that passed through the absorber were measured with and without a resonant cylindrical screen (which was a black absorber for the 23.8-keV Mössbauer γ line) around the absorber and their ratios were calculated for each radiation separately. No difference beyond the experimental error was found between these ratios measured with the γ source both at rest and when oscillating with a frequency and amplitude enough to completely break the conditions for Mössbauer resonant absorption of 23.8-keV γ rays. The upper limit for the relative decrease, due to the influence of the resonant screen, in the intensities of these γ rays after their passing through the resonant absorber was 0.00030.     

Size effect of phase transformation temperature in a contact between thin metal films

It is established experimentally that the contact fusion temperature for lead-bismuth and lead-tin films decreases with the thickness of contacting films.     

Transitions to the relaxor and dipole-glass states in mixed crystals of the potassium dihydrogen phosphate family

Regularities of the formation of the relaxor and dipole-glass states in the systems of mixed ferroelectric-antiferroelectric crystals of the potassium dihydrogen phosphate family are discussed. The problems related to the crystal structure, lattice dynamics, and relaxation processes in dipole glasses and relaxors implemented in systems of this type are considered.     

Absence of the resonant environment effect on the half-life of the <Superscript>119<Emphasis Type="Italic">m</Emphasis></Superscript>Sn isomer in the standard Mössbauer <Emphasis Type="Italic">γ</Emphasis>-ray source

Nine sets of measurements aimed at searching for the influence of resonant environment on the half-life of the ^109m Sn isomer have been performed during 14.7 months. The intensities of γ and X rays, emitted by two 261Mössbauer sources of identical design and size, were compared in these experiments. One of the sources was kept in the resonant environment of tin dioxide between measurements. No difference was found in the half-lives of ^119m Sn that would be beyond the experimental errors (0.35%).     

Observation of the gamma resonance of a long-lived <Superscript>109<Emphasis Type="Italic">m</Emphasis></Superscript>Ag isomer using a gravitational gamma-ray spectrometer

Experiments confirming the previous data on the small real width of the γ resonance of ^109m Ag have been performed with a gravitational gamma-ray spectrometer. The achieved resolution is eight orders of magnitude higher than that of Mössbauer spectrometers using gamma rays from a ⁵⁷Fe nuclide. The theoretically predicted broadening of the Mössbauer gamma line of ^109m Ag by five orders of magnitude (due to the dipole-dipole interaction between the magnetic moments of neighboring nuclei) has not been observed.     

A study of the nuclear-medium influence on neutral-strange-particle production in deep-inelastic neutrino scattering

The influence of nuclear effects on the production of neutral strange particles (V ⁰) is investigated using the data obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam (with E _v =3−30 GeV) at the Serpukhov accelerator. The mean multiplicity of V ⁰ particles in nuclear interactions, , is found to exceed significantly that in “quasideuteron” interactions, . The ratio of is larger than that for π⁻ mesons, . It is shown that the multiplicity gain of V ⁰ particles can be explained by intranuclear interactions of produced pions. The text was submitted by the authors in English.