Precision measurements of heat capacity C_p were performed in a magnetic field of up to 90 kOe in the vicinity of the Neel temperature T_N in hexaborides NdB6, GdB6, and TbB6 with Jahn–Teller (JT) structural instability, critical behavior C_p(T) was studied. It has been established that the phase transformation in these RB6 belongs to the class of “weak” first-order phase transitions, close to second-order phase transitions, with a small jump value ΔC_p in GdB6, and the behavior C_p(T) in a wide vicinity T_N is well described by critical indices γ_i (i = AF and P), which are typical for λ -anomalies. For NdB6 and GdB6 γ_AF and γ_P take values - (1- 1.4) , found in various models for “pure” second-order phase transitions. In strong fields up to 90 kOe, critical values significantly deviate from the model values. For TbB6 γ_AF , γ_P∼ - 2 received, indicating a more pronounced “magnitude of 1st order transition” effect.
A method is proposed for using large-aperture pinhole cameras to record high-spatial-resolution images of low-intensity, small-sized plasma X-ray sources. To implement this method specifically for large-diameter pinhole cameras, a mathematical procedure for image reconstruction was developed and applied, based on an iteration method for solving an ill-posed problem—the Fredholm integral equation of the first kind with a special instrumental function. Based on model and experimental images, it is shown that the use of such a procedure makes it possible to obtain reconstructed images of the source with a spatial resolution significantly better than the intrinsic geometric resolution of large-aperture pinhole cameras. Thus, a real opportunity has emerged for using easy-to-manufacture large-aperture pinholes with high light intensity in experimental diagnostics, which were previously not usually used for studying X-ray plasma sources.
The fluctuations in the response of a terahertz superconducting hot electron bolometer, associated with the discreteness of photon absorption events, during the detection of weak radiation fluxes, were theoretically studied. It is shown that the nonlinear dependence of the resistance of a superconducting NbN film near the critical temperature leads to an asymmetric distribution of the local temperature of the electron subsystem; an analytical expression for this distribution is obtained. Using numerical simulation, it is shown that the proximity of the bolometer operating point to the instability region located in the section of the negative slope of the current-voltage characteristic of the superconducting film, at weak radiation fluxes, can lead to a significant asymmetry in the distribution of the bolometer response and even to its non-monotonic dependence on the radiation intensity.
Mid-circuit measurement of individual qubits is a necessary element in the implementation of quantum error correction protocols and allows for the reduction of resource requirements for the execution of a number of quantum algorithms. In this paper, we present a protocol for mid-circuit measurement of qubits implemented at an optical transition ^2S_1/2(F = 0,m_F = 0)→^2D_3/2(F = 2,m_F = 0) in ions 171Yb+. The proposed protocol enables selective measurement of a subset of qubits (target qubits) without destroying the state of the rest (spectator qubits). The method involves the use of an auxiliary state ^2D_3/2(F = 1) , as well as a spin echo technique to maintain the coherence of the spectator qubits during the operation. The average reliability of the target qubit measurement operation of 98.2(1)
Based on the analysis of the results obtained by the numerical Monte Carlo method for a system of hard spheres, it was established that the quantum contribution to its energy E , calculated for one particle increases with increasing temperature T how √(T) : E = 3/2T + δ(ε_0T)^1/2 , ε_0 = h^2/2π Mσ^2 ; where M and σ —mass and diameter of spheres, δ is a parameter depending on the density of the system of hard spheres. This contribution is proportional to the first power of Planck’s constant h . The interpolation formula for heat capacity is substantiated C_V : C_V(λ ) = 3/2 + δ/2λ (1 - λ^2) , where λ is the ratio of the wavelength of the particles to their diameter: λ = (ε_0/T)^1/2 . At λ = 1 C_V for the system of hard spheres has a fan-shaped point dividing the regions of high T > ε_0 and low T < ε_0 temperature. The result was a comparison of the model system with a physical liquid 4He, for whom such a fan-shaped point is visible in the experiment. Near this point, the model system and liquid 4He They have the same linear pressure dependence P from temperature T, characteristic of an ideal gas, as well as the same dependence of entropy on dimensionless density.
