Temperature dependence of coherent oscillations in Josephson phase qubits

We experimentally investigate the temperature dependence of Rabi oscillations and Ramsey fringes in superconducting phase qubits driven by microwave pulses. In a wide range of temperatures, we find that both the decay time and the amplitude of these coherent oscillations remain nearly unaffected by thermal fluctuations. The oscillations are observed well above the crossover temperature from thermally activated escape to quantum tunneling for undriven qubits. In the two-level limit, coherent qubit response rapidly vanishes as soon as the energy of thermal fluctuations kT becomes larger than the energy level spacing of the qubit. Our observations shed new light on the origin of decoherence in superconducting qubits. The experimental data suggest that, without degrading already achieved coherence times, phase qubits can be operated at temperatures much higher than those reported till now.Comment: 4 pages, 4 figure

Фізична модель трьохкоординатного технологічного комплексу на базі СО2-Laser

В статье рассматривается физическая модель высокопроизводительного лазерного технологического комплекса (ЛТК) на основе CO2 –Laser SM-1200. У статті розглядаєтся фізична модель високопродуктивного лазерного технологічного комплекса (ЛТК) на основі CO2 –Laser SM-1200. In this article a physical model of a high-performance laser technological complex (LTC) on the basis of CO2-Laser SM-1200 is considered

A Gaussian approximation of the distributed computing process

The authors propose a refinement of the stochastic model describing the dynamics of the Desktop Grid (DG) project with many hosts and many workunits to be performed, originally proposed by Morozov et al. in 2017. The target performance measure is the mean duration of the runtime of the project. To this end, the authors derive an asymptotic expression for the amount of the accumulated work to be done by means of limit theorems for superposed on-off sources that lead to a Gaussian approximation. In more detail, depending on the distribution of active and idle periods, Brownian or fractional Brownian processes are obtained. The authors present the analytic results related to the hitting time of the considered processes (including the case in which the overall amount of work is only known in a probabilistic way), and highlight how the runtime tail distribution could be estimated by simulation. Taking advantage of the properties of Gaussian processes and the Conditional Monte-Carlo (CMC) approach, the authors present a theoretical framework for evaluating the runtime tail distribution

Evaluation of Cultural Impact on Regional Economic Development in Russia

Paper is devoted to Dependence of economic development of the Russian regions on their cultural level indicators. It determines and analyzes the influence degree of cultural components of the region development on its economic factors. The investigated statistical base consists of selected cultural and economic indices taken in the period of 2000-2015 years. The hypothesis of significant influence degree of the visits to museums and in particular, theatres number, on the amount of implemented innovational technologies was confirmed. A hypothesis about the close relationship between the volumes of expenditures of the Russian budget for culture and the level of research and development work, as well as directly the number of innovative industrial technologies introduced was confirmed. Hypotheses about the close interaction of cultural indices and such macroeconomic parameters as GDP growth, the volume of the capital investments have not been confirmed. A weak correlation between library holdings volume and the studied economic indicators was noted. The research can be used in design of the regional development programs, in forming budget priorities of budgets projects, or in taking other management decisions programming the basis for effective social and economic policy of the regions

Electron Temperature Relaxation in the Clusterized Ultracold Plasmas

Ultracold plasmas are a promising candidate for the creation of strongly-coupled Coulomb systems. Unfortunately, the values of the coupling parameter Gamma_e actually achieved after photoionization of the neutral atoms remain relatively small because of the large initial kinetic energy of the electrons. A conceivable way to get around this obstacle might be to utilize a spontaneous ionization of the ultracold Rydberg gas, where the initial kinetic energies could be much less. However, the spontaneous avalanche ionization will result in a very inhomogeneous distribution (clusterization) of the ions, which can change the efficiency of the electron relaxation in the vicinity of such clusters substantially. In the present work, this hypothesis is tested by an extensive set of numerical simulations. As a result, it is found that despite less initial kinetic energy, the subsequent relaxation of the electron velocities in the clusterized plasmas proceeds much more violently than in the case of the statistically-uniform ionic distribution. The electron temperature, firstly, experiences a sharp initial jump (presumably, caused by the "virialization" of energies of the charged particles) and, secondly, exhibits a gradual subsequent increase (presumably, associated with a multi-particle recombination of the electrons at the ionic clusters). As a possible tool to reduce the anomalous temperature increase, we considered also a two-step plasma formation, involving the blockaded Rydberg states. This leads to a suppression of the clusterization due to a quasi-regular distribution of ions. In such a case, according to the numerical simulations, the subsequent evolution of the electron temperature proceeds more gently, approximately with the same rate as in the statistically-uniform ionic distribution.Comment: LaTeX2e, revtex4-1 documentclass, 8 pages, 8 EPS figure

Enhanced Macroscopic Quantum Tunneling in Bi2_2Sr2_2CaCu2_2O8+δ_{8+\delta} Intrinsic Josephson Junction Stacks

We have investigated macroscopic quantum tunneling in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ intrinsic Josephson junctions at millikelvin temperatures using microwave irradiation. Measurements show that the escape rate for uniformly switching stacks of N junctions is about $N^2$ times higher than that of a single junction having the same plasma frequency. We argue that this gigantic enhancement of macroscopic quantum tunneling rate in stacks is boosted by current fluctuations which occur in the series array of junctions loaded by the impedance of the environment.Comment: 4 pages and 5 figure

Multi-photon spectroscopy of a hybrid quantum system

We report on experimental multi-photon spectroscopy of a hybrid quantum system consisting of a superconducting phase qubit coherently coupled to an intrinsic two-level defect. We directly probe hybridized states of the combined qubit-defect system in the strongly interacting regime, where both the qubit-defect coupling and the driving cannot be considered as weak perturbations. This regime is described by a theoretical model which incorporates anharmonic corrections, multi-photon processes and decoherence. We present a detailed comparison between experiment and theory and find excellent agreement over a wide range of parameters.Comment: 6 pages, 6 figure

Measuring the temperature dependence of individual two-level systems by direct coherent control

We demonstrate a new method to directly manipulate the state of individual two-level systems (TLS) in phase qubits. It allows one to characterize the coherence properties of TLS using standard microwave pulse sequences, while the qubit is used only for state readout. We apply this method to measure the temperature dependence of TLS coherence for the first time. The energy relaxation time $T_1$ is found to decrease quadratically with temperature for the two TLS studied in this work, while their dephasing time measured in Ramsey and spin-echo experiments is found to be $T_1$ limited at all temperatures.Comment: 4 pages, 5 figure