Rain: Relaxations in the sky

We demonstrate how, from the point of view of energy flow through an open system, rain is analogous to many other relaxational processes in Nature such as earthquakes. By identifying rain events as the basic entities of the phenomenon, we show that the number density of rain events per year is inversely proportional to the released water column raised to the power 1.4. This is the rain-equivalent of the Gutenberg-Richter law for earthquakes. The event durations and the waiting times between events are also characterised by scaling regions, where no typical time scale exists. The Hurst exponent of the rain intensity signal $H = 0.76 > 0.5$. It is valid in the temporal range from minutes up to the full duration of the signal of half a year. All of our findings are consistent with the concept of self-organised criticality, which refers to the tendency of slowly driven non-equilibrium systems towards a state of scale free behaviour.Comment: 9 pages, 8 figures, submitted to PR

Entangling flux qubits with a bipolar dynamic inductance

We propose a scheme to implement variable coupling between two flux qubits using the screening current response of a dc Superconducting QUantum Interference Device (SQUID). The coupling strength is adjusted by the current bias applied to the SQUID and can be varied continuously from positive to negative values, allowing cancellation of the direct mutual inductance between the qubits. We show that this variable coupling scheme permits efficient realization of universal quantum logic. The same SQUID can be used to determine the flux states of the qubits.Comment: 4 pages, 4 figure

Flux Qubits and Readout Device with Two Independent Flux Lines

We report measurements on two superconducting flux qubits coupled to a readout Superconducting QUantum Interference Device (SQUID). Two on-chip flux bias lines allow independent flux control of any two of the three elements, as illustrated by a two-dimensional qubit flux map. The application of microwaves yields a frequency-flux dispersion curve for 1- and 2-photon driving of the single-qubit excited state, and coherent manipulation of the single-qubit state results in Rabi oscillations and Ramsey fringes. This architecture should be scalable to many qubits and SQUIDs on a single chip.Comment: 5 pages, 4 figures, higher quality figures available upon request. Submitted to PR

The Effect of Inquiry-Based, Hands-On Math Instruction Utilized in Combination with Web-Based, Computer-Assisted Math Instruction on 4th-Grade Students\u27 Outcomes

Results indicated that 4th-grade students ( n = 19) participating in the inquiry-based, hands-on math instruction used in combination with web-based, computer-assisted math instruction group and 4th-grade students ( n = 19) participating in the inquiry-based, hands-on math instruction alone group did not significantly improve their pretest-posttest Problem Solving/Data Analysis, Concepts/Estimation, Math Total, and Math Computation norm-referenced normal curve equivalent achievement test score results. However, 4th-grade students participating in the inquiry-based, hands-on math instruction alone group posttest-posttest scores were statistically significantly greater than students who participated in the combination instruction group across all four subtests. Moreover, all posttest norm-referenced, Normal Curve Equivalent subtest scores for both groups were measured within the average range. On the criterion-referenced math test score posttest-posttest comparison, 53% of the 4th-grade students participating in the inquiry-based, hands-on math instruction used in combination with web-based, computer-assisted math instruction group compared to 37% of the 4th-grade students participating in the inquiry-based, hands-on math instruction alone group improved their posttest score results. Finally, no statistically significant differences between the two instructional groups were found for student absences, tardies, discipline referrals, and perceptions of math ability scores. Implications for improving math instruction are discussed

Limitations of Segmented Wavefront Control Devices in Emulating Optical Turbulence

Using a device to act as a surrogate for atmospheric turbulence in a laboratory is necessary to build and test optical systems for imaging, lidar, laser weapons, and laser communications. Liquid-crystal spatial light modulators (LC SLMs) and segmented micro-electro-mechanical-system (MEMS) deformable mirrors (DMs) are commonly used devices for altering wavefronts in order to simulate a portion of atmospheric turbulence. The best location of these devices was theoretically analyzed to obtain the broadest possible range of atmospheric conditions. It was found that two phase screens should be placed at the beginning of the optical path to achieve maximum turbulence strength for an incident plane wave. It was also revealed that a layered model for atmospheric turbulence strength can be represented by the atmospheric coherence diameter that a single segmented wavefront control device can produce. The limitations of pixelation effects on a segmented wavefront control device were investigated theoretically. The results of this analysis were then confirmed in simulation. It was found that while LC SLMs with high bandwidth have almost no adverse effects from pixelation, segmented MEMS DMs have limitations as a result of the number of mirror segments on a DM. The performance capabilities of several available commercial devices are better understood as a result of this research

Superconducting qubit in waveguide cavity with coherence time approaching 0.1ms

We report a superconducting artificial atom with an observed quantum coherence time of T2*=95us and energy relaxation time T1=70us. The system consists of a single Josephson junction transmon qubit embedded in an otherwise empty copper waveguide cavity whose lowest eigenmode is dispersively coupled to the qubit transition. We attribute the factor of four increase in the coherence quality factor relative to previous reports to device modifications aimed at reducing qubit dephasing from residual cavity photons. This simple device holds great promise as a robust and easily produced artificial quantum system whose intrinsic coherence properties are sufficient to allow tests of quantum error correction