Characterization of a Differential Radio-Frequency Single-Electron Transistor

We have fabricated and characterized a new type of electrometer that couples two parallel single-electron transistors (SETs) to a radio-frequency tank circuit for use as a differential RF-SET. We demonstrate operation of this device in summing, differential, and single-SET operation modes, and use it to measure a Coulomb staircase from a differential single Cooper-pair box. In differential mode, the device is sensitive to uncorrelated input signals while screening out correlated ones.Comment: 3 pages, 3 figures, submitted to Applied Physics Letter

An optimization approach to adaptive multi-dimensional capital management

Firms should keep capital to offer sufficient protection against the risks they are facing. In the insurance context methods have been developed to determine the minimum capital level required, but less so in the context of firms with multiple business lines including allocation. The individual capital reserve of each line can be represented by means of classical models, such as the conventional Cram\'{e}r-Lundberg model, but the challenge lies in soundly modelling the correlations between the business lines. We propose a simple yet versatile approach that allows for dependence by introducing a common environmental factor. We present a novel Bayesian approach to calibrate the latent environmental state distribution based on observations concerning the claim processes. The calibration approach is adjusted for an environmental factor that changes over time. The convergence of the calibration procedure towards the true environmental state is deduced. We then point out how to determine the optimal initial capital of the different business lines under specific constraints on the ruin probability of subsets of business lines. Upon combining the above findings, we have developed an easy-to-implement approach to capital risk management in a multi-dimensional insurance risk model

Scaling Analysis of Magnetic Filed Tuned Phase Transitions in One-Dimensional Josephson Junction Arrays

We have studied experimentally the magnetic field-induced superconductor-insulator quantum phase transition in one-dimensional arrays of small Josephson junctions. The zero bias resistance was found to display a drastic change upon application of a small magnetic field; this result was analyzed in context of the superfluid-insulator transition in one dimension. A scaling analysis suggests a power law dependence of the correlation length instead of an exponential one. The dynamical exponents $z$ were determined to be close to 1, and the correlation length critical exponents were also found to be about 0.3 and 0.6 in the two groups of measured samples.Comment: 4 pages, 4 figure

Capacitively coupled Josephson-junction chains: straight and slanted coupling

Two chains of ultrasmall Josephson junctions, coupled capacitively with each other in the two different ways, straight and slanted coupling, are considered. As the coupling capacitance increases, regardless of the coupling scheme, the transport of particle-hole pairs in the system is found to drive the quantum-phase transition at zero temperature, which is a insulator-to-superfluid transition of the particle-hole pairs and belongs to the Berezinskii-Kosterlitz-Thouless universal class. The different underlying transport mechanisms for the two coupling schemes are reflected in the difference between the transition points.Comment: REVTeX + 7 EPS figures, detailed version of cond-mat/980219

It’s not just the Therapist: Therapist and Country-Wide Experience Predict Therapist Adherence and Adolescent Outcome

Contains fulltext : 173905.pdf (publisher's version ) (Open Access)Objective: Therapist adherence is a quality indicator in routine clinical care when evaluating the success of the implementation of an intervention. The current study investigated whether therapist adherence mediates the association between therapist, team, and country-wide experience (i.e. number of years since implementation in the country) on the one hand, and treatment outcome on the other hand. We replicated and extended a study by Löfholm et al. (2014). Method: Data over a 10-year period were obtained from 4290 adolescents (12-17 years) with antisocial or delinquent problem behavior, who were treated with Multisystemic Therapy (MST) by 222 therapists, working in 27 different teams in the Netherlands. Multilevel structural equation modeling was used to assess the associations between experience, therapist adherence, and post-treatment outcomes. Results: Treatment outcomes were directly predicted by therapist experience, countrywide experience, and therapist adherence, but not by team experience. Moreover, therapist adherence mediated the association between therapist and country-wide experience, and treatment outcomes. The association between therapist experience and therapist adherence was not affected by the number of years of team experience or country-wide experience. Conclusion: The effect of country-wide experience on outcome may reflect increasing experience of training and supporting the therapists. It suggests that nation-wide quality control may relate to better therapist adherence and treatment outcome for adolescents treated with systemic therapy.17 p

Escape from a zero current state in a one dimensional array of Josephson junctions

A long one dimensional array of small Josephson junctions exhibits Coulomb blockade of Cooper pair tunneling. This zero current state exists up to a switching voltage, Vsw, where there is a sudden onset of current. In this paper we present histograms showing how Vsw changes with temperature for a long array and calculations of the corresponding escape rates. Our analysis of the problem is based on the existence of a voltage dependent energy barrier and we do not make any assumptions about its shape. The data divides up into two temperature regimes, the higher of which can be explained with Kramers thermal escape model. At low temperatures the escape becomes independent of temperature.Comment: 4 pages 5 figure

Quantum Glass Transition in a Periodic Long-Range Josephson Array

We show that the ground state of the periodic long range Josephson array frustrated by magnetic field is a glass for a sufficiently large Josephson energies despite the absence of a quenched disorder. Like superconductors, this glass state has non-zero phase stiffness and Meissner response; for smaller Josephson energies the glass "melts" and the ground state loses the phase stiffness and becomes insulating. We find the critical scaling behavior near this quantum phase transition: the excitation gap vanishes as (J-J_c)^2, the frequency-dependent magnetic susceptibility behaves as \chi(\omega) ~ \sqrt{\omega}\ln{\omega}.Comment: 9 pages, Latex, 3 figures in separated eps-file

Parity Effect and Charge Binding Transition in Submicron Josephson Junction Arrays

We reconsider the issue of Berezinskii-Kosterlitz-Thouless (BKT) transition into an insulating state in the Coulomb-dominated Josephson junction arrays. We show that previously predicted picture of the Cooper-pair BKT transtion at T = T_2 is valid only under the condition that T_2 is considerably below the parity-effect temperature (which is usually almost 10 times below the value of superconductive transition temperature), and even in this case it is not a rigorous phase transition but only a crossover, whereas the real phase transition takes place at T_1 = T_2/4. Our theory is in agreement with available experimental data on Coulomb-dominated Josephson arrays and also sheds some light on the origin of unusual reentrant temperature dependence of resistivity in the array with nearly-criticial ratio of Coulomb to Josephson energies.Comment: 4 pages, Revtex, to be published in JETP Letters, April 9

Quantum superconductor-metal transition in a proximity array

A theory of the zero-temperature superconductor-metal transition is developed for an array of superconductive islands (of size d) coupled via a disordered two-dimensional conductor with the dimensionless conductance g>>1. At T=0 macroscopically superconductive state of the array with the lattice spacing b>>d is destroyed at g < g_c \approx 0.1 ln^2(b/d). At high temperatures the normal-state resistance between neighboring islands at b=b_c is much smaller than h/4e^2.Comment: RevTeX, 7 pages, 2 eps figure