High Bias Transport and Magnetometer Design in Open Quantum Dots

We report transport measurements as a function of bias in open semiconductor quantum dots. These measurements are well described by an effective electron temperature derived from Joule heating at the point contacts and cooling by Wiedemann-Franz out-diffusion of thermal electrons. Using this model, we propose and analyze a quantum dot based sensor which measures absolute magnetic field at micron scales with a noise floor of $\sim 50 \mu\phi_{0} / \sqrt{Hz}$ at 300 mK.Comment: 10 pages including 3 figure

Probe-configuration dependent dephasing in a mesoscopic interferometer

Dephasing in a ballistic four-terminal Aharonov-Bohm geometry due to charge and voltage fluctuations is investigated. Treating two terminals as voltage probes, we find a strong dependence of the dephasing rate on the probe configuration in agreement with a recent experiment by Kobayashi et al. (J. Phys. Soc. Jpn. 71, 2094 (2002)). Voltage fluctuations in the measurement circuit are shown to be the source of the configuration dependence.Comment: 4 pages, 3 figure

Calculation of dephasing times in closed quantum dots

Dephasing of one-particle states in closed quantum dots is analyzed within the framework of random matrix theory and Master equation. Combination of this analysis with recent experiments on the magnetoconductance allows for the first time to evaluate the dephasing times of closed quantum dots. These dephasing times turn out to depend on the mean level spacing and to be significantly enhanced as compared with the case of open dots. Moreover, the experimental data available are consistent with the prediction that the dephasing of one-particle states in finite closed systems disappears at low enough energies and temperatures.Comment: 4 pages, 3 figure

Conductance fluctuations and weak localization in chaotic quantum dots

We study the conductance statistical features of ballistic electrons flowing through a chaotic quantum dot. We show how the temperature affects the universal conductance fluctuations by analyzing the influence of dephasing and thermal smearing. This leads us to two main findings. First, we show that the energy correlations in the transmission, which were overlooked so far, are important for calculating the variance and higher moments of the conductance. Second, we show that there is an ambiguity in the method of determination of the dephasing rate from the size of the of the weak localization. We find that the dephasing times obtained at low temperatures from quantum dots are underestimated.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let

3rd KidRec workshop: What does good look like?

Today's children spend considerable time online, searching and receiving information from various websites and apps. While searching for information, e.g. for school or hobbies, children use search systems to locate resources and receive site recommendations that might be useful for them. The call for good, reliable, child-friendly systems has been made many times and the thesis that the algorithms of "adult" information systems are not necessarily suitable or fair for children is widely accepted. However, there is still no clear and balanced view on what makes one search/recommendation system for children good or better than other systems, nor on what content should be considered "good enough to be retrieved" or recommended. The goal of this workshop is to bring together researchers and practitioners in education, child-development, computer science, and more who can address this questions while considering issues related to education, algorithms, ethics, privacy, evaluation

De beslispraktijk van het Schadefonds Geweldsmisdrijven: een kwalitatieve studie naar de beoordeling van verzoeken tot tegemoetkoming

The Violent Offences Compensation Fund’s decision-making practice: A qualitative study into the evaluation of requests for compensation Victims who suffer severe damages due to the act of a violent crime can request state compensation from the Dutch Violent Offences Compensation Fund (VOCF). VOCF workers who decide on these requests use their discretionary powers to translate the VOCF’s rules and policy into concrete actions. This study investigated (1) to what extent these VOCF workers match Lipsky’s definition of street-level bureaucrats and (2) what routines and heuristics they use to deal with time and information constraints. On the basis of document analysis and interviews, we found that the decision makers of the VOCF can to a certain extent be seen as street-level bureaucrats. To make decisions timely, some of them use routines such as the ‘downstream orientation’. This means that they award requests for compensation if they think that the applicant would be able to successfully contest a rejecting decision. To deal with a lack of information, they sometimes include a review clause in the text of a rejection decision. The use of heuristics was not found among the lawyers who decide in first instance, but in case of appeal hearings heuristics such as the affect and representativeness heuristic seem to play a role in the decision-making process. Future research should investigate whether these routines and heuristics lead to disparities in outcomes. Criminal Justice: Legitimacy, accountability, and effectivit

Photocurrent, Rectification, and Magnetic Field Symmetry of Induced Current Through Quantum Dots

We report mesoscopic dc current generation in an open chaotic quantum dot with ac excitation applied to one of the shape-defining gates. For excitation frequencies large compared to the inverse dwell time of electrons in the dot (i.e., GHz), we find mesoscopic fluctuations of induced current that are fully asymmetric in the applied perpendicular magnetic field, as predicted by recent theory. Conductance, measured simultaneously, is found to be symmetric in field. In the adiabatic (i.e., MHz) regime, in contrast, the induced current is always symmetric in field, suggesting its origin is mesoscopic rectification.Comment: related papers at http://marcuslab.harvard.ed

«Белая дача» А.П. Чехова – как часть культурного ландшафта Крыма

Данная работа написана в рамках научного проекта кафедры культурологии «Культурные ландшафты Крыма» и посвящена рассмотрению «Белой дачи» А.П. Чехова (ныне Дом-музей А.П. Чехова в Ялте) как культурному ландшафту – результату сотворчества человека и природы