Detection of Quantum Noise from an Electrically-Driven Two-Level System

Quantum mechanics can strongly influence the noise properties of mesoscopic devices. To probe this effect we have measured the current fluctuations at high-frequency (5-90 GHz) using a superconductor-insulator-superconductor tunnel junction as an on-chip spectrum analyser. By coupling this frequency-resolved noise detector to a quantum device we can measure the high-frequency, non-symmetrized noise as demonstrated for a Josephson junction. The same scheme is used to detect the current fluctuations arising from coherent charge oscillations in a two-level system, a superconducting charge qubit. A narrow band peak is observed in the spectral noise density at the frequency of the coherent charge oscillations.Comment: 16 pages, 4 figure

Constraining Holocene hydrological changes in the Carpathian–Balkan region using speleothem δ18O and pollen-based temperature reconstructions

Here we present a speleothem isotope record (POM2) from Ascunsă Cave (Romania) that provides new data on past climate changes in the Carpathian–Balkan region from 8.2 ka until the present. This paper describes an approach to constrain the effect of temperature changes on calcite δ18O values in stalagmite POM2 over the course of the middle Holocene (6–4 ka), and across the 8.2 and 3.2 ka rapid climate change events. Independent pollen temperature reconstructions are used to this purpose. The approach combines the temperature-dependent isotope fractionation of rain water during condensation and fractionation resulting from calcite precipitation at the given cave temperature. The only prior assumptions are that pollen-derived average annual temperature reflects average cave temperature, and that pollen-derived coldest and warmest month temperatures reflect the range of condensation temperatures of rain above the cave site. This approach constrains a range of values between which speleothem δ18O changes should be found if controlled only by surface temperature variations at the cave site. Deviations of the change in δ18Ocspel values from the calculated temperature-constrained range of change are interpreted towards large-scale variability of climate–hydrology. Following this approach, we show that an additional ∼0.6‰ enrichment of δ18Oc in the POM2 stalagmite was caused by changing hydrological patterns in SW Romania across the middle Holocene, most likely comprising local evaporation from the soil and an increase in Mediterranean moisture δ18O. Further, by extending the calculations to other speleothem records from around the entire Mediterranean basin, it appears that all eastern Mediterranean speleothems recorded a similar isotopic enrichment due to changing hydrology, whereas all changes recorded in speleothems from the western Mediterranean are fully explained by temperature variation alone. This highlights a different hydrological evolution between the two sides of the Mediterranean. Our results also demonstrate that during the 8.2 ka event, POM2 stable isotope data essentially fit the temperature-constrained isotopic variability. In the case of the 3.2 ka event, an additional climate-related hydrological factor is more evident. This implies a different rainfall pattern in the Southern Carpathian region during this event at the end of the Bronze Age

International, cooperative research in the Apuseni Mountains of western Romania

In May of 2006, nine American scientists and cavers from the Karst Research Group at the University of South Florida traveled to western Romania to attend and present at an international conference on records of climate change in caves in the historic Roman town of Baile Hurculane. The conference, co-sponsored by the “Emil Racoviţă” Speleological Institute of Romania and the Karst Waters Institute, drew more than 100 experts in the field of climate change and karst, and was a wonderful time spent alongside the thermal springs and Austro-Hungarian bathhouses nestled within the massive limestone canyon of the Cerna River. Following the conference and post-conference field trips in early June of 2006, six members of the American team joined with several Romanian colleagues to conduct paleoclimate research in the caves of the Apuseni Mountains of Transylvania. A follow-up trip in July of 2007 by a smaller research team completed the projects started the previous year. The NSS provided partial funding for the work in both 2006 and 2007 though an International Participation Grant. The Romanian Science Foundation and the Romanian Ministry of Education and Research provided much of the remaining funds

High Frequency Pulsatile Electromagnetic Fields and Ultrasound Pulsatile Fields Impact on Germination Dynamic at Ocimum basilicum L. and O. basilicum var. purpurascens Benth., Observed with Open Source Software

Basil (Ocimum sp.), generally knowned as 'king of herbs' due to its pharmaceutical and culinary properties, is considered to be a native plant derived from Africa and Asia. Ocimum sp. grows in tropical and sub-tropical regions with more than 50 species knowned till present time. Germination percent of Ocimum sp. is considered to be between 85-95%. Even though Ocimum sp. are considered to have fast germination velocity index (GVI), short mean germination time (MGT) and increased seedling vigor index (SVI) values, their experimental monitoring is done with specialized software's that are expensive. Low cost scientific solutions are keen on open source software germination protocols. For observing the accuracy of open source C.A.D. software's Ocimum sp. seeds where submitted to high frequency pulsatile electromagnetic fields (300 impulses/3 peak penetrance - 293 W) and ultrasound pulsatile fields (1/2 pulses by 0.5 W/cm2). All sequence images where taken using a positive/negative photo filter enhancing differences in seed development. At the end of the experiment all images where transformed into vector formats (dwg). On the dwg extension, selective free plug-ins such as Face Centroid and Area Properties help to collect data like seed development on X/Y scale, area, perimeter, no. of germinated seeds, length of seedling root, hypocotyl length

Using a quantum dot as a high-frequency shot noise detector

We present the experimental realization of a Quantum Dot (QD) operating as a high-frequency noise detector. Current fluctuations produced in a nearby Quantum Point Contact (QPC) ionize the QD and induce transport through excited states. The resulting transient current through the QD represents our detector signal. We investigate its dependence on the QPC transmission and voltage bias. We observe and explain a quantum threshold feature and a saturation in the detector signal. This experimental and theoretical study is relevant in understanding the backaction of a QPC used as a charge detector.Comment: 4 pages, 4 figures, accepted for publication in Physical Review Letter