161 research outputs found
Dephasing of a superconducting flux qubit
In order to gain a better understanding of the origin of decoherence in
superconducting flux qubits, we have measured the magnetic field dependence of
the characteristic energy relaxation time () and echo phase relaxation
time () near the optimal operating point of a flux qubit. We
have measured by means of the phase cycling method. At the
optimal point, we found the relation . This means
that the echo decay time is {\it limited by the energy relaxation} (
process). Moving away from the optimal point, we observe a {\it linear}
increase of the phase relaxation rate () with the applied
external magnetic flux. This behavior can be well explained by the influence of
magnetic flux noise with a spectrum on the qubit
Spectroscopy of SrRuO/Ru Junctions in Eutectic
We have investigated the tunnelling properties of the interface between
superconducting Sr2RuO4 and a single Ru inclusion in eutectic. By using a
micro-fabrication technique, we have made Sr2RuO4/Ru junctions on the eutectic
system that consists of Sr2RuO4 and Ru micro-inclusions. Such a eutectic system
exhibits surface superconductivity, called the 3-K phase. A zero bias
conductance peak (ZBCP) was observed in the 3-K phase. We propose to use the
onset of the ZBCP to delineate the phase boundary of a time-reversal symmetry
breaking state.Comment: To be published in Proc of 24th Int. Conf. on Low Temperature Physics
(LT24); 2 page
Dephasing of a superconducting flux qubit
In order to gain a better understanding of the origin of decoherence in
superconducting flux qubits, we have measured the magnetic field dependence of
the characteristic energy relaxation time () and echo phase relaxation
time () near the optimal operating point of a flux qubit. We
have measured by means of the phase cycling method. At the
optimal point, we found the relation . This means
that the echo decay time is {\it limited by the energy relaxation} (
process). Moving away from the optimal point, we observe a {\it linear}
increase of the phase relaxation rate () with the applied
external magnetic flux. This behavior can be well explained by the influence of
magnetic flux noise with a spectrum on the qubit
Vacuum Rabi oscillations in a macroscopic superconducting qubit LC oscillator system
We have observed the coherent exchange of a single energy quantum between a
flux qubit and a superconducting LC circuit acting as a quantum harmonic
oscillator. The exchange of an energy quantum is known as the vacuum Rabi
oscillations: the qubit is oscillating between the excited state and the ground
state and the oscillator between the vacuum state and the first excited state.
We have also obtained evidence of level quantization of the LC circuit by
observing the change in the oscillation frequency when the LC circuit was not
initially in the vacuum state.Comment: Submitted to Phys. Rev. Let
Phase-Coherent Dynamics of a Superconducting Flux Qubit with Capacitive-Bias Readout
We present a systematic study of the phase-coherent dynamics of a
superconducting three-Josephson-junction flux qubit. The qubit state is
detected with the integrated-pulse method, which is a variant of the pulsed
switching DC SQUID method. In this scheme the DC SQUID bias current pulse is
applied via a capacitor instead of a resistor, giving rise to a narrow
band-pass instead of a pure low-pass filter configuration of the
electromagnetic environment. Measuring one and the same qubit with both setups
allows a direct comparison. With the capacitive method about four times faster
switching pulses and an increased visibility are achieved. Furthermore, the
deliberate engineering of the electromagnetic environment, which minimizes the
noise due to the bias circuit, is facilitated. Right at the degeneracy point
the qubit coherence is limited by energy relaxation. We find two main noise
contributions. White noise is limiting the energy relaxation and contributing
to the dephasing far from the degeneracy point. 1/f-noise is the dominant
source of dephasing in the direct vicinity of the optimal point. The influence
of 1/f-noise is also supported by non-random beatings in the Ramsey and spin
echo decay traces. Numeric simulations of a coupled qubit-oscillator system
indicate that these beatings are due to the resonant interaction of the qubit
with at least one point-like fluctuator, coupled especially strongly to the
qubit.Comment: Minor changes. 21 pages, 15 figure
Allergen Delivery Inhibitors: A Rationale for Targeting Sentinel Innate Immune Signaling of Group 1 House Dust Mite Allergens through Structure-Based Protease Inhibitor Design
Diverse evidence from epidemiologic surveys and investigations into the molecular basis of allergenicity have revealed that a small cadre of “initiator” allergens promote the development of allergic diseases, such as asthma, allergic rhinitis, and atopic dermatitis. Pre-eminent among these initiators are the group 1 allergens from house dust mites (HDM). In mites, group 1 allergens function as cysteine peptidase digestive enzymes to which humans are exposed by inhalation of HDM fecal pellets. Their protease nature confers the ability to activate high gain signaling mechanisms which promote innate immune responses, leading to the persistence of allergic sensitization. An important feature of this process is that the initiator drives responses both to itself and to unrelated allergens lacking these properties through a process of collateral priming. The clinical significance of group 1 HDM allergens in disease, their serodominance as allergens, and their IgE-independent bioactivities in innate immunity make these allergens interesting therapeutic targets in the design of new small-molecule interventions in allergic disease. The attraction of this new approach is that it offers a powerful, root-cause-level intervention from which beneficial effects can be anticipated by interference in a wide range of effector pathways associated with these complex diseases. This review addresses the general background to HDM allergens and the validation of group 1 as putative targets. We then discuss structure-based drug design of the first-in-class representatives of allergen delivery inhibitors aimed at neutralizing the proteolytic effects of HDM group 1 allergens, which are essential to the development and maintenance of allergic diseases
The crossroads of tradition and modern technology: integrative approaches to studying carnivores in low density ecosystems
The study of large carnivores in semi-arid ecosystems presents inherent challenges due to their low densities, extensive home ranges, and elusive nature. We explore the potential for the synthesis of traditional knowledge (i.e. art of tracking) and modern technology to address challenges in conservation and wildlife research in these challenging environments. Our research focuses on the African lion (Panthera leo) in the Central Kalahari region of Botswana as a model system to demonstrate the potential of this integrative approach. Combining GPS tracking and traditional San trackers’ expertise, we present two case studies: (1) the individual identification of lions via a combination of tracking and footprint analysis and (2) the monitoring of territorial behavior through a combination of GPS technology (i.e. GPS collars and handheld GPS devices) and non-invasive tracking. These approaches enhance our understanding of carnivore ecology as well as support conservation efforts by offering a non-invasive, cost-effective, and highly accurate means of monitoring populations. Our findings underscore the value of merging traditional tracking skills with contemporary analytical and technological developments to offer new insights into the ecology of carnivores in challenging environments. This approach not only improves data collection accuracy and efficiency but also fosters a deeper understanding of wildlife, ensuring the conservation and sustainable management of these species. Our work advocates for the inclusion of indigenous knowledge in conservation science, highlighting its relevance and applicability across various disciplines, thereby broadening the methodologies used to study wildlife, monitor populations, and inform conservation strategies
Alphaviruses detected in mosquitoes in the North-Eastern regions of South Africa, 2014 to 2018
The prevalence and distribution of African alphaviruses such as chikungunya have increased in recent years. Therefore, a better understanding of the local distribution of alphaviruses in vectors across the African continent is important. Here, entomological surveillance was performed from 2014 to 2018 at selected sites in north-eastern parts of South Africa where alphaviruses have been identified during outbreaks in humans and animals in the past. Mosquitoes were collected using a net, CDC-light, and BG-traps. An alphavirus genus-specific nested RT-PCR was used for screening, and positive pools were confirmed by sequencing and phylogenetic analysis. We collected 64,603 mosquitoes from 11 genera, of which 39,035 females were tested. Overall, 1462 mosquito pools were tested, of which 21 were positive for alphaviruses. Sindbis (61.9%, N = 13) and Middelburg (28.6%, N = 6) viruses were the most prevalent. Ndumu virus was detected in two pools (9.5%, N = 2). No chikungunya positive pools were identified. Arboviral activity was concentrated in peri-urban, rural, and conservation areas. A range of Culicidae species, including Culex univittatus, Cx. pipiens s.l., Aedes durbanensis, and the Ae. dentatus group, were identified as potential vectors. These findings confirm the active circulation and distribution of alphaviruses in regions where human or animal infections were identified in South Africa.Environmental Biolog
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