10,806 research outputs found
Superconducting tunable flux qubit with direct readout scheme
We describe a simple and efficient scheme for the readout of a tunable flux
qubit, and present preliminary experimental tests for the preparation,
manipulation and final readout of the qubit state, performed in incoherent
regime at liquid Helium temperature. The tunable flux qubit is realized by a
double SQUID with an extra Josephson junction inserted in the large
superconducting loop, and the readout is performed by applying a current ramp
to the junction and recording the value for which there is a voltage response,
depending on the qubit state. This preliminary work indicates the feasibility
and efficiency of the scheme.Comment: 10 pages, 5 figure
Spectroscopic characterization of graphene films grown on Pt (111) surface by chemical vapor deposition of ethylene
This work reports the peculiar properties of a graphene film prepared by the
chemical vapor deposition (CVD) of ethylene in high vacuum on a well oriented
and carefully cleaned Pt(111) crystal surface maintained at high temperature.
In-situ and ex-situ characterization techniques (low energy electron
diffraction, high resolution electron energy loss spectroscopy, scanning
electron microscopy and Raman micro-spectroscopy) used here indicate the
prevalence of single layer regions and the presence of two different
orientations of the graphene sheets with respect to the Pt(111) substrate. In
most of the deposited area evidence is found of a compressive stress for the
graphene lattice, as a net result of the growth process on a metal substrate.
This graphene film grown on Pt(111) exhibits a lower degree of order and of
homogeneity with respect to the exfoliated graphene on Si/SiO2, as it is found
generally for graphene on metals, but several characterization techniques
indicates a better quality than in previous deposition experiments on the same
metal substrate.Comment: 18 pages, 5 figures, Journal of Raman spectroscopy 201
A Practical Understanding of Preeclampsia for a Nurse in a Third World Setting
Preeclampsia is a disease of pregnancy that affects approximately 3-5% of women with child. It is one of the primary causes of mortality in mothers and babies across the globe. The exact cause, pathogenesis, or disease progression is unknown. Therefore, there is no definition of which patients are at risk for developing preeclampsia and what can work as a preventative measure. In high socioeconomic settings where there is good healthcare, standard treatment is established to manage the symptoms and decrease the progression of preeclampsia to eclampsia. However, in more rural, third-world settings of developing countries, caring for patients with preeclampsia is not a straightforward matter. Due to decreased access to health care, low economic status, and lack of education, preeclampsia is often seen yet seldom treated among this population. The discussion below addresses several possible pathophysiological processes of preeclampsia, as well as potential risk factors. The standard treatments of care are then discussed, followed by the evaluation of studies regarding alternative treatments for preeclampsia. The importance of screening pregnant women in developing nations is included. The discussion is concluded by a summary of what caring for preeclampsia in a third-world setting might look like for a missionary nurse
A tunable rf SQUID manipulated as flux and phase qubit
We report on two different manipulation procedures of a tunable rf SQUID.
First, we operate this system as a flux qubit, where the coherent evolution
between the two flux states is induced by a rapid change of the energy
potential, turning it from a double well into a single well. The measured
coherent Larmor-like oscillation of the retrapping probability in one of the
wells has a frequency ranging from 6 to 20 GHz, with a theoretically expected
upper limit of 40 GHz. Furthermore, here we also report a manipulation of the
same device as a phase qubit. In the phase regime, the manipulation of the
energy states is realized by applying a resonant microwave drive. In spite of
the conceptual difference between these two manipulation procedures, the
measured decay times of Larmor oscillation and microwave-driven Rabi
oscillation are rather similar. Due to the higher frequency of the Larmor
oscillations, the microwave-free qubit manipulation allows for much faster
coherent operations.Comment: Proceedings of Nobel Symposium "Qubits for future quantum computers",
Goeteborg, Sweden, May 25-28, 2009; to appear in Physica Script
On the generation of multipartite entangled states in Josephson architectures
We propose and analyze a scheme for the generation of multipartite entangled
states in a system of inductively coupled Josephson flux qubits. The qubits
have fixed eigenfrequencies during the whole process in order to minimize
decoherence effects and their inductive coupling can be turned on and off at
will by tuning an external control flux. Within this framework, we will show
that a W state in a system of three or more qubits can be generated by
exploiting the sequential one by one coupling of the qubits with one of them
playing the role of an entanglement mediator.Comment: 10 pages, 3 figure
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