403 research outputs found
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
SH-TM mathematical analogy for the two-layer case. A magnetotellurics application
The same mathematical formalism of the wave equation can be used to describe anelastic and electromagnetic wave propagation. In this work, we obtain the mathematical analogy for the reflection/refraction (transmission) problem of two layers, considering the presence of anisotropy and attenuation -- viscosity in the viscoelastic case and resistivity in the electromagnetic case. The analogy is illustrated for SH (shear-horizontally polarised) and TM (transverse-magnetic) waves. In particular, we illustrate examples related to the magnetotelluric method applied to geothermal systems and consider the effects of anisotropy. The solution is tested with the classical solution for stratified isotropic media
Microorganisms associated with Elaeis guineensis Jacq. fruits and theirpotential to produce lipase.
Coherent oscillations in a superconducting tunable flux qubit manipulated without microwaves
We experimentally demonstrate the coherent oscillations of a tunable
superconducting flux qubit by manipulating its energy potential with a
nanosecond-long pulse of magnetic flux. The occupation probabilities of two
persistent current states oscillate at a frequency ranging from 6 GHz to 21
GHz, tunable via the amplitude of the flux pulse. The demonstrated operation
mode allows to realize quantum gates which take less than 100 ps time and are
thus much faster compared to other superconducting qubits. An other advantage
of this type of qubit is its insensitivity to both thermal and magnetic field
fluctuations.Comment: 5 pages, 5 figure
A detailed study of the rise phase of a long duration X-ray flare in the young star TWA 11B
We analyzed a long duration flare observed in a serendipitous XMM-Newton
detection of the M star CD-39 7717B (TWA 11B), member of the young stellar
association TW Hya (~ 8 Myr). Only the rise phase (with a duration of ~ 35 ks)
and possibly the flare peak were observed. We took advantage of the high
count-rate of the X-ray source to carry out a detailed analysis of its spectrum
during the whole exposure. After a careful analysis, we interpreted the rise
phase as resulting from the ignition of a first group of loops (event A) which
triggered a subsequent two-ribbon flare (event B). Event A was analyzed using a
single-loop model, while a two-ribbon model was applied for event B. Loop
semi-lengths of ~ 4 R* were obtained. Such large structures had been previously
observed in very young stellar objects (~ 1 - 4 Myr). This is the first time
that they have been inferred in a slightly more evolved star. The fluorescent
iron emission line at 6.4 keV was detected during event B. Since TWA 11B seems
to have no disk, the most plausible explanation found for its presence in the
X-ray spectrum of this star is collisional - or photo- ionization. As far as we
are concerned, this is only the third clear detection of Fe photospheric
fluorescence in stars other than the Sun.Comment: Accepted for publication in ApJ. 15 pages, 9 figure
Juvenile Chinook salmon use of sandbar willows in a large-scale, simulated riparian floodplain: microhabitat and energetics
Possible observation of parametrically amplified coherent phasons in K0.3MoO3 using time-resolved extreme-ultraviolet ARPES
We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) in the
Extreme Ultraviolet (EUV) to measure the time- and momentum-dependent
electronic structure of photo-excited K0.3MoO3. Prompt depletion of the Charge
Density Wave (CDW) condensate launches coherent oscillations of the amplitude
mode, observed as a 1.7-THz-frequency modulation of the bonding band position.
In contrast, the anti-bonding band oscillates at about half this frequency. We
attribute these oscillations to coherent excitation of phasons via parametric
amplification of phase fluctuations.Comment: 4 figure
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