2,141 research outputs found
Charge Qubit Storage and Its Engineered Decoherence via Microwave Cavity
We study the entanglement of the superconducting charge qubit with the
quantized electromagnetic field in a microwave cavity. It can be controlled
dynamically by a classical external field threading the SQUID within the charge
qubit. Utilizing the controllable quantum entanglement, we can demonstrate the
dynamic process of the quantum storage of information carried by charge qubit.
On the other hand, based on this engineered quantum entanglement, we can also
demonstrate a progressive decoherence of charge qubit with quantum jump due to
the coupling with the cavity field in quasi-classical state.Comment: 6 pages, 4 figure
Effective Dynamic Range in Measurements with Flash Analog-to-Digital Convertor
Flash Analog to Digital Convertor (FADC) is frequently used in nuclear and
particle physics experiments, often as the major component in big multi-channel
systems. The large data volume makes the optimization of operating parameters
necessary. This article reports a study of a method to extend the dynamic range
of an 8-bit FADC from the nominal value. By comparing the integrated
pulse area with that of a reference profile, good energy reconstruction and
event identification can be achieved on saturated events from CsI(Tl) crystal
scintillators. The effective dynamic range can be extended by at least 4 more
bits. The algorithm is generic and is expected to be applicable to other
detector systems with FADC readout.Comment: 19 pages, 1 table, 10 figure
A time-domain recursive method to analyse transient wave propagation across rock joints
The present investigation is concerned with transient wave propagation in a rock mass with a set of parallel joints by using a recursive method. According to the displacement field of a rock mass with a set of parallel joints, the interaction between four plane waves (two longitudinal-waves and two transverse-waves) and a joint is analysed first. With the displacement discontinuity model and the time shifting function, the wave propagation equation based on the recursive method in time domain for obliquely longitudinal-(P) or transverse-(S) waves across a set of parallel joints is established. The joints are assumed linearly elastic. The analytical solution obtained by the proposed method is compared with the existing results for some special cases, including oblique incidence across a single joint and normal incidence across a set of parallel joints. By verification, it is found that the solutions by the proposed method match very well with the existing methods. The applicability and limitations of the new method are then discussed for incident waves with different propertie
Scaling of Aharonov-Bohm couplings and the dynamical vacuum in gauge theories
Recent results on the vacuum polarization induced by a thin string of
magnetic flux lead us to suggest an analogue of the Copenhagen `flux spaghetti'
QCD vacuum as a possible mechanism for avoiding the divergence of perturbative
QED, thus permitting consistent completion of the full, nonperturbative theory.
The mechanism appears to operate for spinor, but not scalar, QED.Comment: 11 pages, ITP-SB-92-40, (major conceptual evolution from original
A novel quantum key distribution scheme with orthogonal product states
The general conditions for the orthogonal product states of the multi-state
systems to be used in quantum key distribution (QKD) are proposed, and a novel
QKD scheme with orthogonal product states in the 3x3 Hilbert space is
presented. We show that this protocol has many distinct features such as great
capacity, high efficiency. The generalization to nxn systems is also discussed
and a fancy limitation for the eavesdropper's success probability is reached.Comment: 4 Pages, 3 Figure
Nonrelativistic hydrogen type stability problems on nonparabolic 3-manifolds
We extend classical Euclidean stability theorems corresponding to the
nonrelativistic Hamiltonians of ions with one electron to the setting of non
parabolic Riemannian 3-manifolds.Comment: 20 pages; to appear in Annales Henri Poincar
Pulse Shape Discrimination Techniques in Scintillating CsI(Tl) Crystals
There are recent interests with CsI(Tl) scintillating crystals for Dark
Matter experiments. The key merit is the capability to differentiate nuclear
recoil (nr) signatures from the background -events due to
ambient radioactivity on the basis of their different pulse shapes. One of the
major experimental challenges is to perform such pulse shape analysis in the
statistics-limited domain where the light output is close to the detection
threshold. Using data derived from measurements with low energy 's and
nuclear recoils due to neutron elastic scatterings, it was verified that the
pulse shapes between -events are different. Several methods of
pulse shape discrimination are studied, and their relative merits are compared.
Full digitization of the pulse shapes is crucial to achieve good
discrimination. Advanced software techniques with mean time, neural network and
likelihood ratios give rise to satisfactory performance, and are superior to
the conventional Double Charge method commonly applied at higher energies.
Pulse shape discrimination becomes effective starting at a light yield of about
20 photo-electrons. This corresponds to a detection threshold of about 5 keV
electron-equivalence energy, or 4050 keV recoil kinetic energy, in realistic
experiments.Comment: 20 pages, 7 figure
Measurement of the Intrinsic Radiopurity of Cs-137/U-235/U-238/Th-232 in CsI(Tl) Crystal Scintillators
The inorganic crystal scintillator CsI(Tl) has been used for low energy
neutrino and Dark Matter experiments, where the intrinsic radiopurity is an
issue of major importance. Low-background data were taken with a CsI(Tl)
crystal array at the Kuo-Sheng Reactor Neutrino Laboratory. The pulse shape
discrimination capabilities of the crystal, as well as the temporal and spatial
correlations of the events, provide powerful means of measuring the intrinsic
radiopurity of Cs-137 as well as the U-235, U-238 and Th-232 series. The event
selection algorithms are described, with which the decay half-lives of Po-218,
Po-214, Rn-220, Po-216 and Po-212 were derived. The measurements of the
contamination levels, their concentration gradients with the crystal growth
axis, and the uniformity among different crystal samples, are reported. The
radiopurity in the U-238 and Th-232 series are comparable to those of the best
reported in other crystal scintillators. Significant improvements in
measurement sensitivities were achieved, similar to those from dedicated
massive liquid scintillator detector. This analysis also provides in situ
measurements of the detector performance parameters, such as spatial
resolution, quenching factors, and data acquisition dead time.Comment: 28 pages, 12 figure
In-Plane Magnetic Anisotropy In RF Sputtered Fe-N Thin Films
We have fabricated Fe(N) thin films with varied N2 partial pressure and
studied the microstructure, morphology, magnetic properties and resistivity by
using X-ray diffraction, atomic force microscopy, transmission electron
microscopy, vibrating-sample magnetometer and angle-resolved M-H hysteresis
Loop tracer and standard four-point probe method. In the presence of low N2
partial pressure, Fe(N) films showed a basic bcc a-Fe structure with a
preferred (110) texture. A variation of in-plane magnetic anisotropy of the
Fe(N) films was observed with the changing of N component. The evolution of
in-plane anisotropy in the films was attributed to the directional order
mechanism. Nitrogen atoms play an important role in refining the a-Fe grains
and inducing uniaxial anisotropy.Comment: 11 pages, 6 figure
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