10,183 research outputs found
Studies on X(4260) and X(4660) particles
Studies on the X(4260) and X(4660) resonant states in an effective lagrangian
approach are reviewed. Using a Breit--Wigner propagator to describe their
propagation, we find that the X(4260) has a sizable coupling to the
channel, while other couplings are found to be negligible.
Besides, it couples much stronger to than to : As an approximate result for
X(4660), we obtain that the ratio of
. Finally, taking X(3872) as an example, we also point out a possible way to
extend the previous method to a more general one in the effective lagrangian
approach.Comment: Talk given by H. Q. Zheng at "Xth Quark Confinement and the Hadron
Spectrum", October 8-12, 2012, TUM Campus Garching, Munich, Germany. 6 pages,
3 figures, 3 table
Poboljšana metoda prekida razvoja i nova rješenja opće KdV jednadžbe s promjenljivim koeficijentima
In this paper, by using a new special function transform and truncated expansion method, three kinds of exact solutions of the general variable-coefficient KdV equation have been obtained. The solutions are general and they contain some exact analytical solutions, which have been given in other papersU ovom radu, primjenom posebnih pretvorbi funkcija i prekidom razvoja, postigli smo tri egzaktna rješenja opće KdV jednadžbe s varijabilnim koeficijentima. Postignuta rješenja su općenita i sadrže neka poznata analitička rješenja u drugim radovima
Minimal sets determining universal and phase-covariant quantum cloning
We study the minimal input sets which can determine completely the universal
and the phase-covariant quantum cloning machines. We find that the universal
quantum cloning machine, which can copy arbitrary input qubit equally well,
however can be determined completely by only four input states located at the
four vertices of a tetrahedron. The phase-covariant quantum cloning machine,
which can copy all qubits located on the equator of the Bloch sphere, can be
determined by three equatorial qubits with equal angular distance. These
results sharpen further the well-known results that BB84 states and six-states
used in quantum cryptography can determine completely the phase-covariant and
universal quantum cloning machines. This concludes the study of the power of
universal and phase-covariant quantum cloning, i.e., from minimal input sets
necessarily to full input sets by definition. This can simplify dramatically
the testing of whether the quantum clone machines are successful or not, we
only need to check that the minimal input sets can be cloned optimally.Comment: 7 pages, 4 figure
Quantum Cloning Machines and the Applications
No-cloning theorem is fundamental for quantum mechanics and for quantum
information science that states an unknown quantum state cannot be cloned
perfectly. However, we can try to clone a quantum state approximately with the
optimal fidelity, or instead, we can try to clone it perfectly with the largest
probability. Thus various quantum cloning machines have been designed for
different quantum information protocols. Specifically, quantum cloning machines
can be designed to analyze the security of quantum key distribution protocols
such as BB84 protocol, six-state protocol, B92 protocol and their
generalizations. Some well-known quantum cloning machines include universal
quantum cloning machine, phase-covariant cloning machine, the asymmetric
quantum cloning machine and the probabilistic quantum cloning machine etc. In
the past years, much progress has been made in studying quantum cloning
machines and their applications and implementations, both theoretically and
experimentally. In this review, we will give a complete description of those
important developments about quantum cloning and some related topics. On the
other hand, this review is self-consistent, and in particular, we try to
present some detailed formulations so that further study can be taken based on
those results.Comment: 98 pages, 12 figures, 400+ references. Physics Reports (published
online
Demonstration of Geometric Landau-Zener Interferometry in a Superconducting Qubit
Geometric quantum manipulation and Landau-Zener interferometry have been
separately explored in many quantum systems. In this Letter, we combine these
two approaches to study the dynamics of a superconducting phase qubit. We
experimentally demonstrate Landau-Zener interferometry based on the pure
geometric phases in this solid-state qubit. We observe the interference caused
by a pure geometric phase accumulated in the evolution between two consecutive
Landau-Zener transitions, while the dynamical phase is canceled out by a
spin-echo pulse. The full controllability of the qubit state as a function of
the intrinsically robust geometric phase provides a promising approach for
quantum state manipulation.Comment: 5 pages + 3 pages supplemental Materia
No-compressing of quantum phase information
We raise a general question of quantum information theory whether the quantum
phase information can be compressed and retrieved. A general qubit contains
both amplitude and phase information, while an equatorial qubit contains only a
phase information. We study whether it is possible to compress the phase
information of n equatorial qubits into m general qubits with m being less than
n, and still those information can be retrieved perfectly. We prove that this
process is not allowed by quantum mechanics.Comment: 4 pages, 1 figur
Radio sources with ultra-high polarization
A sample of 129 unresolved radio sources with ultrahigh linear polarization
(>30 per cent) has been selected from the NRAO VLA Sky Survey. Such high
average linear polarization is unusual in extragalactic sources. Higher
resolution Australia Telescope Compact Array and Very Large Array observations
confirm the high average polarization but find that most of these sources are
extended. The Sloan Digital Sky Survey spectroscopy, where available, shows
that the optical counterparts are elliptical galaxies with no detectable
emission lines. The optical spectra, radio luminosity, linear size and spectral
index of these sources are typical of radio-loud active galactic nuclei. Galaxy
counts within a 1 Mpc radius of the radio sources show that these highly
polarized sources are in environments similar to their low polarization (<2 per
cent) counterparts. Similarly, the line-of-sight environments of the ultrahigh
polarization sources are on average indistinguishable from those of the
low-polarization sources. We conclude that the extraordinarily high average
polarization must be due to intrinsic properties of the sources, such as an
extremely ordered source magnetic field, low internal thermal plasma density or
a preferential orientation of the source magnetic field perpendicular to the
line of sight.Comment: 23 pages, 15 figures, 6 tables, accepted for publication in MNRAS;
v2: some typos correcte
Unified Universal Quantum Cloning Machine and Fidelities
We present a unified universal quantum cloning machine, which combines
several different existing universal cloning machines together including the
asymmetric case. In this unified framework, the identical pure states are
projected equally into each copy initially constituted by input and one half of
the maximally entangled states. We show explicitly that the output states of
those universal cloning machines are the same. One importance of this unified
cloning machine is that the cloning procession is always the symmetric
projection which reduces dramatically the difficulties for implementation. Also
it is found that this unified cloning machine can be directly modified to the
general asymmetric case. Besides the global fidelity and the single-copy
fidelity, we also present all possible arbitrary-copy fidelities.Comment: 4 pages, 2 figure
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