3,888 research outputs found
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
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
Monolayer Molybdenum Disulfide Nanoribbons with High Optical Anisotropy
Two-dimensional Molybdenum Disulfide (MoS2) has shown promising prospects for
the next generation electronics and optoelectronics devices. The monolayer MoS2
can be patterned into quasi-one-dimensional anisotropic MoS2 nanoribbons
(MNRs), in which theoretical calculations have predicted novel properties.
However, little work has been carried out in the experimental exploration of
MNRs with a width of less than 20 nm where the geometrical confinement can lead
to interesting phenomenon. Here, we prepared MNRs with width between 5 nm to 15
nm by direct helium ion beam milling. High optical anisotropy of these MNRs is
revealed by the systematic study of optical contrast and Raman spectroscopy.
The Raman modes in MNRs show strong polarization dependence. Besides that the
E' and A'1 peaks are broadened by the phonon-confinement effect, the modes
corresponding to singularities of vibrational density of states are activated
by edges. The peculiar polarization behavior of Raman modes can be explained by
the anisotropy of light absorption in MNRs, which is evidenced by the polarized
optical contrast. The study opens the possibility to explore
quasione-dimensional materials with high optical anisotropy from isotropic 2D
family of transition metal dichalcogenides
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
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
Inhibitory Effect of Curcumol on Jak2-STAT Signal Pathway Molecules of Fibroblast-Like Synoviocytes in Patients with Rheumatoid Arthritis
Hyperplasia of synovial membrane in rheumatoid arthritis (RA) is a critical pathological foundation for inducing articular injury. The janus kinase and signal transducer and activator of transcription (Jak-STAT) pathway plays a critical role in synovial membrane proliferation induced by platelet-derived growth factor (PDGF). To explore the anti-cell proliferation mechanism of curcumol, a pure monomer extracted from Chinese medical plant zedoary rhizome, the changes of Jak2-STAT1/3 signal pathway-related molecules in synoviocytes were observed in vitro. In this study, the fibroblast-like synoviocytes (FLS) in patients with RA were collected and cultured. The following parameters were measured: cell proliferation (WST-1 assay), cell cycles (fluorescence-activated cell sorting, FACS), STAT1 and STAT3 activities (electrophoretic mobility shift assay, EMSA), and the protein expressions of phosphorylated Jak2, STAT1, and STAT3 (Western blot). It was shown that curcumol could inhibit the RA-FLS proliferation and DNA synthesis induced by PDGF-BB in a dose-dependent manner in vitro. The transcription factors activities of STAT1 and STAT3 were obviously elevated after PDGF-BB stimulation (P < 0.05). Super-shift experiments identified the STAT1 or STAT3 proteins in the complex. Furthermore, the different concentration curcumol could downregulate the DNA binding activities of STAT1 and STAT3 (P < 0.05) and inhibit the phosphorylation of Jak2 while it had no effect on the protein expressions of STAT1 and STAT3. Positive correlations were found between changes of cell proliferation and DNA-binding activities of STAT1 and STAT3, respectively (P < 0.01). In conclusion, curcumol might suppress the FLS proliferation and DNA synthesis induced by PDGF-BB through attenuating Jak2 phosphorylation, downregulating STAT1 and STAT3 DNA-binding activities, which could provide theoretical foundation for clinical treatment of RA
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