4,417 research outputs found
Relation Between Quantum Speed Limits And Metrics On U(n)
Recently, Chau [Quant. Inform. & Comp. 11, 721 (2011)] found a family of
metrics and pseudo-metrics on -dimensional unitary operators that can be
interpreted as the minimum resources (given by certain tight quantum speed
limit bounds) needed to transform one unitary operator to another. This result
is closely related to the weighted -norm on . Here we
generalize this finding by showing that every weighted -norm on
with 1\le p \le \limitingp induces a metric and a
pseudo-metric on -dimensional unitary operators with quantum
information-theoretic meanings related to certain tight quantum speed limit
bounds. Besides, we investigate how far the correspondence between the
existence of metrics and pseudo-metrics of this type and the quantum speed
limits can go.Comment: minor amendments, 6 pages, to appear in J.Phys.
Fault-tolerant communication channel structures
Systems and techniques for implementing fault-tolerant communication channels and features in communication systems. Selected commercial-off-the-shelf devices can be integrated in such systems to reduce the cost
Dynamics of a suspended nanowire driven by an ac Josephson current in an inhomogeneous magnetic field
We consider a voltage-biased nanoelectromechanical Josephson junction, where
a suspended nanowire forms a superconducting weak-link, in an inhomogeneous
magnetic field. We show that a nonlinear coupling between the Josephson current
and the magnetic field generates a Laplace force that induces a whirling motion
of the nanowire. By performing an analytical and a numerical analysis, we
demonstrate that at resonance, the amplitude-phase dynamics of the whirling
movement present different regimes depending on the degree of inhomogeneity of
the magnetic field: time independent, periodic and chaotic. Transitions between
these regimes are also discussed.Comment: 7 pages, 5 figure
Nonfactorization in Hadronic Two-body Cabibbo-favored decays of D^0 and D^+
With the inclusion of nonfactorized amplitudes in a scheme with , we
have studied Cabibbo-favored decays of and into two-body hadronic
states involving two isospins in the final state. We have shown that it is
possible to understand the measured branching ratios and determined the sizes
and signs of nonfactorized amplitudes required.Comment: 15 pages, Late
Impact of tumour histological subtype on chemotherapy outcome in advanced oesophageal cancer.
AIM: To investigate the impact of histology on outcome in advanced oesophageal cancer treated with first-line fluoropyrimidine-based chemotherapy. METHODS: Individual patient data were pooled from three randomised phase III trials of fluoropyrimidine-based chemotherapy ± platinum/anthracycline in patients with advanced, untreated gastroesophageal adenocarcinoma or squamous cell carcinoma (SCC) randomised between 1994 and 2005. The primary endpoint was overall survival of oesophageal cancer patients according to histology. Secondary endpoints were response rates and a toxicity composite endpoint. RESULTS: Of the total 1836 randomised patients, 973 patients (53%) were eligible (707 patients with gastric cancer were excluded), 841 (86%) had adenocarcinoma and 132 (14%) had SCC. There was no significant difference in survival between patients with adenocarcinoma and SCC, with median overall survivals of 9.5 mo vs 7.6 mo (HR = 0.85, 95%CI: 0.70-1.03, P = 0.09) and one-year survivals of 38.8% vs 28.2% respectively. The overall response rate to chemotherapy was 44% for adenocarcinoma vs 33% for SCC (P = 0.01). There was no difference in the frequency of the toxicity composite endpoint between the two groups. CONCLUSION: There was no significant difference in survival between adenocarcinoma and SCC in patients with advanced oesophageal cancer treated with fluoropyrimidine-based chemotherapy despite a trend for worse survival and less chemo-sensitivity in SCC. Tolerance to treatment was similar in both groups. This analysis highlights the unmet need for SCC-specific studies in advanced oesophageal cancer and will aid in the design of future trials of targeted agents
Branching Ratio and CP Violation of B to pi pi Decays in Perturbative QCD Approach
We calculate the branching ratios and CP asymmetries for B^0 to pi^+pi^-, B^+
to pi^+pi^0 and B^0 to pi^0pi^0 decays, in a perturbative QCD approach. In this
approach, we calculate non-factorizable and annihilation type contributions, in
addition to the usual factorizable contributions. We found that the
annihilation diagram contributions are not very small as previous argument. Our
result is in agreement with the measured branching ratio of B to pi^+pi^- by
CLEO collaboration. With a non-negligible contribution from annihilation
diagrams and a large strong phase, we predict a large direct CP asymmetry in
B^0 to pi^+pi^-, and pi^0pi^0, which can be tested by the current running B
factories.Comment: Latex, 28 pages including 11 figures; added contents and figures,
corrected typo
Final-State Phases in Charmed Meson Two-Body Nonleptonic Decays
Observed decay rates indicate large phase differences among the amplitudes
for the charge states in and but
relatively real amplitudes in the charge states for . This
feature is traced using an SU(3) flavor analysis to a sign flip in the
contribution of one of the amplitudes contributing to the latter processes in
comparison with its contribution to the other two sets. This amplitude may be
regarded as an effect of rescattering and is found to be of magnitude
comparable to others contributing to charmed particle two-body nonleptonic
decays.Comment: 19 pages, latex, 4 figures, to be submitted to Phys. Rev.
CP and T violation test in neutrino oscillation
We examine how large violation of CP and T is allowed in long base line
neutrino experiments. When we attribute only the atmospheric neutrino anomaly
to neutrino oscillation we may have large CP violation effect. When we
attribute both the atmospheric neutrino anomaly and the solar neutrino deficit
to neutrino oscillation we may have a sizable T violation effect proportional
to the ratio of two mass differences; it is difficult to see CP violation since
we can't ignore the matter effect. We give a simple expression for T violation
in the presence of matter.Comment: 12 pages + 2 eps figures, Latex, In order to avoid misunderstanding
we have refined our English and rewritten the parts which might be
misleading. Several typographical errors are correcte
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