463 research outputs found
Coupled superconducting qudit-resonator system: Energy spectrum, state population, and state transition under microwave drive
Superconducting quantum multilevel systems coupled to resonators have recently been considered in some
applications such as microwave lasing and high-fidelity quantum logical gates. In this work, using an rf-SQUID
type phase qudit coupled to a microwave coplanar waveguide resonator, we study both theoretically and
experimentally the energy spectrum of the system when the qudit level spacings are varied around the resonator
frequency by changing the magnetic flux applied to the qudit loop. We show that the experimental result can
be well described by a theoretical model that extends from the usual two-level Jaynes-Cummings system to the
present four-level system. It is also shown that due to the small anharmonicity of the phase device a simplified
model capturing the leading state interactions fits the experimental spectra very well. Furthermore we use the
Lindblad master equation containing various relaxation and dephasing processes to calculate the level populations
in the simpler qutrit-resonator system, which allows a clear understanding of the dynamics of the system under
the microwave drive. Our results help to better understand and perform the experiments of coupled multilevel
and resonator systems and can be applied in the case of transmon or Xmon qudits having similar anharmonicity
to the present phase device.This work was supported by the Ministry of Science and Technology of China (Grants No. 2014CB921202, No. 2015CB921104, and No. 2016YFA0300601),the National Natural Science Foundation of China (Grants No. 91321208 and No. 11674380)the Key Research Program of the Chinese Academy of Sciences (Grant No. XDPB08-3)S.H. acknowledges support by the US NSF (PHY-1314861)
Observations of Coronal Mass Ejections with the Coronal Multichannel Polarimeter
The Coronal Multichannel Polarimeter (CoMP) measures not only the
polarization of coronal emission, but also the full radiance profiles of
coronal emission lines. For the first time, CoMP observations provide
high-cadence image sequences of the coronal line intensity, Doppler shift and
line width simultaneously in a large field of view. By studying the Doppler
shift and line width we may explore more of the physical processes of CME
initiation and propagation. Here we identify a list of CMEs observed by CoMP
and present the first results of these observations. Our preliminary analysis
shows that CMEs are usually associated with greatly increased Doppler shift and
enhanced line width. These new observations provide not only valuable
information to constrain CME models and probe various processes during the
initial propagation of CMEs in the low corona, but also offer a possible
cost-effective and low-risk means of space weather monitoring.Comment: 6 figures. Will appear in the special issue of Coronal Magnetism,
Sol. Phy
Using Host-Guest Chemistry to Tune the Kinetics of Morphological Transitions Undertaken by Block Copolymer Vesicles
Host-guest chemistry is exploited to tune the rate at which block copolymer vesicles undergo morphological transitions. More specifically, a concentrated aqueous dispersion of poly(glycerol monomethacrylate-co-glycidyl methacrylate)-poly(2-hydroxypropyl methacrylate) [P(GMA-co-GlyMA)-PHPMA] diblock copolymer vesicles was prepared via polymerization-induced self-assembly (PISA). The epoxy groups in the GlyMA residues were ring-opened using a primary amine-functionalized β-cyclodextrin (NH 2 -β-CD) in order to prepare β-CD-decorated vesicles. Addition of azobenzene-methoxypoly(ethylene glycol) (azo-mPEG) to such vesicles results in specific binding of this water-soluble macromolecular reagent to the β-CD groups on the hydrophilic P(GMA-co-GlyMA) stabilizer chains. Such host-guest chemistry induces a morphological transition from vesicles to worms and/or spheres. Furthermore, the rate of this morphological transition can be tuned by UV/visible-light irradiation and/or guest molecule competition. This novel molecular recognition strategy offers considerable scope for the design of new stimulus-responsive diblock copolymer vesicles for targeted delivery and controlled release of cargoes
CP violating neutrino oscillation and uncertainties in Earth matter density
We propose a statistical formulation to estimate possible errors in long
baseline neutrino oscillation experiments caused by uncertainties in the Earth
matter density. A quantitative investigation of the effect is made on the CP
asymmetry in future neutrino factory experiments.Comment: Latex, 10 pages, 5 figure
Pulsar-wind nebulae and magnetar outflows: observations at radio, X-ray, and gamma-ray wavelengths
We review observations of several classes of neutron-star-powered outflows:
pulsar-wind nebulae (PWNe) inside shell supernova remnants (SNRs), PWNe
interacting directly with interstellar medium (ISM), and magnetar-powered
outflows. We describe radio, X-ray, and gamma-ray observations of PWNe,
focusing first on integrated spectral-energy distributions (SEDs) and global
spectral properties. High-resolution X-ray imaging of PWNe shows a bewildering
array of morphologies, with jets, trails, and other structures. Several of the
23 so far identified magnetars show evidence for continuous or sporadic
emission of material, sometimes associated with giant flares, and a few
possible "magnetar-wind nebulae" have been recently identified.Comment: 61 pages, 44 figures (reduced in quality for size reasons). Published
in Space Science Reviews, "Jets and Winds in Pulsar Wind Nebulae, Gamma-ray
Bursts and Blazars: Physics of Extreme Energy Release
Probing the Role of Magnetic-Field Variations in NOAA AR 8038 in Producing Solar Flare and CME on 12 May 1997
We carried out a multi-wavelength study of a CME and a medium-size 1B/C1.3
flare occurring on 12 May 1997. We present the investigation of magnetic-field
variations in the NOAA Active Region 8038 which was observed on the Sun during
7--16 May 1997. Analyses of H{\alpha} filtergrams and MDI/SOHO magnetograms
revealed continual but discrete surge activity, and emergence and cancellation
of flux in this active region. The movie of these magnetograms revealed two
important results that the major opposite polarities of pre-existing region as
well as in the emerging flux region (EFR) were approaching towards each other
and moving magnetic features (MMF) were ejecting out from the major north
polarity at a quasi-periodicity of about ten hrs during 10--13 May 1997. These
activities were probably caused by the magnetic reconnection in the lower
atmosphere driven by photospheric convergence motions, which were evident in
magnetograms. The magnetic field variations such as flux, gradient, and sunspot
rotation revealed that free energy was slowly being stored in the corona. The
slow low-layer magnetic reconnection may be responsible for this storage and
the formation of a sigmoidal core field or a flux rope leading to the eventual
eruption. The occurrence of EUV brightenings in the sigmoidal core field prior
to the rise of a flux rope suggests that the eruption was triggered by the
inner tether-cutting reconnection, but not the external breakout reconnection.
An impulsive acceleration revealed from fast separation of the H{\alpha}
ribbons of the first 150 seconds suggests the CME accelerated in the inner
corona, which is consistent with the temporal profile of the reconnection
electric field. In conclusion, we propose a qualitative model in view of
framework of a solar eruption involving, mass ejections, filament eruption,
CME, and subsequent flare.Comment: 8 figures, accepted for publication in Solar Physic
Measurements of the Mass and Full-Width of the Meson
In a sample of 58 million events collected with the BES II detector,
the process J/ is observed in five different decay
channels: , , (with ), (with
) and . From a combined fit of all five
channels, we determine the mass and full-width of to be
MeV/ and
MeV/.Comment: 9 pages, 2 figures and 4 table. Submitted to Phys. Lett.
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta
Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector,
the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are
measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and
(7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure
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