27,680 research outputs found
Anyonic interferometry without anyons: How a flux qubit can read out a topological qubit
Proposals to measure non-Abelian anyons in a superconductor by quantum
interference of vortices suffer from the predominantly classical dynamics of
the normal core of an Abrikosov vortex. We show how to avoid this obstruction
using coreless Josephson vortices, for which the quantum dynamics has been
demonstrated experimentally. The interferometer is a flux qubit in a Josephson
junction circuit, which can nondestructively read out a topological qubit
stored in a pair of anyons --- even though the Josephson vortices themselves
are not anyons. The flux qubit does not couple to intra-vortex excitations,
thereby removing the dominant restriction on the operating temperature of
anyonic interferometry in superconductors.Comment: 7 pages, 3 figures; Added an Appendix on parity-protected
single-qubit rotations; problem with Figure 3 correcte
Entanglement detection beyond the CCNR criterion for infinite-dimensions
In this paper, in terms of the relation between the state and the reduced
states of it, we obtain two inequalities which are valid for all separable
states in infinite-dimensional bipartite quantum systems. One of them provides
an entanglement criterion which is strictly stronger than the computable
cross-norm or realignment (CCNR) criterion.Comment: 11 page
The Dynamical Yang-Baxter Relation and the Minimal Representation of the Elliptic Quantum Group
In this paper, we give the general forms of the minimal matrix (the
elements of the -matrix are numbers) associated with the Boltzmann
weights of the interaction-round-a-face (IRF) model and the minimal
representation of the series elliptic quantum group given by Felder
and Varchenko. The explicit dependence of elements of -matrices on spectral
parameter are given. They are of five different forms (A(1-4) and B). The
algebra for the coefficients (which do not depend on ) are given. The
algebra of form A is proved to be trivial, while that of form B obey
Yang-Baxter equation (YBE). We also give the PBW base and the centers for the
algebra of form B.Comment: 23 page
Eigenvalues of Ruijsenaars-Schneider models associated with root system in Bethe ansatz formalism
Ruijsenaars-Schneider models associated with root system with a
discrete coupling constant are studied. The eigenvalues of the Hamiltonian are
givein in terms of the Bethe ansatz formulas. Taking the "non-relativistic"
limit, we obtain the spectrum of the corresponding Calogero-Moser systems in
the third formulas of Felder et al [20].Comment: Latex file, 25 page
Necessary and sufficient conditions for local creation of quantum discord
We show that a local channel cannot create quantum discord (QD) for zero QD
states of size if and only if either it is a completely decohering
channel or it is a nontrivial isotropic channel. For the qubit case this
propertiy is additionally characteristic to the completely decohering channel
or the commutativity-preserving unital channel. In particular, the exact forms
of the completely decohering channel and the commutativity-preserving unital
qubit channel are proposed. Consequently, our results confirm and improve the
conjecture proposed by X. Hu et al. for the case of and improve the
result proposed by A. Streltsov et al. for the qubit case. Furthermore, it is
shown that a local channel nullifies QD in any state if and only if it is a
completely decohering channel. Based on our results, some protocols of quantum
information processing issues associated with QD, especially for the qubit
case, would be experimentally accessible.Comment: 8 page
Calibration of LAMOST Stellar Surface Gravities Using the Kepler Asteroseismic Data
Asteroseismology is a powerful tool to precisely determine the evolutionary
status and fundamental properties of stars. With the unprecedented precision
and nearly continuous photometric data acquired by the NASA Kepler mission,
parameters of more than 10 stars have been determined nearly consistently.
However, most studies still use photometric effective temperatures (Teff) and
metallicities ([Fe/H]) as inputs, which are not sufficiently accurate as
suggested by previous studies. We adopted the spectroscopic Teff and [Fe/H]
values based on the LAMOST low-resolution spectra (R~1,800), and combined them
with the global oscillation parameters to derive the physical parameters of a
large sample of stars. Clear trends were found between {\Delta}logg(LAMOST -
seismic) and spectroscopic Teff as well as logg, which may result in an
overestimation of up to 0.5 dex for the logg of giants in the LAMOST catalog.
We established empirical calibration relations for the logg values of dwarfs
and giants. These results can be used for determining the precise distances to
these stars based on their spectroscopic parameters.Comment: 22 pages, 13 figures and 3 tables, accepted for publication in
Astronomical Journal. Table 3 is available at
http://lwang.info/research/kepler_lamost
Geodesic scattering by surface deformations of a topological insulator
We consider the classical ballistic dynamics of massless electrons on the
conducting surface of a three-dimensional topological insulator, influenced by
random variations of the surface height. By solving the geodesic equation and
the Boltzmann equation in the limit of shallow deformations, we obtain the
scattering cross section and the conductivity {\sigma}, for arbitrary
anisotropic dispersion relation. At large surface electron densities n this
geodesic scattering mechanism (with {\sigma} propto sqrt{n}) is more effective
at limiting the surface conductivity than electrostatic potential scattering.Comment: 9 pages, 5 figure
Cyber Inference System for Substation Anomalies Against Alter-and-Hide Attacks
Alarms reported to energy control centers are an indication of abnormal events caused by either weather interruptions, system errors, or possibly intentional anomalies. Although these initiating events are random, e.g., faults on transmission lines struck by lightning, the existence of electronically altered measurements may implicate the process to identify root causes of abnormal events. This paper is concerned with alter-andhide (AaH) attacks by tampering the actual measurements to normal states with the background of disruptive switching actions that hide the true values of local events from operators at the control center. A cyber inference system (CyIS) framework is proposed to synthesize all sequential, missing, or altered alarms of related substations against AaH attacks. The stochastic nature of such attack events is modeled with probabilities as an integer programming problem with multiple scenarios. The proposed method is utilized to verify alarm scenarios for a conclusion of the potential AaH attacks on the substations.postprin
Ettingshausen effect due to Majorana modes
The presence of Majorana zero-energy modes at vortex cores in a topological
superconductor implies that each vortex carries an extra entropy , given
by , that is independent of temperature. By utilizing this
special property of Majorana modes, the edges of a topological superconductor
can be cooled (or heated) by the motion of the vortices across the edges. As
vortices flow in the transverse direction with respect to an external imposed
supercurrent, due to the Lorentz force, a thermoelectric effect analogous to
the Ettingshausen effect is expected to occur between opposing edges. We
propose an experiment to observe this thermoelectric effect, which could
directly probe the intrinsic entropy of Majorana zero-energy modes.Comment: 16 pages, 3 figure
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