25,645 research outputs found
Edge Excitations and Non-Abelian Statistics in the Moore-Read State: A Numerical Study in the Presence of Coulomb Interaction and Edge Confinement
We study the ground state and low-energy excitations of fractional quantum
Hall systems on a disk at filling fraction , with Coulomb
interaction and background confining potential. We find the Moore-Read ground
state is stable within a finite but narrow window in parameter space. The
corresponding low-energy excitations contain a fermionic branch and a bosonic
branch, with widely different velocities. A short-range repulsive potential can
stabilize a charge quasihole at the center, leading to a different edge
excitation spectrum due to the change of boundary conditions for Majorana
fermions, clearly indicating the non-Abelian nature of the quasihole.Comment: 4 pages, 3 figures. New version shortened for PRL. Corrected typo
Constructing Functional Braids for Low-Leakage Topological Quantum Computing
We discuss how to significantly reduce leakage errors in topological quantum
computation by introducing an irrelevant error in phase, using the construction
of a CNOT gate in the Fibonacci anyon model as a concrete example. To be
specific, we construct a functional braid in a six-anyon Hilbert space that
exchanges two neighboring anyons while conserving the encoded quantum
information. The leakage error is for a braid of 100
interchanges of anyons. Applying the braid greatly reduces the leakage error in
the construction of generic controlled-rotation gates.Comment: 5 pages, 4 figures, updated, accepeted by Phys. Rev.
Caging phenomena in reactions: Femtosecond observation of coherent, collisional confinement
We report striking observations of coherent caging of iodine, above the B state dissociation threshold, by single collisions with rare gas atoms at room-temperature. Despite the random nature of the solute–solvent interaction, the caged population retains coherence of the initially prepared unbound wave packet. We discuss some new concepts regarding dynamical coherent caging and the one-atom cage effect
Dynamics of ligand substitution in labile cobalt complexes resolved by ultrafast T-jump
Ligand exchange of hydrated metal complexes is common in chemical and biological systems. Using the ultrafast T-jump, we examined this process, specifically the transformation of aqua cobalt (II) complexes to their fully halogenated species. The results reveal a stepwise mechanism with time scales varying from hundreds of picoseconds to nanoseconds. The dynamics are significantly faster when the structure is retained but becomes rate-limited when the octahedral-to-tetrahedral structural change bottlenecks the transformation. Evidence is presented, from bimolecular kinetics and energetics (enthalpic and entropic), for a reaction in which the ligand assists the displacement of water molecules, with the retention of the entering ligand in the activated state. The reaction time scale deviates by one to two orders of magnitude from that of ionic diffusion, suggesting the involvement of a collisional barrier between the ion and the much larger complex
Observation Of Turbulent Intermittency Scaling With Magnetic Helicity In An MHD Plasma Wind Tunnel
The intermittency in turbulent magnetic field fluctuations has been observed to scale with the amount of magnetic helicity injected into a laboratory plasma. An unstable spheromak injected into the MHD wind tunnel of the Swarthmore Spheromak Experiment displays turbulent magnetic and plasma fluctuations as it relaxes into a Taylor state. The level of intermittency of this turbulence is determined by finding the flatness of the probability distribution function of increments for magnetic pickup coil fluctuations B(t). The intermittency increases with the injected helicity, but spectral indices are unaffected by this variation. While evidence is provided which supports the hypothesis that current sheets and reconnection sites are related to the generation of this intermittent signal, the true nature of the observed intermittency remains unknown
Scaling and non-Abelian signature in fractional quantum Hall quasiparticle tunneling amplitude
We study the scaling behavior in the tunneling amplitude when quasiparticles
tunnel along a straight path between the two edges of a fractional quantum Hall
annulus. Such scaling behavior originates from the propagation and tunneling of
charged quasielectrons and quasiholes in an effective field analysis. In the
limit when the annulus deforms continuously into a quasi-one-dimensional ring,
we conjecture the exact functional form of the tunneling amplitude for several
cases, which reproduces the numerical results in finite systems exactly. The
results for Abelian quasiparticle tunneling is consistent with the scaling
anaysis; this allows for the extraction of the conformal dimensions of the
quasiparticles. We analyze the scaling behavior of both Abelian and non-Abelian
quasiparticles in the Read-Rezayi Z_k-parafermion states. Interestingly, the
non-Abelian quasiparticle tunneling amplitudes exhibit nontrivial k-dependent
corrections to the scaling exponent.Comment: 16 pages, 4 figure
A novel regulatory pathway of Desmoglein-3 in keratinocyte stress response
The desmosomal cadherin Desmoglein-3 (Dsg3) is a core adhesion component in desmosome junctions that occur with high frequency in the stratified squamous epithelial membrane lining the skin and mucous membrane. Dsg3 is identified as a major target of the circulating autoantibodies in Pemphigus Vulgaris (PV), an autoimmune blistering skin disease, and many signaling pathways have been demonstrated to be activated by PV-IgG targeting Dsg3, highlighting its role as a surface regulator in cell signaling. A recent study has revealed an unprecedented role of Dsg3 in the suppression of p53 and shows dysfunction of this pathway in PV. Furthermore, reciprocal crosstalk between p53 and yes-associated protein (YAP) downstream of Dsg3 has been observed in keratinocytes in which increased YAP expression causes suppression of p53 or vice versa. Both p53 and YAP are the crucial nuclear transcription factors involved in regulating cell fate decision, adaptation and tissue integrity in response to environmental and biological cues and are mutually exclusive in human cancer. In this review, we discuss Dsg3 signaling role in keratinocyte response to stress signals, with the highlight on our recent findings of the Dsg3/p53 pathway in the control of cell proliferation and tissue homeostasis, including the DNA integrity, beyond its function in cell-cell adhesion
Possible origin of the 0.5 plateau in the ballistic conductance of quantum point contacts
A non-equilibrium Green function formalism (NEGF) is used to study the
conductance of a side-gated quantum point contact (QPC) in the presence of
lateral spin-orbit coupling (LSOC). A small difference of bias voltage between
the two side gates (SGs) leads to an inversion asymmetry in the LSOC between
the opposite edges of the channel. In single electron modeling of transport,
this triggers a spontaneous but insignificant spin polarization in the QPC.
However, the spin polarization of the QPC is enhanced substantially when the
effect of electron-electron interaction is included. The spin polarization is
strong enough to result in the occurrence of a conductance plateau at 0.5G0 (G0
= 2e2/h) in the absence of any external magnetic field. In our simulations of a
model QPC device, the 0.5 plateau is found to be quite robust and survives up
to a temperature of 40K. The spontaneous spin polarization and the resulting
magnetization of the QPC can be reversed by flipping the polarity of the source
to drain bias or the potential difference between the two SGs. These numerical
simulations are in good agreement with recent experimental results for
side-gated QPCs made from the low band gap semiconductor InAs
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