1,727 research outputs found
Production of J/-Particles at RHIC and LHC energies: An Alternative `Psi'-chology
We attempt here to understand successfully some crucial aspects of
-production in some high energy nuclear collisions in the light of a
non-standard framework outlined in the text. It is found that the results
arrived at with this main working approach here is fairly in good agreement
with both the measured data and the results obtained on the basis of some other
models of the `standard' variety. Impact and implications of this comparative
study have also been precisely highlighted in the end.Comment: 14 pages, 7 figures, to appear in Open Journal of Microphysics. arXiv
admin note: substantial text overlap with arXiv:0906.2612, arXiv:1110.5582,
and overlap with arXiv:1103.6269, arXiv:1007.451
Quantum rotor theory of spinor condensates in tight traps
In this work, we theoretically construct exact mappings of many-particle
bosonic systems onto quantum rotor models. In particular, we analyze the rotor
representation of spinor Bose-Einstein condensates. In a previous work it was
shown that there is an exact mapping of a spin-one condensate of fixed particle
number with quadratic Zeeman interaction onto a quantum rotor model. Since the
rotor model has an unbounded spectrum from above, it has many more eigenstates
than the original bosonic model. Here we show that for each subset of states
with fixed spin F_z, the physical rotor eigenstates are always those with
lowest energy. We classify three distinct physical limits of the rotor model:
the Rabi, Josephson, and Fock regimes. The last regime corresponds to a
fragmented condensate and is thus not captured by the Bogoliubov theory. We
next consider the semiclassical limit of the rotor problem and make connections
with the quantum wave functions through use of the Husimi distribution
function. Finally, we describe how to extend the analysis to higher-spin
systems and derive a rotor model for the spin-two condensate. Theoretical
details of the rotor mapping are also provided here.Comment: 10 pages, 2 figure
Genome landscapes and bacteriophage codon usage
Across all kingdoms of biological life, protein-coding genes exhibit unequal
usage of synonmous codons. Although alternative theories abound, translational
selection has been accepted as an important mechanism that shapes the patterns
of codon usage in prokaryotes and simple eukaryotes. Here we analyze patterns
of codon usage across 74 diverse bacteriophages that infect E. coli, P.
aeruginosa and L. lactis as their primary host. We introduce the concept of a
`genome landscape,' which helps reveal non-trivial, long-range patterns in
codon usage across a genome. We develop a series of randomization tests that
allow us to interrogate the significance of one aspect of codon usage, such a
GC content, while controlling for another aspect, such as adaptation to
host-preferred codons. We find that 33 phage genomes exhibit highly non-random
patterns in their GC3-content, use of host-preferred codons, or both. We show
that the head and tail proteins of these phages exhibit significant bias
towards host-preferred codons, relative to the non-structural phage proteins.
Our results support the hypothesis of translational selection on viral genes
for host-preferred codons, over a broad range of bacteriophages.Comment: 9 Color Figures, 5 Tables, 53 Reference
Engineering and manipulating topological qubits in 1D quantum wires
We investigate the Josephson effect in TNT and NTN junctions, consisting of
topological (T) and normal (N) phases of semiconductor-superconductor 1D
heterostructures in the presence of a Zeeman field. A key feature of our setup
is that, in addition to the variation of the phase of the superconducting order
parameter, we allow the orientation of the magnetic field to change along the
junction. We find a novel magnetic contribution to the Majorana Josephson
coupling that permits the Josephson current to be tuned by changing the
orientation of the magnetic field along the junction. We also predict that a
spin current can be generated by a finite superconducting phase difference,
rendering these materials potential candidates for spintronic applications.
Finally, this new type of coupling not only constitutes a unique fingerprint
for the existence of Majorana bound states but also provides an alternative
pathway for manipulating and braiding topological qubits in networks of wires.Comment: references and a note were added in v2; 6 pages, 2 figures; v1 had
been submitted for the ICM2012 proceedings on the 31st of May 201
Top-transmon: hybrid superconducting qubit for parity-protected quantum computation
Qubits constructed from uncoupled Majorana fermions are protected from
decoherence, but to perform a quantum computation this topological protection
needs to be broken. Parity-protected quantum computation breaks the protection
in a minimally invasive way, by coupling directly to the fermion parity of the
system --- irrespective of any quasiparticle excitations. Here we propose to
use a superconducting charge qubit in a transmission line resonator (a socalled
transmon) to perform parity-protected rotations and read-out of a topological
(top) qubit. The advantage over an earlier proposal using a flux qubit is that
the coupling can be switched on and off with exponential accuracy, promising a
reduced sensitivity to charge noise.Comment: 7 pages, 5 figure
Non-Abelian statistics and topological quantum information processing in 1D wire networks
Topological quantum computation provides an elegant way around decoherence,
as one encodes quantum information in a non-local fashion that the environment
finds difficult to corrupt. Here we establish that one of the key
operations---braiding of non-Abelian anyons---can be implemented in
one-dimensional semiconductor wire networks. Previous work [Lutchyn et al.,
arXiv:1002.4033 and Oreg et al., arXiv:1003.1145] provided a recipe for driving
semiconducting wires into a topological phase supporting long-sought particles
known as Majorana fermions that can store topologically protected quantum
information. Majorana fermions in this setting can be transported, created, and
fused by applying locally tunable gates to the wire. More importantly, we show
that networks of such wires allow braiding of Majorana fermions and that they
exhibit non-Abelian statistics like vortices in a p+ip superconductor. We
propose experimental setups that enable the Majorana fusion rules to be probed,
along with networks that allow for efficient exchange of arbitrary numbers of
Majorana fermions. This work paves a new path forward in topological quantum
computation that benefits from physical transparency and experimental realism.Comment: 6 pages + 17 pages of Supp. Mat.; 10 figures. Supp. Mat. has doubled
in size to establish results more rigorously; many other improvements as wel
Topological orbital ladders
We unveil a topological phase of interacting fermions on a two-leg ladder of
unequal parity orbitals, derived from the experimentally realized double-well
lattices by dimension reduction. topological invariant originates simply
from the staggered phases of -orbital quantum tunneling, requiring none of
the previously known mechanisms such as spin-orbit coupling or artificial gauge
field. Another unique feature is that upon crossing over to two dimensions with
coupled ladders, the edge modes from each ladder form a parity-protected flat
band at zero energy, opening the route to strongly correlated states controlled
by interactions. Experimental signatures are found in density correlations and
phase transitions to trivial band and Mott insulators.Comment: 12 pages, 5 figures, Revised title, abstract, and the discussion on
Majorana numbe
- …