15 research outputs found
Witnessing Macroscopic Entanglement in a Staggered Magnetic Field
We investigate macroscopic entanglement in an infinite XX spin-1/2 chain with
staggered magnetic field, B_l=B+e^{-i\pi l}b. Using single-site entropy and by
constructing an entanglement witness, we search for the existence of
entanglement when the system is at absolute zero, as well as in thermal
equilibrium. Although the role of the alternating magnetic field b is, in
general, to suppress entanglement as do B and T, we find that when T=0,
introducing b allows the existence of entanglement even when the uniform
magnetic field B is arbitrarily large. We find that the region and the amount
of entanglement in the spin chain can be enhanced by a staggered magnetic
field.Comment: Accepted for publication in Physical Review A, minor changes from
previous version. 5 pages, 3 figure
Enhancing the Detection of Natural Thermal Entanglement with Disorder
Physical systems have some degree of disorder present in them. We discuss how
to treat natural, thermal entanglement in any random macroscopic system from
which a thermodynamic witness bounded by a constant can be found. We propose
that functional many-body perturbation theory be applied to allow either a
quenched or an annealed average over the disorder to be taken. We find when
considering the example of an XX Heisenberg spin chain with a random coupling
strength, that the region of natural entanglement detected by both witnesses
can be enhanced by the disorder.Comment: 4 pages, 2 figures, accepted by Physical Review Letter
Entanglement and the Interplay between Staggered Fields and Couplings
We investigate how the interplay between a staggered magnetic field and
staggered coupling strength affects both ground state and thermal entanglement.
Upon analytically calculating thermodynamic quantities and the correlation
functions for such a system, we consider both the global Meyer-Wallach measure
of entanglement and the concurrence between pairs of spins. We discover two
quantum phase transitions present in the model and show that the quantum phase
transitions are reflected in the behaviour of the entanglement at zero
temperature. We discover that increasing the alternating field and alternating
coupling strength can actually increase the amount of entanglement present at
both zero temperature and for thermal states of the system.Comment: 10 pages, 10 figure
Concurrence in Disordered Systems
Quantum systems exist at finite temperatures and are likely to be disordered
to some level. Since applications of quantum information often rely on
entanglement, we require methods which allow entanglement measures to be
calculated in the presence of disorder at non-zero temperatures. We demonstrate
how the disorder averaged concurrence can be calculated using thermal many-body
perturbation theory. Our technique can also be applied to other entanglement
measures. To illustrate, we find the disorder averaged concurrence of an XX
spin chain. We find that concurrence can be increased by disorder in some
parameter regimes.Comment: 14 pages, 5 figure
Recent Advances in Conjugated Polymers for Light Emitting Devices
A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review
Genome-wide Analyses Identify KIF5A as a Novel ALS Gene
To identify novel genes associated with ALS, we undertook two lines of investigation. We carried out a genome-wide association study comparing 20,806 ALS cases and 59,804 controls. Independently, we performed a rare variant burden analysis comparing 1,138 index familial ALS cases and 19,494 controls. Through both approaches, we identified kinesin family member 5A (KIF5A) as a novel gene associated with ALS. Interestingly, mutations predominantly in the N-terminal motor domain of KIF5A are causative for two neurodegenerative diseases: hereditary spastic paraplegia (SPG10) and Charcot-Marie-Tooth type 2 (CMT2). In contrast, ALS-associated mutations are primarily located at the C-terminal cargo-binding tail domain and patients harboring loss-of-function mutations displayed an extended survival relative to typical ALS cases. Taken together, these results broaden the phenotype spectrum resulting from mutations in KIF5A and strengthen the role of cytoskeletal defects in the pathogenesis of ALS.Peer reviewe
Detecting entanglement with Jarzynski's equality
10.1103/PhysRevA.81.062303Physical Review A - Atomic, Molecular, and Optical Physics816-PLRA
Predominant clonal evolution leads to a close parity between gene expression profiles and subspecific phylogeny in Trypanosoma cruzi
We investigated the relationships between overall phylogenetic diversity in Trypanosoma cruzi evidenced by multilocus markers (MLEE and RAPD) on the one hand, and gene expression patterns, revealed by mRNA analysis on the other hand. Nineteen laboratory-cloned stocks representative of this parasite’s overall phylogenetic diversity and ecogeographical range were analyzed using random amplified differentially expressed sequences (RADES). The bat trypanosome T. cruzi marinkellei was taken as outgroup. The profiles obtained showed that RADES polymorphism cannot be considered as a simple subsample of general RAPD polymorphism. Indeed, many RADES bands were not present in general RAPD profiles, and vice versa. Phylogenies obtained from RADES on the one hand, and MLEE/RAPD on the other hand, were very similar. This suggests that in spite of the recent observation of hybrid genotypes and mosaic genes in T. cruzi, clonal evolution in this parasite has been preponderant enough on an evolutionary scale to carve the polymorphism on all types of DNA sequences, including expressed genes, although these genes are assumed to undergo natural selection pressure contrary to noncoding sequences and neutral polymorphisms