Optimal universal and state-dependent quantum cloning

We establish the best possible approximation to a perfect quantum cloning machine that produces two clones out of a single input. We analyze both universal and state-dependent cloners. The maximal fidelity of cloning is shown to be 5/6 for universal cloners. It can be achieved either by a special unitary evolution or by a teleportation scheme. We construct the optimal state-dependent cloners operating on any prescribed two nonorthogonal states and discuss their fidelities and the use of auxiliary physical resources in the process of cloning. The optimal universal cloners permit us to derive an upper bound on the quantum capacity of the depolarizing quantum channel

The High-Resolution Structures of the Neutral and the Low pH Crystals of Aminopeptidase from \u3cem\u3eAeromonas proteolytica\u3c/em\u3e

The aminopeptidase from Aeromonas proteolytica (AAP) contains two zinc ions in the active site and catalyzes the degradation of peptides. Herein we report the crystal structures of AAP at 0.95-Å resolution at neutral pH and at 1.24-Å resolution at low pH. The combination of these structures allowed the precise modeling of atomic positions, the identification of the metal bridging oxygen species, and insight into the physical properties of the metal ions. On the basis of these structures, a new putative catalytic mechanism is proposed for AAP that is likely relevant to all binuclear metalloproteases

Reversible quantum teleportation in an optical lattice

We propose a protocol, based on entanglement procedures recently suggested by [D. Jaksch et al., Phys. Rev. Lett. 82, 1975 (1999)], which allows the teleportation of an unknown state of a neutral atom in an optical lattice to another atom in another site of the lattice, without any irreversible detection.Comment: 8 pages, 3 figure

Chemoresistance of glioblastoma cancer stem cells - much more complex than expected

Glioblastomas (GBM) are a paradigm for the investigation of cancer stem cells (CSC) in solid malignancies. The susceptibility of GBM CSC to standard chemotherapeutic drugs is controversial as the existing literature presents conflicting experimental data. Here, we summarize the experimental evidence on the resistance of GBM CSC to alkylating chemotherapeutic agents, with a special focus on temozolomide (TMZ). The data suggests that CSC are neither resistant nor susceptible to chemotherapy per se. Detoxifying proteins such as O6-methylguanine-DNA-methyltransferase (MGMT) confer a strong intrinsic resistance to CSC in all studies. Extrinsic factors may also contribute to the resistance of CSC to TMZ. These may include TMZ concentrations in the brain parenchyma, TMZ dosing schemes, hypoxic microenvironments, niche factors, and the re-acquisition of stem cell properties by non-stem cells. Thus, the interaction of CSC and chemotherapy is more complex than may be expected and it is necessary to consider these factors in order to overcome chemoresistance in the patient

Host-Imposed Copper Poisoning Impacts Fungal Micronutrient Acquisition during Systemic Candida albicans Infections

This work was supported by the European Research Council (http://erc.europa.eu/: STRIFE Advanced Grant ERC-2009-AdG-249793). A.J.P.B. was also supported by the UK Biotechnology and Biological Research Council (www.bbsrc.ac.uk: Research Grants BB/F00513X/1, BB/K017365/1), the UK Medical Research Council (www.mrc.ac.uk: Programme Grant MR/M026663/1; Centre Grant MR/ N006364/1), and the Wellcome Trust (www.wellcome.ac.uk: Strategic Award 097377)Peer reviewedPublisher PD

Tomographic Quantum Cryptography: Equivalence of Quantum and Classical Key Distillation

The security of a cryptographic key that is generated by communication through a noisy quantum channel relies on the ability to distill a shorter secure key sequence from a longer insecure one. For an important class of protocols, which exploit tomographically complete measurements on entangled pairs of any dimension, we show that the noise threshold for classical advantage distillation is identical with the threshold for quantum entanglement distillation. As a consequence, the two distillation procedures are equivalent: neither offers a security advantage over the other.Comment: 4 pages, 1 figur

La imagen de lo femenino. La estatuilla antropomorfa de la Capacocha del cerro El Plomo

The Cerro El Plomo capacocha ceremony occurred at the top of a sacred peak, or Apu, situated in the Mapocho Valley, where Santiago de Chile is now located. Archaeologists believe that such an important Inca ritual was not only of a political-religious nature within the conquest of conquered valleys, but that it also functioned as a mechanism of symbolic efficacy, and as a means of achieving the ideological introduction and assimilation of the local ethnic groups that had occupied the valley before the arrival of the Incas. The use of anthropomorphic figurines as part of the ritual, like the one found in 1954 in the context of an invasion of an archaeological site by tomb robbers, highlights the standardization of symbolic material within the Inca state, as well as the distinctive identity components apparent in the design of textiles. In light of these factors, a semiotic analysis is required, based upon interpretation of the Inca foundation myth as a political and social strategy, as well as that same myth’s symbolic spatial components.La Capacocha del cerro El Plomo tuvo lugar en la cima del apu ubicado en el valle del Mapocho, actual Santiago de Chile. Al respecto, se sostiene que tan importante ritual incaico no solo significó una ceremonia de carácter político-religioso dentro de los valles conquistados, sino, además, un mecanismo de eficacia simbólica como medio de introducción ideológica o andinización de las etnias locales existentes en el valle. Por ello, la utilización de estatuillas antropomorfas dentro del ritual, como la encontrada en 1954 bajo el contexto de huaqueo del sitio arqueológico, pone en evidencia la estandarización de la materialidad simbólica dentro del Incario, pero también distintiva identitariamente hablando, debido al diseño estético del textil. Debido a esta premisa, se cree importante el análisis semiótico bajo un acercamiento desde el mito fundante inca como estrategia política y social de orden, pero también simbólica respecto del espacio