Experimental demonstration of four-party quantum secret sharing

Secret sharing is a multiparty cryptographic task in which some secret information is splitted into several pieces which are distributed among the participants such that only an authorized set of participants can reconstruct the original secret. Similar to quantum key distribution, in quantum secret sharing, the secrecy of the shared information relies not on computational assumptions, but on laws of quantum physics. Here, we present an experimental demonstration of four-party quantum secret sharing via the resource of four-photon entanglement

Rapid Bursts of \u3ci\u3eAndrogen-Binding Protein (Abp)\u3c/i\u3e Gene Duplication Occurred Independently in Diverse Mammals

Background The draft mouse (Mus musculus) genome sequence revealed an unexpected proliferation of gene duplicates encoding a family of secretoglobin proteins including the androgen-binding protein (ABP) α, β and γ subunits. Further investigation of 14 α-like (Abpa) and 13 β- or γ-like (Abpbg) undisrupted gene sequences revealed a rich diversity of developmental stage-, sex- and tissue-specific expression. Despite these studies, our understanding of the evolution of this gene family remains incomplete. Questions arise from imperfections in the initial mouse genome assembly and a dearth of information about the gene family structure in other rodents and mammals. Results Here, we interrogate the latest \u27finished\u27 mouse (Mus musculus) genome sequence assembly to show that the Abp gene repertoire is, in fact, twice as large as reported previously, with 30 Abpa and 34 Abpbg genes and pseudogenes. All of these have arisen since the last common ancestor with rat (Rattus norvegicus). We then demonstrate, by sequencing homologs from species within the Mus genus, that this burst of gene duplication occurred very recently, within the past seven million years. Finally, we survey Abp orthologs in genomes from across the mammalian clade and show that bursts of Abp gene duplications are not specific to the murid rodents; they also occurred recently in the lagomorph (rabbit, Oryctolagus cuniculus) and ruminant (cattle, Bos taurus) lineages, although not in other mammalian taxa. Conclusion We conclude that Abp genes have undergone repeated bursts of gene duplication and adaptive sequence diversification driven by these genes\u27 participation in chemosensation and/or sexual identification

Anisotropic diffusion in continuum relaxation of stepped crystal surfaces

We study the continuum limit in 2+1 dimensions of nanoscale anisotropic diffusion processes on crystal surfaces relaxing to become flat below roughening. Our main result is a continuum law for the surface flux in terms of a new continuum-scale tensor mobility. The starting point is the Burton, Cabrera and Frank (BCF) theory, which offers a discrete scheme for atomic steps whose motion drives surface evolution. Our derivation is based on the separation of local space variables into fast and slow. The model includes: (i) anisotropic diffusion of adsorbed atoms (adatoms) on terraces separating steps; (ii) diffusion of atoms along step edges; and (iii) attachment-detachment of atoms at step edges. We derive a parabolic fourth-order, fully nonlinear partial differential equation (PDE) for the continuum surface height profile. An ingredient of this PDE is the surface mobility for the adatom flux, which is a nontrivial extension of the tensor mobility for isotropic terrace diffusion derived previously by Margetis and Kohn. Approximate, separable solutions of the PDE are discussed.Comment: 14 pages, 1 figur

The Impact of Foreign Postings on Accompanying Military Spouses: An Ethnographic Study.

As part of an ethnographic study, the impact of foreign postings on spouses who accompany military personnel was explored. Individual interviews and focus groups with 34 British military spouses based in one location in southern Europe were conducted. Key findings suggested that reaction to a foreign posting was a reflection of personal attitudes, prior experiences, support, ability to adjust to change and strength of relationship with the serving spouse and community. For many the experience was positive due to the increased opportunity for family time, for others this helped to compensate for the difficulties experienced. Some military spouses experienced significant distress on the posting, particularly if the family was not well-supported. The potential implications of military spouses not adapting to foreign postings have significant implications for healthcare practice. Provision of more appropriate support resources before and during the posting would facilitate the transition for the military spouse and their family

Controlled Quantum Secret Sharing

We present a new protocol in which a secret multiqubit quantum state $\ket{\Psi}$ is shared by $n$ players and $m$ controllers, where $\ket{\Psi}$ is the encoding state of a quantum secret sharing scheme. The players may be considered as field agents responsible for carrying out a task, using the secret information encrypted in $\ket{\Psi}$, while the controllers are superiors who decide if and when the task should be carried out and who to do it. Our protocol only requires ancillary Bell states and Bell-basis measurements.Comment: 6 pages, 0 figure, RevTeX4; published version with minor change

Some Directions beyond Traditional Quantum Secret Sharing

We investigate two directions beyond the traditional quantum secret sharing (QSS). First, a restriction on QSS that comes from the no-cloning theorem is that any pair of authorized sets in an access structure should overlap. From the viewpoint of application, this places an unnatural constraint on secret sharing. We present a generalization, called assisted QSS (AQSS), where access structures without pairwise overlap of authorized sets is permissible, provided some shares are withheld by the share dealer. We show that no more than $\lambda-1$ withheld shares are required, where $\lambda$ is the minimum number of {\em partially linked classes} among the authorized sets for the QSS. Our result means that such applications of QSS need not be thwarted by the no-cloning theorem. Secondly, we point out a way of combining the features of QSS and quantum key distribution (QKD) for applications where a classical information is shared by quantum means. We observe that in such case, it is often possible to reduce the security proof of QSS to that of QKD.Comment: To appear in Physica Scripta, 7 pages, 1 figure, subsumes arXiv:quant-ph/040720

How to share a quantum secret

We investigate the concept of quantum secret sharing. In a ((k,n)) threshold scheme, a secret quantum state is divided into n shares such that any k of those shares can be used to reconstruct the secret, but any set of k-1 or fewer shares contains absolutely no information about the secret. We show that the only constraint on the existence of threshold schemes comes from the quantum "no-cloning theorem", which requires that n < 2k, and, in all such cases, we give an efficient construction of a ((k,n)) threshold scheme. We also explore similarities and differences between quantum secret sharing schemes and quantum error-correcting codes. One remarkable difference is that, while most existing quantum codes encode pure states as pure states, quantum secret sharing schemes must use mixed states in some cases. For example, if k <= n < 2k-1 then any ((k,n)) threshold scheme must distribute information that is globally in a mixed state.Comment: 5 pages, REVTeX, submitted to PR

Discovery of Stable and Selective Antibody Mimetics from Combinatorial Libraries of Polyvalent, Loop-Functionalized Peptoid Nanosheets.

The ability of antibodies to bind a wide variety of analytes with high specificity and high affinity makes them ideal candidates for therapeutic and diagnostic applications. However, the poor stability and high production cost of antibodies have prompted exploration of a variety of synthetic materials capable of specific molecular recognition. Unfortunately, it remains a fundamental challenge to create a chemically diverse population of protein-like, folded synthetic nanostructures with defined molecular conformations in water. Here we report the synthesis and screening of combinatorial libraries of sequence-defined peptoid polymers engineered to fold into ordered, supramolecular nanosheets displaying a high spatial density of diverse, conformationally constrained peptoid loops on their surface. These polyvalent, loop-functionalized nanosheets were screened using a homogeneous Förster resonance energy transfer (FRET) assay for binding to a variety of protein targets. Peptoid sequences were identified that bound to the heptameric protein, anthrax protective antigen, with high avidity and selectivity. These nanosheets were shown to be resistant to proteolytic degradation, and the binding was shown to be dependent on the loop display density. This work demonstrates that key aspects of antibody structure and function-the creation of multivalent, combinatorial chemical diversity within a well-defined folded structure-can be realized with completely synthetic materials. This approach enables the rapid discovery of biomimetic affinity reagents that combine the durability of synthetic materials with the specificity of biomolecular materials