6,430 research outputs found
Computational Evolutionary Embryogeny
Evolutionary and developmental processes are used to evolve the configurations of 3-D structures in silico to achieve desired performances. Natural systems utilize the combination of both evolution and development processes to produce remarkable performance and diversity. However, this approach has not yet been applied extensively to the design of continuous 3-D load-supporting structures. Beginning with a single artificial cell containing information analogous to a DNA sequence, a structure is grown according to the rules encoded in the sequence. Each artificial cell in the structure contains the same sequence of growth and development rules, and each artificial cell is an element in a finite element mesh representing the structure of the mature individual. Rule sequences are evolved over many generations through selection and survival of individuals in a population. Modularity and symmetry are visible in nearly every natural and engineered structure. An understanding of the evolution and expression of symmetry and modularity is emerging from recent biological research. Initial evidence of these attributes is present in the phenotypes that are developed from the artificial evolution, although neither characteristic is imposed nor selected-for directly. The computational evolutionary development approach presented here shows promise for synthesizing novel configurations of high-performance systems. The approach may advance the system design to a new paradigm, where current design strategies have difficulty producing useful solutions
Generalizations of Tucker-Fan-Shashkin lemmas
Tucker and Ky Fan's lemma are combinatorial analogs of the Borsuk-Ulam
theorem (BUT). In 1996, Yu. A. Shashkin proved a version of Fan's lemma, which
is a combinatorial analog of the odd mapping theorem (OMT). We consider
generalizations of these lemmas for BUT-manifolds, i.e. for manifolds that
satisfy BUT. Proofs rely on a generalization of the OMT and on a lemma about
the doubling of manifolds with boundaries that are BUT-manifolds.Comment: 10 pages, 2 figure
Unconditional Security of Single-Photon Differential Phase Shift Quantum Key Distribution
In this Letter, we prove the unconditional security of single-photon
differential phase shift quantum key distribution (DPS-QKD) protocol, based on
the conversion to an equivalent entanglement-based protocol. We estimate the
upper bound of the phase error rate from the bit error rate, and show that
DPS-QKD can generate unconditionally secure key when the bit error rate is not
greater than 4.12%. This proof is the first step to the unconditional security
proof of coherent state DPS-QKD.Comment: 5 pages, 2 figures; shorten the length, improve clarity, and correct
typos; accepted for publication in Physical Review Letter
On the maximal spectral type of nilsystems
Let be an ergodic -step nilsystem for . We adapt
an argument of Parry to show that decomposes as a sum of a
subspace with discrete spectrum and a subspace of Lebesgue spectrum with
infinite multiplicity. In particular, we generalize a result previously
established by Host, Kra and Maass for -step nilsystems and a result by
Stepin for nilsystems with connected, simply connected .Comment: 12 page
Engineering by fundamental elements of evolution
The method presented in this note mimics two fundamental mechanisms from nature, growth, and development, for the synthesis of new three-dimensional structures. The structures were synthesized to support a load generated by a wind. Every structure grows from a single artificial cell following a set of genes, encoded in an artificial genome shared by all cells. Genes are a set of commands that control the growth process. Genes are regulated by interaction with the environment. The environment is both external and internal to the structure. The performance each structure is measured by its ability to hold the load and other additional engineering criteria. A population of structures is evolved using a genetic algorithm, which alters the genome of two mating individuals. We will present evolved phenotypes with high degrees of modularity and symmetry which evolved according to engineering criteria. Neither one of these two characteristics has been directly imposed as the fitness evaluation, but rather spontaneously emerge as a consequence of natural selection. We will argue that the types of rules we are using in this model are not biased toward any of these characteristics, but rather basic rules for growth and development
Unconditionally Secure Bit Commitment
We describe a new classical bit commitment protocol based on cryptographic
constraints imposed by special relativity. The protocol is unconditionally
secure against classical or quantum attacks. It evades the no-go results of
Mayers, Lo and Chau by requiring from Alice a sequence of communications,
including a post-revelation verification, each of which is guaranteed to be
independent of its predecessor.Comment: Typos corrected. Reference details added. To appear in Phys. Rev.
Let
Noisy Preprocessing and the Distillation of Private States
We provide a simple security proof for prepare & measure quantum key
distribution protocols employing noisy processing and one-way postprocessing of
the key. This is achieved by showing that the security of such a protocol is
equivalent to that of an associated key distribution protocol in which, instead
of the usual maximally-entangled states, a more general {\em private state} is
distilled. Besides a more general target state, the usual entanglement
distillation tools are employed (in particular, Calderbank-Shor-Steane
(CSS)-like codes), with the crucial difference that noisy processing allows
some phase errors to be left uncorrected without compromising the privacy of
the key.Comment: 4 pages, to appear in Physical Review Letters. Extensively rewritten,
with a more detailed discussion of coherent --> iid reductio
A simple proof of the unconditional security of quantum key distribution
Quantum key distribution is the most well-known application of quantum
cryptography. Previous proposed proofs of security of quantum key distribution
contain various technical subtleties. Here, a conceptually simpler proof of
security of quantum key distribution is presented. The new insight is the
invariance of the error rate of a teleportation channel: We show that the error
rate of a teleportation channel is independent of the signals being
transmitted. This is because the non-trivial error patterns are permuted under
teleportation. This new insight is combined with the recently proposed quantum
to classical reduction theorem. Our result shows that assuming that Alice and
Bob have fault-tolerant quantum computers, quantum key distribution can be made
unconditionally secure over arbitrarily long distances even against the most
general type of eavesdropping attacks and in the presence of all types of
noises.Comment: 13 pages, extended abstract. Comments will be appreciate
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