9,756 research outputs found
Faster Base64 Encoding and Decoding Using AVX2 Instructions
Web developers use base64 formats to include images, fonts, sounds and other
resources directly inside HTML, JavaScript, JSON and XML files. We estimate
that billions of base64 messages are decoded every day. We are motivated to
improve the efficiency of base64 encoding and decoding. Compared to
state-of-the-art implementations, we multiply the speeds of both the encoding
(~10x) and the decoding (~7x). We achieve these good results by using the
single-instruction-multiple-data (SIMD) instructions available on recent Intel
processors (AVX2). Our accelerated software abides by the specification and
reports errors when encountering characters outside of the base64 set. It is
available online as free software under a liberal license.Comment: software at https://github.com/lemire/fastbase6
Quantum Entanglement and Communication Complexity
We consider a variation of the multi-party communication complexity scenario
where the parties are supplied with an extra resource: particles in an
entangled quantum state. We show that, although a prior quantum entanglement
cannot be used to simulate a communication channel, it can reduce the
communication complexity of functions in some cases. Specifically, we show
that, for a particular function among three parties (each of which possesses
part of the function's input), a prior quantum entanglement enables them to
learn the value of the function with only three bits of communication occurring
among the parties, whereas, without quantum entanglement, four bits of
communication are necessary. We also show that, for a particular two-party
probabilistic communication complexity problem, quantum entanglement results in
less communication than is required with only classical random correlations
(instead of quantum entanglement). These results are a noteworthy contrast to
the well-known fact that quantum entanglement cannot be used to actually
simulate communication among remote parties.Comment: 10 pages, latex, no figure
Complexes of mercury(II) and zinc(II) with primary aromatic amines
A series of amine complexes has been prepared by reaction of zinc chloride and mercuric chloride with primary aromatic amines. A detailed assignment of the bands in the infra-red spectra of the complexes in the range 4000-625 cm [superscript]-1 is presented. The symmetric and asymmetric N-H stretching frequencies follow the relationship v(sym) = 345.5+ 0.876v(asym). The C-N stretching frequencies exhibit a linear relationship with the Hammett α-functions for the m- and p-substituted amines
Probing spacetime foam with extragalactic sources
Due to quantum fluctuations, spacetime is probably ``foamy'' on very small
scales. We propose to detect this texture of spacetime foam by looking for
core-halo structures in the images of distant quasars. We find that the Very
Large Telescope interferometer will be on the verge of being able to probe the
fabric of spacetime when it reaches its design performance. Our method also
allows us to use spacetime foam physics and physics of computation to infer the
existence of dark energy/matter, independent of the evidence from recent
cosmological observations.Comment: LaTeX, 11 pages, 1 figure; version submitted to PRL; several
references added; very useful comments and suggestions by Eric Perlman
incorporate
Bipartite entangled stabilizer mutually unbiased bases as maximum cliques of Cayley graphs
We examine the existence and structure of particular sets of mutually
unbiased bases (MUBs) in bipartite qudit systems. In contrast to well-known
power-of-prime MUB constructions, we restrict ourselves to using maximally
entangled stabilizer states as MUB vectors. Consequently, these bipartite
entangled stabilizer MUBs (BES MUBs) provide no local information, but are
sufficient and minimal for decomposing a wide variety of interesting operators
including (mixtures of) Jamiolkowski states, entanglement witnesses and more.
The problem of finding such BES MUBs can be mapped, in a natural way, to that
of finding maximum cliques in a family of Cayley graphs. Some relationships
with known power-of-prime MUB constructions are discussed, and observables for
BES MUBs are given explicitly in terms of Pauli operators.Comment: 8 pages, 1 figur
Single-electron tunneling in InP nanowires
We report on the fabrication and electrical characterization of field-effect
devices based on wire-shaped InP crystals grown from Au catalyst particles by a
vapor-liquid-solid process. Our InP wires are n-type doped with diameters in
the 40-55 nm range and lengths of several microns. After being deposited on an
oxidized Si substrate, wires are contacted individually via e-beam fabricated
Ti/Al electrodes. We obtain contact resistances as low as ~10 kOhm, with minor
temperature dependence. The distance between the electrodes varies between 0.2
and 2 micron. The electron density in the wires is changed with a back gate.
Low-temperature transport measurements show Coulomb-blockade behavior with
single-electron charging energies of ~1 meV. We also demonstrate energy
quantization resulting from the confinement in the wire.Comment: 4 pages, 3 figure
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