16,682 research outputs found
Study of 'ratio' automatically assembled structures final report, 15 jun. 1963 - 15 jun. 1964
Structural analysis of RATIO automatically assembled panel sections for application to spaceborne paraboloidal antenn
Topological Protection and Quantum Noiseless Subsystems
Encoding and manipulation of quantum information by means of topological
degrees of freedom provides a promising way to achieve natural fault-tolerance
that is built-in at the physical level. We show that this topological approach
to quantum information processing is a particular instance of the notion of
computation in a noiseless quantum subsystem. The latter then provide the most
general conceptual framework for stabilizing quantum information and for
preserving quantum coherence in topological and geometric systems.Comment: 4 Pages LaTeX. Published versio
FilosofĂa y medicina en la antigua Grecia: modelos de conocimiento y sus repercusiones
This paper investigates some of the complexities in the relationship between philosophy and medicine in ancient Greece. Some philosophers cite medicine as an analogue to philosophy, for instance in connection with the claim that there can be objective experts to whom mere lay people should defer. Some doctors, however, object to what they represent as the dogmatic, 'a priori', strands of philosophical inquiry and develop an alternative, empiricist, epistemology and methodology. Recollection and experience are invoked in strikingly divergent ways as the debate within and between different philosophical and medical traditions developed.En este trabajo se investigan algunas de las complejidades de la relación entre la filosofía y la medicina en la antigua Grecia. Algunos filósofos citan la medicina como análoga de la filosofía, por ejemplo en conexión con la afirmación de que puede haber expertos objetivos a quienes los meros profanos deben someterse. Algunos médicos, sin embargo, ponen objeciones a lo que representan como líneas dogmáticas, apriorísticas, de la indagación filosófica, y desarrollan una epistemología y una metodología alternativas de carácter empírico. El recuerdo y la experiencia se invocan de formas llamativamente divergentes porque el debate se desarrollaba dentro de y entre diferentes tradiciones filosóficas y médicas
A Discrete Four Stroke Quantum Heat Engine Exploring the Origin of Friction
The optimal power performance of a first principle quantum heat engine model
shows friction-like phenomena when the internal fluid Hamiltonian does not
commute with the external control field. The model is based on interacting
two-level-systems where the external magnetic field serves as a control
variable.Comment: 4 pages 3 figure
Spintronics and Quantum Dots for Quantum Computing and Quantum Communication
Control over electron-spin states, such as coherent manipulation, filtering
and measurement promises access to new technologies in conventional as well as
in quantum computation and quantum communication. We review our proposal of
using electron spins in quantum confined structures as qubits and discuss the
requirements for implementing a quantum computer. We describe several
realizations of one- and two-qubit gates and of the read-in and read-out tasks.
We discuss recently proposed schemes for using a single quantum dot as
spin-filter and spin-memory device. Considering electronic EPR pairs needed for
quantum communication we show that their spin entanglement can be detected in
mesoscopic transport measurements using metallic as well as superconducting
leads attached to the dots.Comment: Prepared for Fortschritte der Physik special issue, Experimental
Proposals for Quantum Computation. 15 pages, 5 figures; typos corrected,
references adde
Quantum search without entanglement
Entanglement of quantum variables is usually thought to be a prerequisite for
obtaining quantum speed-ups of information processing tasks such as searching
databases. This paper presents methods for quantum search that give a speed-up
over classical methods, but that do not require entanglement. These methods
rely instead on interference to provide a speed-up. Search without entanglement
comes at a cost: although they outperform analogous classical devices, the
quantum devices that perform the search are not universal quantum computers and
require exponentially greater overhead than a quantum computer that operates
using entanglement. Quantum search without entanglement is compared to
classical search using waves.Comment: 9 pages, TeX, submitted to Physical Review Letter
Analog quantum error correction
Quantum error-correction routines are developed for continuous quantum
variables such as position and momentum. The result of such analog quantum
error correction is the construction of composite continuous quantum variables
that are largely immune to the effects of noise and decoherence.Comment: Ten pages, Te
- …