5,001 research outputs found
Paramagnetic Materials and Practical Algorithmic Cooling for NMR Quantum Computing
Algorithmic Cooling is a method that uses novel data compression techniques
and simplecquantum computing devices to improve NMR spectroscopy, and to offer
scalable NMR quantum computers. The algorithm recursively employs two steps. A
reversible entropy compression of the computation quantum-bits (qubits) of the
system and an irreversible heat transfer from the system to the environment
through a set of reset qubits that reach thermal relaxation rapidly.
Is it possible to experimentally demonstrate algorithmic cooling using
existing technology? To allow experimental algorithmic cooling, the
thermalization time of the reset qubits must be much shorter than the
thermalization time of the computation qubits. However such
thermalization-times ratios have yet to be reported.
We investigate here the effect of a paramagnetic salt on the
thermalization-times ratio of computation qubits (carbons) and a reset qubit
(hydrogen). We show that the thermalization-times ratio is improved by
approximately three-fold. Based on this result, an experimental demonstration
of algorithmic cooling by thermalization and magnetic ions is currently
performed by our group and collaborators.Comment: 5 pages, A conference version of this paper appeared in SPIE, volume
5105, pages 185-194 (2003
The Learning of the subject Biology in a Master in Biomedical Physics
BIOLOGY is a dynamic and fascinating science. The study of this subject is an amazing trip for all the students that have a first contact with this subject. Here, we present the development of the study and learning experience of this subject belonging to an area of knowledge that is different to the training curriculum of students who have studied Physics during their degree period. We have taken a real example, the “Elements of Biology” subject, which is taught as part of the Official Biomedical Physics Master, at the Physics Faculty, of the Complutense University of Madrid, since the course 2006/07. Its main objective is to give to the student an understanding how the Physics can have numerous applications in the Biomedical Sciences area, giving the basic training to develop a professional, academic or research career. The results obtained when we use new virtual tools combined with the classical learning show that there is a clear increase in the number of persons that take and pass the final exam. On the other hand, this new learning strategy is well received by the students and this is translated to a higher participation and a decrease of the giving the subject u
Generating functions and multiplicity formulas: the case of rank two simple Lie algebras
A procedure is described that makes use of the generating function of
characters to obtain a new generating function giving the multiplicities of
each weight in all the representations of a simple Lie algebra. The way to
extract from explicit multiplicity formulas for particular weights is
explained and the results corresponding to rank two simple Lie algebras shown
Algorithmic Cooling of Spins: A Practicable Method for Increasing Polarization
An efficient technique to generate ensembles of spins that are highly
polarized by external magnetic fields is the Holy Grail in Nuclear Magnetic
Resonance (NMR) spectroscopy. Since spin-half nuclei have steady-state
polarization biases that increase inversely with temperature, spins exhibiting
high polarization biases are considered cool, even when their environment is
warm. Existing spin-cooling techniques are highly limited in their efficiency
and usefulness. Algorithmic cooling is a promising new spin-cooling approach
that employs data compression methods in open systems. It reduces the entropy
of spins on long molecules to a point far beyond Shannon's bound on reversible
entropy manipulations (an information-theoretic version of the 2nd Law of
Thermodynamics), thus increasing their polarization. Here we present an
efficient and experimentally feasible algorithmic cooling technique that cools
spins to very low temperatures even on short molecules. This practicable
algorithmic cooling could lead to breakthroughs in high-sensitivity NMR
spectroscopy in the near future, and to the development of scalable NMR quantum
computers in the far future. Moreover, while the cooling algorithm itself is
classical, it uses quantum gates in its implementation, thus representing the
first short-term application of quantum computing devices.Comment: 24 pages (with annexes), 3 figures (PS). This version contains no
major content changes: fixed bibliography & figures, modified
acknowledgement
Characterisation of the mechanical and thermal degradation behaviour of natural fibres for lightweight automotive applications
It is well established that light-weighting of automotive parts leads to reduced carbon emissions over vehicle lifetime. Mineral fibres and fillers have a relatively high density and may require high levels of energy in their production, resulting in a large carbon footprint. Natural fibres have been identified as a potential candidate to substitute mineral fillers in automotive application of thermoplastic matrix composites. This paper focuses on the characterisation of the mechanical and thermal degradation of two types of natural fibres (date palm and coir fibres) as part of an evaluation of their potential for the substitution of high density mineral fillers with more environmentally friendly lower density natural fibre reinforcements
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