Ultimate Speed Research Articles

The ultimate speed of magnetic switching in granular recording media.

In magnetic memory devices, logical bits are recorded by selectively setting the magnetization vector of individual magnetic domains either 'up' or 'down'. In such devices, the fastest and most efficient recording method involves precessional switching: when a magnetic field B(p) is applied as a write pulse over a period tau, the magnetization vector precesses about the field until B(p)tau reaches the threshold value at which switching occurs. Increasing the amplitude of the write pulse B(p) might therefore substantially shorten the required switching time tau and allow for faster magnetic recording. Here we use very short pulses of a very high magnetic field to show that under these extreme conditions, precessional switching in magnetic media supporting high bit densities no longer takes place at well-defined field strengths; instead, switching occurs randomly within a wide range of magnetic fields. We attribute this behaviour to a momentary collapse of the ferromagnetic order of the spins under the load of the short and high-field pulse, thus establishing an ultimate limit to the speed of deterministic switching and magnetic recording.

Polymer colloids in photonic materials

Exciting materials known as photonic band-gap materials have come upon the materials science scene and are being studied by many research groups around the world. These new materials operate on light in a way very analogous to the way semiconductors operate on electrons to produce very fast electronic switching and computing circuits. It is imagined that the successful fabrication of these materials will lead to computing machines operating on light and yielding the ultimate speeds in information processing, as electrons typically move only at about one tenth to one half the speed of light. Such devices will require much less heat dissipation and may lead to further miniaturization of computing circuits. New applications in diverse chemical and biochemical sensing are also emerging from these photonic materials. Separation and filtration materials and diverse mesoporous materials and composites are also being developed that rely on such photonic arrays and assemblies as fabrication templates. Polymer colloids in the size range of tens of nm to tens of microns are key components in such new materials and processes. A major limitation in the production of such new materials and devices is that fabrication of such arrays and assemblies is extremely slow and unsuitable for practical manufacturing. Crystallization of charged colloidal suspensions, annealing of core–shell particle arrays, epitaxial growth of crystals from two–dimensional templates, and annealing of thermoreversible gel particle arrays are being explored to ameliorate these limitations. To cite this article: J. Texter, C. R. Chimie 6 (2003).

Quantum limits to dynamical evolution

We establish the minimum time it takes for an initial state of mean energy E and energy spread DE to move from its initial configuration by a predetermined amount. Distances in Hilbert space are estimated by the fidelity between the initial and final state. In this context, we also show that entanglement is necessary to achieve the ultimate evolution speed when the energy resources are distributed among all subsystems.

Folding at the speed limit.

Many small proteins seem to fold by a simple process explicable by conventional chemical kinetics and transition-state theory. This assumes an instant equilibrium between reactants and a high-energy activated state. In reality, equilibration occurs on timescales dependent on the molecules involved, below which such analyses break down. The molecular timescale, normally too short to be seen in experiments, can be of a significant length for proteins. To probe it directly, we studied very rapidly folding mutants of the five-helix bundle protein lambda(6-85), whose activated state is significantly populated during folding. A time-dependent rate coefficient below 2 micro s signals the onset of the molecular timescale, and hence the ultimate speed limit for folding. A simple model shows that the molecular timescale represents the natural pre-factor for transition state models of folding.

SEPARATIONS IN A FLASH

CAPILLARY ELECTROPHOResis (CE) technique devised to explore the ultimate speed limits of chemical separations has come closer to reaching those limits than ever before. The technique greatly improv...

CCD vertex detector for the future linear collider

The R&D program at the LCFI collaboration is dedicated to the building of CCD-based vertex detector, satisfying the challenging requirements of the proposed future linear colliders. The mechanical part of the program targets the development of precision thin detector ladders, using large back-thinned unsupported CCDs under tension. Another part of the program aims to achieve very fast readout of the sensors using column-parallel CCDs, bump bonded to a dedicated CMOS readout chip. Each column of the CCD is read and processed independently, which gives the ultimate speed performance. Some results on modelling of the proposed column parallel CCD with device simulator CAD tools are presented. Tests on fast commercial CCD are being carried out to provide information on noise performance and handling of MIP-like charges at high clock frequencies.

Femtosecond laser pulse induced magnetization reversal: Towards thermo-magnetic writing at THz rates

Abstract- The ultimate speed limit of thermo-magnetic writing is investigated by time-resolved measurements of femtosecond laser pulse induced magnetization reversal in amorphous Gd23.1Fe71.9Co5.0. We prove the resulting reversal dynamics to be governed by the product of two independent processes-the temperature induced changes of the magnetization magnitude times the magnetic field driven reversal of its orientation. Based on this factorization, purely magnetic reversal times are derived from the data. These times show no variation with temperature, but tremendously decrease from several tens of nanoseconds down to only a few picoseconds with increasing excitation density. A minimum reversal time of about 2 ps is found that indicates the possibility of THz thermo-magnetic writing rates. However, the slow cooling of the heated sample limited the maximum achievable writing rates to the GHz range. Only slight improvement of the cooling rates is found when substrates with almost perfect electronic (gold) or phononic (sapphire) heat conductivity are used as heat sinks.

Relativistic quantum protocols: Bit commitment and coin tossing

New relativistic quantum protocols realizing the bit commitment and coin tossing schemes are proposed. The protocols are based on the idea that spatially extended nonstationary orthogonal quantum states inaccessible for measurement cannot be unambiguously distinguished. As the states are transmitted from the region controlled by one party to the region accessible for measurement by the other party, the states become reliably distinguishable when accessed as a whole. Essential points of the protocol are both the quantum character of states and the existence of an ultimate signal propagation speed dictated by special relativity.

A Sampling Approach to Ultra-fast Object Location

This paper examines how sampling can form the basis for ultra-fast location of objects in digital images. The body-based sampling approach that is adopted is unusual in that detection speed is improved for larger objects. The fact of sampling leads initially to more imprecise object location; this poses the problem of finding methods by which object location can be refined without prejudicing the speed of the initial rapid search. In the case of circular objects this problem is straightforward to solve: it is more taxing in the case of ellipses, but a highly effective procedure has been found in the “triple bisection” algorithm, which is simply applied by the bisection of chords across the elliptical objects. These techniques have been applied successfully to the location of cereal grains, which can be modelled as ellipses with a 2:1 aspect ratio. However, the main purpose of this paper is to show that ultra-fast object location is possible with off-camera images, and to indicate the ultimate speeds that are attainable by these means.

Experimental aspects of DNA neural network computation

Adleman showed that hybridization of pairs of complementary DNA strands could be used for molecular computation. We have explored the possibility that a neural network in which the usual axons and neurons are replaced by the diffusion and molecular recognition of DNA is a possible route to fault-tolerant molecular computation. In this paper we review our model for a DNA analog neural network, estimate the ultimate speed of DNA computations, present an enzymatic representation of DNA matrix algebra and show some exploratory experimental results. We discuss the basis for our optimism on the prospects for practical DNA computing.

Promising CMOS ICs Based on Si/CaF2/Si Epitaxial Layers

It is shown that MBE-grown Si/CaF2/Si heterostructures are promising for SOI technology. On the basis of these heterostructures, test MIS/SOI structures were created. The mean electron mobility in the top silicon layer was found to be 450–600 cm2/ (V s). A test CMOS IC with a CoSi2gate and a CaF2gate dielectric was produced. The room-temperature ultimate speed of this structure was estimated (and measured) at a level of 1.5–2 GHz for a supply voltage of 3.0 V.

Going over c

Philip Ball explains why the foundations of physics are not quaking at suggestions that the ultimate speed limit n the speed of light n might have been broken. .

An analysis of technology trends within the electronics industry

This paper begins with a brief review of previous work in the field of technology forecasting and discusses the Fisher Pry model in particular, before concluding with an attempt at forecasting the rate of development of smart technology. The Fisher Pry model is shown to fit well with an assumed ultimate microprocessor clock speed of 1.2GHz. By combining data from multiple sources support is found for the hypothesis that rates of development can be correlated with development activity, as measured by the number of US patents filed in specific technology areas. A forecast for the development of “smart” technology is made to demonstrate how the models may be used to generate forecasts of future developments, where limited data are available.

Estimation of limit strains in disk-type flywheels made of a compliant elastomeric matrix composite undergoing radial creep

Fiber reinforced elastomeric matrix composites (EMCs) offer several potential advantages for construction of rotors for flywheel energy storage systems. One potential advantage, for safety considerations, is the existence of maximum stresses near the outside radius of thick circumferentially wound EMC disks, which could lead to a desirable self-arresting failure mode at ultimate speeds. Certain unidirectionally reinforced EMCs, however, have been noted to creep readily under the influence of stress transverse to the fibers. In this paper, stress redistribution in a spinning thick disk made of a circumferentially filament wound EMC material on a small rigid hub has been analyzed with the assumption of total radial stress relaxation due to radial creep. It is shown that, following complete relaxation, the circumferential strains and stresses are maximized at the outside radius of the disk. Importantly, the radial tensile strains are three times greater than the circumferential strains at any given radius. Therefore, a unidirectional EMC material system that can safely endure transverse tensile creep strains of at least three times the elastic longitudinal strain capacity of the same material is likely to maintain the theoretically safe failure mode despite complete radial stress relaxation.

Optical parallel database management system for page oriented holographic memeories

Current data recall rates from page oriented holographic memories far exceed the ability of electronics toeven read or transmit the data. For database management, we must not only read those data but also query them-computationally, a far more complex task. That task is very severe for electronics. We show here the rudiments of an optical system that can do most of the query operations in parallel in optics, leaving the burden for electronics significantly less. Even here, electronics is the ultimate speed limiter. Nevertheless, we can query data far faster in our optical/electronic system than any purely electronic system.

Observations and models of technology trends within the electronics industry

The paper begins with a brief review of previous work in the field of technology forecasting and discusses the Fisher-Pry model in particular, before concluding with an attempt at producing a forecast of the rate of development of smart technology. The Fisher-Pry model is shown to fit well with an assumed ultimate microprocessor clock speed of 1-2 GHz. By combining data from multiple sources, support is found for the hypothesis that rates of development can be correlated with development activity, as measured by the number of US patents filed in specific technology areas. A forecast for the development of `smart' technology is made to demonstrate how the models may be used to generate forecasts of future developments where limited data is available.

Chord bisection strategy for fast ellipse location

It is shown that a previously proposed rapid sampling technique can be extended using a strategy based on chord bisection. The strategy is characterised by very high speed of operation coupled with accurate location, and can be matched to the level of robustness required by the application. The new technique has been tested on images in which the ellipses are cereal grains with close to 2:1 aspect ratio, but it appears to be suitable for locating ellipses of any eccentricity with near ultimate speed of processing.

Ultrashort light pulses: life in the fast lane

Perhaps the most defining characteristic of modern society is its ever-increasing pace. New technological capabilities, such as computing and telecommunications, are making people more efficient. While these advances increase our standard of living, they also place new demands on our lives and make it all the more important that we maintain the pace of technological change. Of course, we sometimes wonder whether this rate of change will slow down. More specifically, what is the ultimate speed limit in our world? At what point will our computers and communications devices reach fundamental physical limits? And how close is our technology to reaching this ultimate speed limit?

The Interaction Between Classical Physics and Quantum Mechanics on the Experiments of Mass Variation and Ultimate Speed

The Interaction Between Classical Physics and Quantum Mechanics on the Experiments of Mass Variation and Ultimate Speed

A neural online triggering system based on parallel processing

The study of a prototype of the second-level triggering system for operation at LHC conditions is addressed by means of a parallel machine implementation. The 16 node transputer based machine uses a fast digital signal processor acting as a coprocessor for optimizing signal processing applications. A C-language development environment is used for running all applications at ultimate speed. The implementation is based on information supplied by four detectors and includes two phases of system operation: feature extraction and global decision. Feature extraction for calorimeters and global decision processing are performed by means of neural networks. Preprocessing and neural network parameters rest in memory and the activation function is implemented using a look up table. Simulated data for the second-level trigger operation are used for performance evaluation.