The technologies of Josephson-junction-based qubits have been progressing rapidly, ever since its first demonstration by a superconducting charge qubit1. A variety of systems have been implemented with remarkable progress in coherence time and read-out schemes. Although the current level of this solid-state device is still not as advanced as that of the most advanced microscopic-system-based qubits, these developments, together with the potential scalability, have renewed its position as a strong candidate as a building block for the quantum computer. Recently, coherent oscillation and microwave spectroscopy in capacitively-coupled superconducting qubits have been reported. The next challenging step toward quantum computation is a realization of logic gates. Here we demonstrate a conditional gate operation using a pair of coupled superconducting charge qubits. Using a pulse technique, we prepare different input states and show that they can be transformed by controlled-NOT (C-NOT) gate operation in the amplitude of the states. Although the phase evolution during the gate operation is still to be clarified, the present results are a major step toward the realization of a universal solid-state quantum gate.

Small Josephson junctions are known to be very susceptible to noise. We have utilized this property in developing methods to measure noise as well as environmental resonance modes in mesoscopic systems. We review recent results on tunnel junction systems and show also that higher order moments of shot noise can be addressed with the present method based on the noise-induced modification of incoherent tunneling of Cooper pairs.

Hyperfine coupling of electron spins to nuclear spins is studied for a GaAs-based double quantum dot in the spin blockade. A current flowing through the double dot shows time-dependent oscillations with a period of as long as 200 sec.

We discuss schemes for the realization of quantum information devices using optical techniques and the electronic and spin degrees of freedom of diluted impurities in semiconductors. State-of-the-art nano-optical techniques can address a single impurity localized in a semiconductor. The optical properties of the host can be used to efficiently control the internal degrees of freedom of the impurities, and therefore to encode and process quantum information.

A quantum computer based on the manipulation and detection of coherent states of electrons localized above a helium film is described. Each quantum logic element (qubit) is made of a combination of the ground and first excited states of an electron trapped in the image potential well at the surface. Potentials applied to micro-electrodes located beneath each electron confine the lateral motion of the electron and are used to operate gates. Mechanisms for one- and two-qubit logic operations and a readout of the final state are discussed. The principle decay channel for the excited state is via the emission of one phonon into the bulk liquid. Dechoherence times are calculated to be of order of 100 μs and allow greater than 10⁴ serial operations.

We present simulations of the effects of dephasing on the shot noise properties of mesoscopic coherent devices, such as chaotic cavities and Aharonov-Bohm rings. We adopt a phenomenological model that exploits the statistical nature of the dephasing mechanism and is able to cover the intermediate regime between a fully coherent and completely incoherent (i.e., semiclassical) transport. By investigating conductance and noise properties as a function of the dephasing length, we conclude that decoherence has no specific effect on shot noise which can be distinguished from the one it has on conductance. In addition, when a large number of conducting channels is considered, semiclassical and quantum behavior must converge, yielding as a consequence the independence of DC and noise properties from dephasing.

In the present paper, emphasis is laid on those RTS showing a capture process, which deviates from the standard Shockley-Read-Hall kinetics. A modified two-step approach is proposed. In this case the charge carrier quantum transitions represent a primary process X(t), which involves two or three quantum states. The measurable quantity is the current modulation, which has discrete states, too. The current modulation is then represented by a secondary process Y(t). The proposed model can explain some of the complex switching phenomena being measured in nanoscale devices. The quadratic dependence of the capture rate on the current and the noise spectral density dependence on the current and temperature are analysed. It is shown that the occupation time probability density for emission is given by a superposition of two exponential dependencies, whereas the capture time constant distribution is purely exponential.

Recent discovery of the coherent lasing from various disordered materials adds a new dimension to the conventional physics of light propagation in multiply scattering media. It suggests that in the situation, when the propagation of light is diffusive on average, the coherent feedback can be provided by the sparse disorder configurations that efficiently trap a photon, and thus, serve as random resonators. This scenario of random resonators has been substantiated experimentally by the ensemble averaging of the power Fourier transforms of the random emission spectra. In this paper the current status of the experiment and theory of coherent random lasing is reviewed.

The conceptual foundations of the special and general theories of relativity differ greatly from those of quantum mechanics. Yet in all cases investigated so far, quantum mechanics seems to be consistent with the principles of relativity theory, when interpreted carefully. In this paper I report on a new investigation of this consistency using a model of a quantum clock to measure time intervals; a topic central to all metric theories of gravitation, and to cosmology. Results are presented for two important scenarios related to the foundations of relativity theory: the speed of light as a limiting velocity and the weak equivalence principle (WEP). These topics are investigated in the light of claims of superluminal propagation in quantum tunnelling and possible violations of WEP. Special attention is given to the role of highly non-classical states. I find that by using a definition of time intervals based on a precise model of a quantum clock, ambiguities are avoided and, at least in the scenarios investigated, there is consistency with the theory of relativity, albeit with some subtleties.

We have recently measured pulsed electron spin resonance (ESR) from electrons bound to donors in silicon. Measurements made in the late 1950's showed that these spins were long-lived, but we find coherence times that are about two orders of magnitude longer than previously seen. We have also measured the spin-decoherence of free, 2- dimensional electrons in an ultra-high mobility Si/SiGe quantum well. The coherence time of the 2D electron spins is long in comparison to compound semiconductor systems, but several orders of magnitude shorter than that of the donorbound electrons. Spin-orbit coupling in the form of the Structural Inversion Asymmetry (Rashba effect) appears to be the cause of the increased decoherence rate of the 2D electrons' spin. For architectures employing quantum dots at a heterointerface, the Rashba effect is not expected to cause a loss of spin coherence while the electron is in the ground state, but thermal excitation to upper dot levels could lead to decoherence. We discuss ways in which this Rashba term can be minimized in Si-based structures, as well as other physical systems (electrons on liquid helium, for example) in which much longer spin coherence times can be expected.

We discuss various approaches to create and detect electron spin entanglement, with a special emphasis on the study of the efficiency of a beam splitter as a detector for entangled electron pairs. In particular, we focus on the consequence of considering wavepacket states for the electrons as they enter the beam splitter in order to illustrate their particle characteristics. We then introduce double quantum dot as a possible source of spin entangled electrons. In particular, we show that a double quantum dot turnstile is, in principle, an efficient electron spin entangler or entanglement filter because of the exchange coupling between the dots and the tunable input/output potential barriers.

We discuss non-trivial effects which emerge when a single spin is embedded in various (normal and Josephson) junctions and discuss a new experimental technique to probe single spin dynamics. We show that current may be influenced by the presence of a single spin and the converse. New spin nutations in a Josephson junction are predicted. We discuss a new general exerimental technique to probe single spin dynamics via noise spectroscopy- by carefully monitoring the current noise, important information can be extracted regarding a single spin motion.

In this survey at first the general figures of merit of solid-state sensors as sensitivity, dynamic range and noise equivalent signal are defined. With this the main phenomenological parameters as tangential sensitivity, noise figure, noise temperature, noise resistance is treated, and the usefulness of the tangential sensitivity is emphasized. The difference between the phenomenological parameters and the physical noise is pointed out with examples. Finally the basic noise aspects of some often used classical sensor elements as resistance; Hall-plate and diode are reviewed.

In recent years, MEMS devices have been developed for a wide variety of applications. Many of the signals that these sensors are intended to detect are expressed as forces that stress or deflect the micromechanical structure. As sensors are miniaturized, these forces naturally become smaller, and techniques for detection are required to improve. As the force sensing capabilities of MEMS devices have improved, it has become possible to apply these devices to interesting scientific experiments on biological systems.

Metal oxide gas sensors suffer from lack of selectivity and response drift. The use of sensor dynamics has been introduced to ameliorate sensor performance. The usual approach consists of modulating the operating temperature of gas sensors. Temperature modulation alters the kinetics of the adsorption and reaction processes taking place at sensors' surface. This results in response patterns that are characteristic of gas/sensor pairs. Despite the fact that a great deal of work has been done, the selection of the modulating frequencies remains an obscure and non-systematic method. A new approach to systematically select frequencies is discussed. The method is based on the use of pseudo-random binary sequences (MLS) to modulate the working temperature of gas sensors in a wide frequency range. The impulse response of a pair sensor-gas can be estimated from the circular cross-correlation of the MLS and the sensor response sequences. From the study of the impulse response in the frequency domain, an identification of the modulating frequencies that convey important information to both identify and quantify gases is obtained.

High quality quantum Hall bilayers at total filling factor 1 exhibit a strong zero bias tunneling resonance that is akin to the Josephson effect. Experimentally this resonance has a measurable width even at very low temperatures, indicating the existence of some low energy excitations with no analog in the single layer quantum Hall system. We exploit a simple model of the quantum Hall bilayer in which the relative phase of the electron wavefunctions in the two wells is the only degree of freedom to perform Langevin dynamics simulations of this system. Disorder is explicitly included in the model, which we find induces strings of overturned phase and vortices in the low state. This "string glass" state supports low-energy localized excitations which are typical of glasses, and qualitatively explains many of the existing experimental observations.

We present for the first time a complex network approach to the study of the electrical properties of single protein devices. In particular, we consider an electronic nanobiosensor based on a G-protein coupled receptor. By adopting a coarse grain description, the protein is modeled as a complex network of elementary impedances. The positions of the alpha-carbon atoms of each amino acid are taken as the nodes of the network. The amino acids are assumed to interact electrically among them. Consequently, a link is drawn between any pair of nodes neighboring in space within a given distance and an elementary impedance is associated with each link. The value of this impedance can be related to the physical and chemical properties of the amino acid pair and to their relative distance. Accordingly, the conformational changes of the receptor induced by the capture of the ligand, are translated into a variation of its electrical properties. Stochastic fluctuations in the value of the elementary impedances of the network, which mimic different physical effects, have also been considered. Preliminary results concerning the impedance spectrum of the network and its fluctuations are presented and discussed for different values of the model parameters.

WO₃ nanoparticles were generated by gas deposition. Deposits on Al substrates were studied by scanning force microscopy operated in the intermittent-contact (tapping) mode. At low surface coverage (< 0.5 %), we observed single nanoparticles with a mean size of ~ 1.5 nm. An increase of the amount of particles led to agglomerates, which appeared at surface coverages as low as 2 to 4 %. At full coverage the mean agglomerate size was ~ 5 nm. This value did not change as the sample was annealed at temperatures up to 250 °C. The size distribution of the agglomerates was found to be log-normal, i.e., similar to the size distribution of the gas-phase nanoparticles forming the deposit. For explaining the obtained log-normal size distribution of the agglomerates simulations of the agglomeration process were also carried out.

Nanoparticle films of Pd_xWO₃, with x being 0.01 or 0.12, were made by dual-beam gas deposition. Resistance noise as well as dc resistance were measured during exposure to ethanol and hydrogen gas. For ethanol concentrations exceeding 50 ppm, changes in the resistance noise gave 300 times larger detection sensitivity than changes in the dc resistance. This sensitivity reached a maximum at 250 °C and was very reproducible for ethanol sensing.

A quantum-mechanical many-particle system may exhibit non-local behavior in that measurements performed on one of the particles can affect a second one that is far apart. These so-called entangled states are crucial for the implementation of quantum information protocols and gates for quantum computation. Here, we use ultrafast optical pulses and coherent techniques to create and control spin entangled states in an ensemble of up to three non-interacting electrons bound to donors in a CdTe quantum well. Our method, relying on the exchange interaction between localized excitons and paramagnetic impurities, can in principle be applied to entangle an arbitrarily large number of spins.

A quantum computer has been the focus of considerable attention since it realizes a much higher operating speed than conventional computers. However, there are many important issues regarding algorithms as well as hardware in the realization of a quantum computer. To realize the calculation speed of a quantum computer, several quantum-computing emulators utilizing parallel operation using integrated circuits were fabricated. Consequently, an emulator of 75 quantum bits was realized, and the feasibility of a high-speed quantum-computing emulator using integrated circuits has been proved.

Strong many-particle localization is studied in a 1D array of perpetually coupled qubits and an equivalent 1D system of interacting fermions. We construct a bounded sequence of the on-site fermion energies, or qubit transition frequencies, that suppresses resonant hopping between both nearest and remote neighbors. Besides quasi-exponential decay of the single-particle transition amplitude,it leads to long lived strongly localized many-particle states. This makes quantum computing with time-independent qubit coupling viable.

We analyze localization of interacting excitations in a system of qubits or spins. The system is modeled by a spin chain with an anisotropic (XXZ) exchange coupling in a magnetic field. Localization occurs on a defect with an excess on-site spin-flip energy. Such a defect corresponds to a qubit with the level spacing different from other qubits. Because of the interaction, a single defect may lead to multiple localized states. We find energy spectra and localization lengths of the two-excitation states. An excitation remains localized on the defect even where energy conservation allows scattering into extended states. This is due to destructive quantum interference in the two-excitation scattering channels, and it facilitates the operation of a quantum computer. Analytical results are obtained for strong anisotropy and are confirmed by numerical studies.

We discuss the quantum algorithms simulating complex dynamics on quantum computers in presence of imperfections. The effects of random errors and static imperfections for quantum gates are analyzed. We also study numerically how a sound signal stored in a quantum computer can be recognized and restored with a minimal number of measurements in presence of random quantum gate errors. A method developed uses elements of MP3 sound compression and allows to recover human speech and sound of complex quantum wavefunctions.

We study dynamical properties of systems with many interacting Fermi-particles under the influence of static imperfections. Main attention is payed to the time dependence of the Shannon entropy of wave packets, and to the fidelity of the dynamics. Our question is how the entropy and fidelity are sensitive to the noise. In our study, we use both random matrix models with two-body interaction and dynamical models of a quantum computation. Numerical data are compared with analytical predictions.

In quantum information and quantum computing, the carrier of information is some quantum system and information is encoded in its state. The state, however, is not an observable in quantum mechanics, thus a fundamental problem arises: after processing the information it has to be read out or, in other words, the state of the system must be determined. When the possible target states are orthogonal, this is a relatively simple task, provided the set of possible target states is known. But when the possible target states are not orthogonal their discrimination is far from being trivial even if their set is known. Thus the problem of discriminating among non-orthogonal states is ubiquitous in quantum information and quantum computing, underlying all communication and computing schemes. It is the subject of this talk to review recent theoretical and experimental advances in this field.

Quantum simulations, supported by experiments, show that photomixing in laser-assisted field emission offers promise as a new mechanism for wide-band tunable sources at terahertz frequencies. In this technique the bandwidth is only limited by the methods for coupling power from the current oscillations that are generated in photomixing, and not by the fundamental processes that generate the mixer current. Photomixing is simulated as a stationary stochastic process in which the frequencies and phases of the incident optical radiation are random variables. The waveform of the current is determined by solving the time-independent Schroedinger equation at discrete time steps for which the potential barrier is a superposition of the instantaneous value of the radiation field and the static barrier. These samples satisfy the criteria of a Poisson process to allow for the discrete emission of electrons at the specified total current. The one-sided power spectral density is calculated with the FFT to produce periodogram estimates. The simulations show that the signal-to-noise ratio may be increased by (1) raising the power flux density of each laser, (2) raising the DC static current, (3) reducing the linewidth of each laser, and (4) using a static current densityof no more than 10¹⁰ A/m².

Several studies have demonstrated the suitability of noise added methodology to improve the performances of bistable or quasi-linear devices. As an example, observations of the Stochastic Resonance phenomenon in the Brownian System reveal the possibility to use exogenous noise to improve the behaviour of several sensing devices or to adapt them to perform adequately in the presence of noise. Moreover, in the field of quasi-linear systems the possibility to use dithering to increase the device operating range was addressed. In this paper, an overview of the methodologies aimed to improve the performances of stochastically modulated systems is presented. In particular the possibility to improve the performance of both bistable or quasi-linear measuring systems is shown by using a number of examples that have been developed in a number of years by researchers working at DIEES of the University of Catania (Italy).

Recently a novel signal processing theory related with noise has grown and proven. Certain complex systems can improve performance with added optimal noise that classical theory cannot explain. Their behavior may be represented by a simplified scheme that combines both a deterministic and stochastic source. To that end, we are using noise in remote temperature sensing system to enhance their function without altering the system. A new investigation of noise added scheme has been realized by an embedded heater for CMOS compatible thermoelectric infrared sensor. The design and fabrication of thermopile sensors are realized by using 1.2μm CMOS IC technology combined with a subsequent anisotropic front-side etching. We firstly develop an active thermopile with a heater embedded which is easily and naturally driven by a noise generation circuit. The stochastic resonance theory can be realized as a reduction in threshold of temperature detection. We have shown the possibility of improving the performance of remote temperature sensing system in the presence of noise. The strategy depends on the application. Stochastic resonance can reduce threshold detection resolution and greatly improve the temperature detection limit with a low cost scheme without using higher resolution ADC.

The analysis has shown that high pressure and high temperature piping in fossil and nuclear power plants suffer from unexpected and rarely predictable failures. To guarantee operational safety and to prevent failures authors have performed the complex investigations and have created Quantitative Acoustic Emission NDI technology for revealing, identifying and assessing flaws in equipment operated under strong background noise condition. These enabled: Overall inspection of the piping operated under stress, temperature, pressure, steam flow and loading, variation. Locating suspected zones and zones of flaw development with low J-integral value and the great variation of the dynamic range of flaws danger level. Identification of flaw types and their danger level. Detection of defective components in service prior to shut down. The continuous and the burst Acoustic Emission (AE) were used in combination as an information tool. As result, the significant number of flaws such as creep at stage 3a-3b, closed-edge micro-cracks, systems of randomly dispersed pores and inclusions, plastic deformation development around them, or/and individual micro-cracking were revealed, identified and assessed in 50 operating high energy piping. The findings and assessing flaw danger level obtained by QAE NDI were confirmed by independent NDI methods as TOFD, X-ray, replication, metallurgical investigations, etc. The findings and assessing flaw danger level obtained by QAE NDI were confirmed by independent NDI methods such as TOFD, X-ray, replication, metallurgical investigations, etc

Corrosion in concrete can cause disastrous destructions of bridges and other constructions. Different methods of corrosion monitoring can be applied including electrochemical noise despite its disadvantageous limitations. Noise measurements enable continuous monitoring of corrosive conditions inside concrete and recognition when corrosion starts to make trouble there. Results of electrochemical noise measurements in concrete are presented. Polarization resistance of carbon steel is estimated by current and voltage noise measurements. Changes of factor 2-4 of the estimated polarization resistance are recognized during time of noise registration. The observed changes in uniform corrosion rate can be identified by electrochemical noise analysis. Limitations of the applied method of polarization resistance evaluation are considered and presented.

The resistance fluctuations of sensors can give improved selectivity and sensibility and the analysis is limited to power spectrum density only. Non-Gaussian low frequency noise components can be observed in nanoparticle gas sensors especially if some of the characteristics length scales is in the submicron range. These components can be characterized by higher-order spectra (HOS). In this paper, bispectra and trispectra are used. The modulus and phase characteristics of the higher-order spectra of the observed resistance fluctuations are analyzed separately. The explored sensors consist of WO₃ films, with Pd nanoparticles uniformly distributed in the oxide structure.

Nanoparticle films of crystalline WO₃, designed for gas sensing applications, were deposited on alumina substrates by reactive gas deposition. H₂S, ethanol vapour, and binary mixtures of ethanol/H₂S, ethanol/NO₂ and H₂S/NO₂ were used in different concentrations for testing the performance of the sensor device. The sensor was operated in dynamic mode by modulating its temperature between 150 and 250 °C. Coefficients were extracted by applying Fast Fourier Transform (FFT) and Discrete Wavelet Transform (DWT) methods to the dynamic resistance response of the sensor. These coefficients were then used as inputs for pattern recognition methods to extract both quantitative (concentration) and qualitative (chemical selectivity) information about the test gases. After sensor calibration, it was possible to detect as little as 200 ppb of ethanol and 20 ppb of H2S with good accuracy. Furthermore, ethanol and H₂S could be detected with good sensitivity and selectivity in the presence of both reducing and oxidising gases.

The minor carrier effective lifetime of middle wavelength infrared HgCdTe photoconductive sensors is relatively large. The sweep-out effect may easily emerge in small size sensors which decrease the responsitivity. In order to eliminate this effect, an overlap structure is often used. In this paper the low frequency noise characteristics of HgCdTe sensors with this overlap structure is studied. It is shown that not only the low frequency noise of sensors with this overlap structure is much larger than that of the conventional ones, but also Hooge parameter and frequency exponent are changed with bias current especially for this overlap structure. An edge-contacted asymmetrical metal-insulator-semiconductor model is presented to explain the noise characterization. It is found that a depletion layer would appear from the HgCdTe surface under overlap electrodes when the sensors are biased. Its thickness changed with its position because of the difference of the voltage. When the bias current is increased, this depletion layer is widening. Also Hooge parameter and frequency exponent increased which are similar to the MISFETs. It is shown by experiments that the enhancement of sensor noise for overlap structure is mainly caused by the depletion layer under overlap electrodes.

PbS photoconductors have been fabricated by the chemical deposition method onto glass substrates. The investigated samples prepared from layers deposited 20 years ago. The photoconductivity of free and encapsulated detectors was investigated at room temperature. The performance of PbS detectors was practically not changed after long time storage at laboratory conditions, or easily recovered after vacuum treatment at 75 °C. The low-frequency (10Hz...20 kHz) noise spectra were measured in dark and during infrared exposure. The carrier lifetime was determined by measuring the frequency response of the device. The changes of the resistance during infrared and ultraviolet exposure were measured too. After the UV illumination the magnitude of the noise levels did not changed too much, however the character of the spectra has definitely changed. The spectra became similar to 1/f indicating that the dominance of generation-recombination noise is less pronounced. The persistent conductivity increase, which occurred by the ultraviolet light is interpreted as the hydration of the oxidized surface.

The low frequency noise generated by optoelectronic coupled devices (OCDs) was measured in the system designed and constructed by authors. The investigations were carried out for optoelectronic devices of CNY 17 type. Number of N = 10⁶ noise samples was recorded for statistical analysis for each investigated OCD. The amplitude distributions and cumulative distribution functions were calculated for each samples data records. Statistical properties of low frequency noise of OCDs were established by estimating following parameters: mean value, variance, skewness and kurtosis. The investigated time series have not Gaussion distributions. Stationarity of the four estimated parameters was tested. It was found that the probability density function of noise could be used for the recognition of the Random Telegraph Signal (RTS) noise together with spectrum analysis.

In the paper, we present UV-detection system and it¢s noise model. It consist of GaN photodiode produced by ITME in Warsaw, and low noise preamplifier. The Schotttky barrier MSM and p-π-n visible blind detectors on gallium nitride were used. The main purpose was to analyse the first stage of UV receiver (photodetector plus low noise preamplifier) to optimise them providing maximal value of signal-to-noise ratio.

Process of the origin and relaxation of the fluctuation of distribution function of conduction electrons in space-homogenous and non-degenerate equilibrium semiconductors is discussed. The fluctuations of electron distribution function, formed as result of the internal fluctuations of the phonon system, are studied. The physical mechanisms of the origin and following slow (diffusion) damping of the equilibrium fluctuations of the electron and phonon distribution functions are represented. It is shown that in low frequency region the Fourier-component of distribution function fluctuations of predominantly long wavelength electrons and phonons are depends on frequency by law ω^-1/2.

The influence of surface scatterings on damping of the equilibrium fluctuations of the electron distribution function, originating in the bulk of homogeneous, bounded semiconductors is discussed as a result of random phonon-phonon scatterings. The peculiarities of (acoustic) phonons refraction on the flat interface are investigated. It is shown that only certain discrete magnitudes of phonons wave vectors satisfy the refraction laws. So-called "refraction points" are discovered. It is established that relaxation of longer-wavelength electron distribution function fluctuation depends on processes of surface reflection and refraction of electrons and phonons. It is shown that in the semiconductors with not very large sizes the damping is also conditioned by the phonons quasi-momentum direction diffusion. It the microscopic mechanism of such diffusion is analyzed.

Quantitative Acoustic Emission (QAE) technology, physical and mathematical models were created for the reliable and precise identification and evaluation of the danger level (the J-integral value) of a developing main crack in a system of interacting micro- cracks, and the reliable assessment of the remaining lifetime of low density polyethylene (LDPE) reactor tubes that contain cracks. These innovations made it possible to carry out pioneer investigations and established previously unknown dependences, phenomena and criteria, such as: Interdependence between the J-integral value of the flaw and the remaining lifetime of tubes from steel in design condition that contained system of inclusions, micro- cracks or had undergone stress corrosion cracking (SCC) attack and/or hydrogen embrittlement. Criteria for tube rejection. The optimal interval between repeated inspections (monitoring) of the reactor together with the time of analysis and decision. Criteria for acceptable flaw danger level that would allow continued use of tubes in operation for two years. It was established that a main crack in a system of micro-cracks under dynamic pulse loading could start to propagate earlier and faster, and reach greater lengths and take longer time to brake than an individual main crack. At the same time it was shown that the remaining lifetime could decrease significantly when a main crack interacts with a field of micro-cracks. The danger level (the J-integral value) of combined flaw increases significantly and may provoke dramatic failure within a few weeks. Therefore, only continued monitoring can eliminate the risk of tube fracture in this case. Tension tests, optical and electron fractography, micro-sclerometric and AE image recognition investigations, spectral and chemical analysis, TOFD, X-ray, all established a good correlation between the results obtained from steel specimens and full-size tube specimens tests, LDPE reactor tubes examinations and theoretical calculations.

Spectral density of "generation-recombination" noise voltage <δV²_gr> ("g-r noise") in Photoconductive Mercury-Cadmium Telluride / Hg_1-xCd_xTe (PC MCT) infrared radiation detectors with absorber n-Hg_1-xCd_xTe layer was calculated. Variations of <δV²_gr> with doping level (n ≈ Nd), ambient background flux density (Q_bgr, T_bgr ≈ 300 K), electrical bias (V_b/I_b) and design of sensitive pixel were analyzed. Spectral density of low-frequency noise as superposition of Flicker-noise "1/f", g-r noise resulting from fluctuations in generation-recombination rates of equilibrium (thermal) charge carriers <δV²_{gr, th}> and excess charge carriers exited by background photons <δV²_gr,bgr> and Johnson-Nyquist noise <δV²_JN> were examined in Hg_1-xCd_xTe photoconductors based on MBE-grown multi-layer structures. Noise measurements were performed on Long-Wave (LWIR) PC MCT detectors with responsivity peak wavelength 10 ≤ λ_p ≤ 12 μm at operating temperature Top ≈ 290-300 K and 78 K. Registration and recording of noise voltage spectral density graphs were performed in frequency range from 6 Hz to 12.5 kHz with resolution equals to 6 Hz. Tested PC MCT detectors show extremely low spectral density of excess Flicker-noise with cut-off frequency (F_co) ranging from 10 to 300 Hz. Measured dependencies of g-r noise voltage spectral density are correlated with calculations.

Influence of quantum dot growth on the electrical properties of Au/GaAs Schottky diode structures containing self-assembled InAs quantum dots fabricated via atomic layer molecular beam epitaxy is investigated. Current-voltage characteristics and low frequency noise measurements were performed and analyzed. Employing four different structures; containing single quantum dot layer, without quantum dot layer for a reference, thicker capping layer with single quantum dot layer, three quantum dot layers, we find the diode containing single quantum dot layer show largest leakage current and all the dots show 1/f behavior in low frequency noise characteristics. Current dependence of the noise current power spectral density shows that all the dots have linear current dependence at low bias which is explained by the mobility and diffusivity fluctuation. The Hooge parameter was determined to be in the range of 10^-7 to 10^-8. At high bias, the diodes containing quantum dot layer(s) show I_F^β dependence with the value of β larger than 2 (3.9, and 2.7), and the diode without quantum dot layer and thicker capping layer show the value of β smaller than 2 (1.6). The deviation of the values of β from two is explained by the random walk of electrons involving interface states at the metal-semiconductor Schottky barrier interface via barrier height modulation. It seems that the growth of quantum dots induces generation of the interface states with its density increasing towards the conduction band edge. The value of β smaller than 2 means that the interface states density is increasing towards the midgap. Typical value of the interface states density was found to be on the order of 10¹¹ to 10¹²cm²/Vs.

The error rate in a current-controlled logic processor dominated by shot noise has been investigated. It is shown that the error rate increases very rapidly with increasing cutoff frequency. The maximum clock frequency of the processor, which works without errors, is obtained as a function of the on-state current. The information channel capacity of the system is also studied.

This paper discusses the noise performance of a crystal oscillator. It is assumed that the crystal resonator motional losses, inductance, and capacity as well as its static capacity are flicker noisy. The Johnson thermal additive noise of the motional losses is also taken into account. To convert the intrinsic noise sources to the amplitude and phase fluctuations, the crystal resonator and the feedback amplifier are performed by noisy impedances. The crystal oscillator is reduced to the closed loop of the resonator impedance and the feedback amplifier impedance. The transformation coefficients are derived to convert the resonator and amplifier amplitude and phase power spectral density functions to those of the oscillator amplitude and phase. Noise performance of a crystal oscillator with different excitation angles of a resonator is studied in detail.

There have been many claims that quantum mechanics plays a key role in the origin and/or operation of biological organisms, beyond merely providing the basis for the shapes and sizes of biological molecules and their chemical affinities. These range from Schroedinger's suggestion that quantum fluctuations produce mutations, to Hameroff and Penrose's conjecture that quantum coherence in microtubules is linked to consciousness. I review some of these claims in this paper, and discuss the serious problem of decoherence. I advance some further conjectures about quantum information processing in bio-systems. Some possible experiments are suggested.