We discuss three control strategies aimed at countering the effects of decoherence: the first hinges on frequent projective measurements, the second on frequent unitary "kicks" ("bang-bang" pulses) and the third on a strong continuous coupling. Decoherence is suppressed if the frequency N of the measurements/kicks is large enough or if the coupling K is sufficiently strong: in all these cases, the Hilbert space of the system splits into invariant subspaces, among which any transition is hindered. However, if N or K are large, but not extremely large, all these control procedures accelerate decoherence.

We consider fundamental limits on information acquisition from localized regions of molecular-scale electronic systems. Our approach is based on a quantitative measure we call the volume accessible information, defined as the (Shannon) mutual information associated with the best possible quantum measurement that can access a system through a specified readout volume. Using results and techniques from quantum measurement theory, we obtain a general expression for an upper bound on the volume accessible information that depends only on the manner in which information is encoded in electron states and specification of the readout volume. An illustrative study of a model tight-binding system indeed reveals that the volume accessible information is sharply reduced at small sampling volumes, where the state distinguishability required for reliable information extraction is diminished.

There has been recent interest in implementing automated planning by optimizing a planning domain modeled as a stochastic system. Planning is viewed as a process where sequential decision problems are solved in order to reach the goal, and thus, can be considered as instances of a Markov Decision Process (MDP). However, standard MDP techniques cannot solve a typical planning problem in polynomial time. Hence, the motivation for investigating the use of quantum search techniques based on the Grover Search Algorithm, to identify policies with high utility.

We analyze the newly proposed quantum feedback loop for a solid-state qubit, based on monitoring the quadrature components of the current from a weakly coupled detector, which continuously measures the qubit. Similar to the earlier proposal of the "Bayesian" feedback, the feedback loop is used to maintain the coherent (Rabi)oscillations in a qubit for an arbitrarily long time; however, this is done in a significantly simpler way, which requires much smaller bandwidth of the control circuitry. The price for simplicity is a less-than-ideal operation: the fidelity is limited to about 95%. The feedback loop operation can be experimentally verified by appearance of a positive in-phase component of the detector current relative to an external oscillating signal used for synchronization. The quadrature-based quantum feedback seems to be within the reach of the present-day technology.

Electrochemical noise (EN) has been intensively investigated for the last few decades. There are practical applications of EN measurements for corrosion recognition but the phenomenon needs still further research. The experimental results of correlation between the surface damages of the metal electrodes and the intensity of voltage fluctuations observed between two nominally identically prepared electrodes are presented. The sets of carbon steel electrodes were applied. Only the metal surfaces were exposed to the electrolyte. The low-frequency voltage noise was continuously registered and the pictures of the electrode surfaces were taken every 30 minutes. The pits, which were created on the metal surface, were detected by Matlab software and compared with the statistical parameters of the observed voltage noise. The acts of the individual pits creation were strictly related to the presence and intensity of transients, characteristic for meta-stable pitting processes in carbon steel. The experimental setup is described. Some detailed remarks according to the applied detection algorithms of the metal damage are also included.

In this paper a statistical model for noisy data selection has been presented. It combines two powerful tools: a local wavelet analysis and multidimensional data analysis of wavelet transform coefficients. In the proposed model the adapted Malvar wavelet transform has been applied. It leads to a partition of the measuring signal to isolate transients. The multidimensional wavelet coefficients analysis has been applied to constitute a set of discriminating parameters that can be used to explore features characterizing transients caused by the air bubbles from diver's oxygen tanks.

In this paper it is discussed the efficiency of harmonics detection in the precence of Gaussian noise by applying bispectrum function (higher-order spectrum). The proposed method is compared with the effectiveness obtained by the classical method that implements power spectrum density. The main results reported in this paper are, first, confirmation that the bispectrum function can reveal the harmonics overwelmed by Gaussian noise and, second, how this method is limited in practice. The details of the applied procedure are presented and discussed due to the random error of the bispectrum estimator and its method of calculation. The principles of the higher-order spectrum analysis are also pointed out.

Nonlinear processes are often encountered in the practice of electrochemical corrosion measurements. Especially, activation controlled processes are inherently nonlinear. In the investigations of electrode reactions linear approximation is common approach. In this introductory paper the possibility of extension of electrochemical noise measurements to the nonlinear regime is presented. The authors focus on the case of cathodic polarization of electrochemical systems what is extremely important for corrosion protection.

Phonons, i.e. quanta of lattice vibrations, manifest themselves practically in all electrical, thermal, optical and noise phenomena in semiconductors and other material systems. Reduction of the size of electronic devices below the acoustic phonon mean free path creates a new situation for the phonons propagation and interaction. From one side, it may complicate heat removal from the downscaled devices. From the other side, it opens up an exciting opportunity for re-engineering phonon spectrum in nanostructured materials, and achieving enhanced operation of nano-devices. Since phonon-assisted tunneling and carrier scattering on phonons affect the charge carrier transport, modification of the phonon spectrum is also expected to influence noise level in nano-devices. This paper reviews the development of the phonon-engineering concept and discusses its device applications. The focus of this review is on tuning the phonon spectrum in acoustically mismatched nano- and heterostructures in order to change the ability of semiconductors to conduct heat and electric current. New approaches for the electron-phonon scattering rates suppression and the carrier mobility enhancement are also discussed. The last section of this review describes our recent results on phonons in the rod-shaped viruses used as biological nano-templates for self-assembly of nanoelectronic circuits.

A variety of noise measurements have been accomplished on electronic devices incorporating individual single-walled carbon nanotubes. Noise with a 1/f frequency dependence and noise attributed to two-level fluctuators are independently measured, even when these two components occur simultaneously in the same device. We demonstrate the importance of isolating these two components before attempting quantitative analysis, and then proceed to characterize devices as a function of temperature and processing history. High temperature desorption, surface passivation with polymer, and encapsulation in SiO2 films followed by forming gas annealing are three different process pathways which failed to substantially decrease the noise in these devices. In all of the devices measured, the 1/f noise components are found to only weakly decrease with temperature and to be practically independent of processing history. The two-level fluctuators, on the other hand, appear to be thermally activated and their contribution to the total noise typically increases with different processing steps.

In this paper the energy of an electron excited in conduction state in benzene (C₆H₆) molecule is estimated. The possible energy of the excited electron depends on the eigen energy state of the excited electron. Estimation of energy of an electron excited in conduction in C₆H₆ molecule is necessary to analyze fluctuation in currents in benzene molecule. Stable current-voltage (I-V) behavior of benzene molecule ensures functionality of any nano device involving benzene molecule or its derivative. This theoretical work can be verified by experiment of radiation from an excited benzene molecule. The result will give precise idea about the energy needed to destabilize the electrical behavior of devices made of benzene molecules. Benzene molecule is interseting for its potential in molecular nano electronics. The hexagonal core plane of the benzene molecule is relatively unalterable compared to the π localized electrons. Disturbance in the π-electron cloud will cause creation of hole by exciting a π electron to jump for conduction or may push an excited electron in the π electron cloud. The analysis of these effects rely on estimates of the energy imbalance due to presence of excited charged particles. This work is a beginning step in this front. The knowledge can be used to engineer improved switching mechanism using benzene molecule as an electronic device.

Spectral density of "generation-recombination" noise voltage <δV²gr> ("g-r noise") in photoconductive Hg_1-xCd_xTe infrared radiation detectors with absorber n-Hg_1-xCd_xTe layer was calculated. Variations of <δV²gr> with doping level (n ≈ N_d), ambient background flux density (Q_bgr, T_bgr ≈ 300 K), electrical bias (V_b/I_b) and pixel active area 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 small active area (30 μm x 30 μm and 50 μm x 50 μm) 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 T_op ≈ 78 K. Measured dependencies of g-r noise voltage spectral density have confirmed BLIP mode of photoconductors up to FOV=10 degrees where D*(λ_p) exceed 2x10¹¹ Jones.

Fatal injury of bacteria opens transmembrane ion pathways that create temporary ion clouds around the cells. This ion release transiently charges bacteria yielding spatiotemporal fluctuations of the electrical field which show up like a "fatal scream" in thermal noise. The effect has recently been demonstrated with the specific injuries caused by bacteriophage infections (King, et al, in press) and suggested for identification of bacteria with extraordinary speed and selectivity. Calculations indicate that the detection and identification of a single bacterium can be achieved with natural (wild) phages with reasonable efforts within a time window of 10 minutes. However the potential applicability of the agent-triggered ion cascade reaches much beyond that, including other kinds of injuries, such as those induced by antibiotics, ageing, poisoning, etc. Considerations and open questions about the physical aspects of the fluctuations and their detectability are discussed in this talk.

Detecting quantum fluctuations of a mechanical resonator is a long-standing goal of experimental physics. Recent progress has been focussed on high frequency (MHz to GHz) resonators inserted in a milli-Kelvin environment, with motion detection performed by single electron transistor means. Here we propose a novel experimental approach based on high-sensitivity optical monitoring of the displacement of the resonator and feedback cooling. The experimental setup is based on a micro-mechanical resonator inserted in a high-finesse optical cavity and monitored by a highly-stabilized laser system. Available optical technologies provide an unequalled sensitivity, in the 10^-20m/√Hz range. The displacement signal is used in real-time to perform a feedback cooling in order to set the resonator's fundamental mode of vibration in its quantum ground state. With the resonator at cryogenic temperature, the feedback cooling mechanism should allow to reach an effective temperature in the micro-Kelvin range.

We present measurements of noise induced switching for a system far from equilibrium. The system under study is an underdamped micromechanical torsional oscillator driven into the nonlinear regime. Under a sufficiently large periodic driving field, the oscillator has two stable dynamical states with different oscillation amplitudes within a certain range of driving frequencies. We induce the oscillator to escape from one dynamical state into the other by introducing noise in the excitation. By measuring the rate of random transitions as a function of noise intensity, we demonstrate the activated behavior of escape from the high-amplitude state to the low-amplitude state.

Multiplicative noise in the equation of motion of an overdamped oscillator leads to a series of new effects. These include the shift of stable points and stochastic resonance in linear system, noise enhanced stability and stabilization of metastable states in the non-linear single well model, resonance activation and coherent resonant activation in the non-linear double well model. The classical theoty of Brownian motion is supplemented by its applications to anomalous diffusion and to the special case of Brownian motion near the critical point

Microfabricated magnetoresistive zigzag-shaped elements based on the anisotropic magnetoresistance effect were studied for use as magnetic field sensors. Images taken using scanning electron microscopy with polarization analysis show that the magnetization in the devices tends to follow the edges of the device, thereby providing a geometrical (45°) bias that alternates along length of the sensor. It was found that these devices are primarily sensitive to magnetic fields applied along the long axis; a flat response is observed for perpendicular fields. The alternating magnetization bias provides the directionality of the sensor because the angles in adjacent zigzag blocks scissor for fields parallel to the long axis and rotate for perpendicular fields. This results in resistances that either add or cancel, respectively. A single-domain, coherent rotation description provides an estimate for the qualitative behavior of these zigzag structures and indicates the possible role of exchange in the shape of the transfer curves. Noise measurements were also taken on these devices. Thermal resistance noise was the dominant noise source above about 10 kHz. At low frequencies the resistance noise was found to be dominated by a 1/f contribution that depends on the applied magnetic field. The 1/f noise is relatively low and field independent when the element is in a saturated magnetic state and contains a relatively large and field dependent excess contribution when the magnetic field is in the sensitive field range of the element. The 1/f noise level observed in the saturated state depends in a nontrivial way on the quality and processing of the magnetic element, showing a trend for lower normalized noise in elements having higher sensitivity. In the most sensitive elements (magnetoresistance > 1%) the 1/f noise level is comparable to that found in nonmagnetic metals. We attribute the origin of noise to defect motion. In the unsaturated state, the excess noise is found to track the dc resistance susceptibility. For particular values of applied field we also observed large random telegraph signals in the time domain. The telegraph noise was extremely sensitive to the applied field, becoming active and inactive in our measurement bandwidth for changes in field of only a few Oersteds. This behavior indicates a magnetic origin to the excess noise. The variation of the excess noise level with applied dc magnetic field can be explained qualitatively using a model based on thermal excitation of the magnetization direction and/or domain wall hopping between pinning sites.

The principles of the construction of piezoresistive silicone pressure sensors are outlined. The fabrication of sensors with ion-implantation and common silicone wafer technology is described. The simulation of the devices showed that the membrane thickness has a major influence on the sensitivity, while the misalignment is less important. The low-frequency noise spectra of the piezoresistive elements are Lorenzian; the characteristic time constant is about 23 μs. The bias dependence of the spectra is in some degree less than it was expected from the regular V2 scaling. The plateau of the noise spectrum at working conditions is higher with almost 30 dB than the thermal noise. This excess noise is attributed to a trap level; however the origin of this G-R center is not clear yet. The figures of merits of the sensor were also estimated in numerical examples.

This paper presents an accurate temporal noise analysis of a new kind of CMOS image sensor for colour design. Operating in the charge storage mode, the noise of this APS is described with a time-varying model. During the reset phase, as the steady state is fast established, classical frequency-domain noise analysis can still be used to determine noise at both sensing nodes. Good agreement is observed between the results obtained by simulation with Cadence CAD tools of a 0.35μm-CMOS test structure and the behaviour predicted by the proposed analytical approach. During the integration phase, as both junctions are floating, the stationary state condition is never fulfilled and the noise analysis must be carried out in the time-domain. Our contribution consists in taking into account the non-linearity of the junction capacitance, which yields more realistic results. Considering only the dominant white noise component, it clearly appears that the junction non-linearity improves the output SNR for both sense nodes at high illumination and/or high integration period.

The influence of the surface and interfaces of semiconductor-metal Al/n⁺Si-nSi/Al and Ag/n⁺Si-nSi/Ag structures with different aluminum and silver contact coating layers on the level and behavior of the low frequency current noise spectra was experimentally investigated. It is shown that the level of low frequency noise strongly depends on the material and form of the contact coating layers. At the room temperature, at the frequency 10 Hz, the noise level for Al/n⁺Si-nSi/Al structures is equal to ~ 10^-15 A²/Hz, for the Ag/n⁺Si-nSi/Ag structures is equal to ~ 10^-17-10^-18 A²/Hz. It seems possible that the interface conditions modification, which in its turn mirrors at the processes of surface reflection and refraction of electrons and phonons, affects on the relaxation processes of longer-wavelength electron distribution function fluctuation and thus on mobility fluctuation and 1/f noise level as well. On the base of noise spectral characteristics of the mentioned structures the peculiarities of the acoustic phonons refraction on the semiconductor-metal flat interface are experimentally investigated. Several practical aspects related with so-called "refraction points" are discussed. It is proposed that, by manipulation of those phonons "refraction points" at hetero-interface, it will be possible to suppress the part of 1/f noise level, which arises in the volume of semiconductor. It is supposed that the hetero-interface by itself is not the source ("generator") of the 1/f noise, but probably is a factor of the volume 1/f -noise "reduction".

We propose a new way of pattern recognition which can distinguish different stochastic processes even if they have the same power density spectrum. Known crosscorrelation techniques recognize only the same realizations of a stochastic process in the two signal channels. However, crosscorrelation techniques do not work for recognizing independent realizations of the same stochastic process because their crosscorrelation function and cross spectrum are zero. A method able to do that would have the potential to revolutionize identification and pattern recognition, techniques, including sensing and security applications. The new method we are proposing is able to identify independent realizations of the same process, and at the same time, does not give false alarm for different processes which are very similar in nature. We demonstrate the method by using different realizations of two different types of random telegram signals, which are indistinguishable with respect to power density spectra (PDS). We call this method bispectrum correlation coefficient (BCC) technique.

This study is carried out to investigate the temperature dependence of fluctuation-enhanced sensor signals in Taguchi sensors. Sensor resistances measured at 20 Hz in the SP sensors manufactured by FIS Inc. and TGS sensors manufactured by Figaro Inc. have been analyzed. An empirical formula has been developed for calculating the temperature dependence. The empirical formula has the potential of application in real-time sensor signal processing and the optimization of temperature for the best sensing performance.

The original quantum eraser scheme [Scully and Druhl, Phys. Rev. A 25, 2208 (1982)] is based on the entanglement of the two sequentially and spontaneously emitted photons. We consider the scheme in which the first emitted photon is largely detuned from resonance. We use the Schrodinger equation approach and the Laplace transform method to obtain the Raman Emission Doublet(RED) state vector. An exact analytical expression for the two-photon correlation function is derived in a general form that applies to any polarization of the two detectors located at any position, including the near field regime where the distances are comparable to the wavelengths of the photons. Frequency dependent refractive indexes of the RED photons are also included.