Effect of Static Disorder in an Electron-Fabry Perot Interferometr with Two Quantum Scattering Centers

In a recent paper -- F. Ciccarello \emph{et al.}, New J. Phys. \textbf{8}, 214 (2006) -- we have demonstrated that the electron transmission properties of a one-dimensional (1D) wire with two identical embedded spin-1/2 impurities can be significantly affected by entanglement between the spins of the scattering centers. Such effect is of particular interest in the control of transmission of quantum information in nanostructures and can be used as a detection scheme of maximally entangled states of two localized spins. In this letter, we relax the constraint that the two magnetic impurities are equal and investigate how the main results presented in the above paper are affected by a static d…

Physical model for the generation of ideal resources in multipartite quantum networking

We propose a physical model for generating multipartite entangled states of spin-$s$ particles that have important applications in distributed quantum information processing. Our protocol is based on a process where mobile spins induce the interaction among remote scattering centers. As such, a major advantage lies on the management of stationary and well separated spins. Among the generable states, there is a class of $N$-qubit singlets allowing for optimal quantum telecloning in a scalable and controllable way. We also show how to prepare Aharonov, W and Greenberger-Horne-Zeilinger states.

Plasma emission at the laser tripled frequency

The third harmonic generation in the skin-layer of a dense hot plasma due to inverse bremsstrahlung is investigated for regimes having increasing experimental relevance. New analytical dependencies of the radiation flux density at the frequency 3ω on the plasma and fundamental wave parameters are established.

Unusual optical properties in ultra short laser pulse interaction with dense nonequilibrium plasma

Wave-mixing effects on electronic noise in semiconductors

The results of a Monte Carlo analysis of hot-electron intrinsic noise in a n-type GaAs bulk driven by two mixed large-amplitude alternating electric fields having frequency in the subterahertz range are presented. The noise properties are investigated by studying the velocity autocorrelation function and the noise spectrum. We explored the relations among the frequency response and the velocity fluctuations as a function of the frequencies and intensities of the mixed fields. When the semiconductor is driven by two mixed ciclostationary electric fields, a resonant-like enhancement of the spectra near the two frequencies of the applied fields is found.

Assessment of knowledge state of physics students: ToL as evaluation tool in the Engineering faculty of Palermo University

Hot-electron noise suppression in n-Si via the Hall effect

We investigate how hot-electron fluctuations in n-type Si are affected by the presence of an intense (static) magnetic field in a Hall geometry. By using the Monte Carlo method, we find that the known Hall-effect-induced redistribution of electrons among valleys can suppress electron fluctuations with a simultaneous enhancement of the drift velocity. We investigate how hot-electron fluctuations in n-type Si are affected by the presence of an intense (static) magnetic field in a Hall geometry. By using the Monte Carlo method, we find that the known Hall-effect-induced redistribution of electrons among valleys can suppress electron fluctuations with a simultaneous enhancement of the drift vel…

CHANGES OF ELECTRONIC NOISE INDUCED BY OSCILLATING FIELDS IN BULK GaAs SEMICONDUCTORS

A Monte Carlo study of hot-electron intrinsic noise in a n-type GaAs bulk driven by one or two mixed cyclostationary electric fields is presented. The noise properties are investigated by computing the spectral density of velocity fluctuations. An analysis of the noise features as a function of the amplitudes and frequencies of two applied fields is presented. Numerical results show that it is possible to reduce the intrinsic noise. The best conditions to realize this effect are discussed.

Entanglement controlled single- electron transmittivity

We consider a system consisting of single electrons moving along a 1D wire in the presence of two magnetic impurities. Such system shows strong analogies with a Fabry - Perot interferometer in which the impurities play the role of two mirrors with a quantum degree of freedom: the spin. We have analysed the electron transmittivity of the wire in the presence of entanglement between the impurity spins. The main result of our analysis is that, for suitable values of the electron momentum, there are two maximally entangled state of the impurity spins the first of which makes the wire transparent whatever the electron spin state while the other strongly inhibits the electron transmittivity. Such…

Monte Carlo simulation of high‐order harmonics generation in bulk semiconductors and submicron structures

To qualify the feasibility of standard semiconductor materials and Schottky‐barrier diodes (SBDs) for THz high‐order harmonic generation and extraction, the harmonic intensity, intrinsic noise and signal‐to‐noise ratio are calculated by the Monte Carlo method when a periodic high‐frequency large‐amplitude external signal is applied to a semiconductor device. Due to very high signal‐to‐noise ratio heavily doped GaAs SBDs are found to exhibit conditions for frequency mixing and harmonic extraction that are definitively superior to those of bulk materials. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Transverse velocity fluctuations of hot electrons in n-type GaAs in crossed electric and magnetic fields by Monte Carlo methods

In this work we investigate some steady‐state stochastic properties of hot electron dynamics in bulk n‐type GaAs in the presence of crossed, static electric and magnetic fields. To this aim, a single particle, three valleys‐Monte Carlo method is adopted. In order to include the non‐parabolicity of valleys a local parabolic approximation is performed allowing us to get an analytic expression for k(t) during free flights. It is shown how the room temperature‐spectrum of longitudinal velocity fluctuations is markedly affected by the oscillations at the cyclotron frequency and is lowered or increased by the magnetic field depending on the considered frequency. On the contrary, the transverse sp…

Quasideterministic realization of a universal quantum gate in a single scattering process

We show that a flying particle, such as an electron or a photon, scattering along a one-dimensional waveguide from a pair of static spin-1/2 centers, such as quantum dots, can implement a CZ gate (universal for quantum computation) between them. This occurs quasi-deterministically in a single scattering event, hence with no need for any post-selection or iteration, {and} without demanding the flying particle to bear any internal spin. We show that an easily matched hard-wall boundary condition along with the elastic nature of the process are key to such performances.

Entanglement-induced electron coherence in a mesoscopic ring with two magnetic impurities

We investigate the Aharonov-Bohm (AB) interference pattern in the electron transmission through a mesoscopic ring in which two identical non-interacting magnetic impurities are embedded. Adopting a quantum waveguide theory, we derive the exact transmission probability amplitudes and study the influence of maximally entangled states of the impurity spins on the electron transmittivity interference pattern. For suitable electron wave vectors, we show that the amplitude of AB oscillations in the absence of impurities is in fact not reduced within a wide range of the electron-impurity coupling constant when the maximally entangled singlet state is prepared. Such state is thus able to inhibit th…

Laser even harmonics generation by a plasma embedded in a static electric field

Even order harmonics generation of the laser radiation due to electron-ion collisions in a plasma embedded in a constant electric field is investigated theoretically. Even harmonics are generated because the presence of a static electric field removes the invariance of the electron distribution function under the symmetry operation of velocity direction inversion. Efficiency generation dependencies are investigatedvsdifferent significant parameters as: harmonics number; the ratio of the electron quiver velocity to the thermal velocity; the orientation of the constant electric field with respect to the laser radiation electric field and its wavevector. It is shown that in the general case th…

Monte Carlo Calculation of Voltage-Current Nonlinearity and High-Order Harmonic Generation in GaAs Microstructures

Infrared radiation harmonic generation in degenerate semiconductors

The basic properties of infrared laser radiation odd harmonic generation due to electron-charged impurity collisions in degenerate semiconductors are investigated. It is found that in the case of relatively weak fields, the electron Fermi distribution is the cause of an anomalous suppression of harmonic radiation. In the case of strong fields, the effect of the selective suppression of single harmonics is established.

Monte Carlo analysis of electronic noise in semiconductors under sub‐terahertz cyclostationary mixed fields

This paper reports the results of Monte Carlo simulations of electronic noise in a GaAs bulk driven by two mixed high-frequency large-amplitude periodic electric fields. Under these conditions, the system response shows some peculiarities in the noise performance, such as a resonant-like enhancement of the spectra near the two frequencies of the applied fields. The relations among the frequency response and the velocity fluctuations as a function of intensities and frequencies of the sub-terahertz mixed excitation fields have been investigated. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

High-frequency even harmonics generation in a plasma with electron heat flux

It is shown that in a weakly nonuniform plasma with electron heat flux the generation of odd and even harmonics of high frequency radiation is possible. The even harmonics properties qualitatively differ as compared to those of odd harmonics and depend in an essential way on the heat flux value and orientation with respect to the fundamental wave polarization and propagation directions.

Reducing quantum control for spin - spin entanglement distribution.

We present a protocol that sets maximum stationary entanglement between remote spins through scattering of mobile mediators without initialization, post-selection or feedback of the mediators' state. No time-resolved tuning is needed and, counterintuitively, the protocol generates two-qubit singlet states even when classical mediators are used. The mechanism responsible for such effect is resilient against non-optimal coupling strengths and dephasing affecting the spins. The scheme uses itinerant particles and scattering centres and can be implemented in various settings. When quantum dots and photons are used a striking result is found: injection of classical mediators, rather than quantum…

Generation of even harmonics of sub-THz radiation in bulk GaAs in the presence of a static electric field

The static electric field effects on nonlinear carrier dynamics in low-doped GaAs bulk under the influence of an intense sub-terahertz field are studied by a three-dimensional multivalleys Monte Carlo simulation. The conversion efficiency is calculated by using the appropriate Maxwell equation for the propagation of an electromagnetic wave along a given direction in the medium. Production of odd and even harmonics due to the nonlinearity of the velocity-field relation is investigated.

Hydrodynamic Modeling of Transport and Noise Phenomena in Bipolar Two-Terminal Silicon Structures

International audience

Even harmonics generation in plasma as a new tool of current evolution diagnostics

It is shown that using even harmonics of a test wave it is possible to diagnose the fast time evolution of the current density.

Even harmonics generation of high frequency radiation in current-carrying plasmas

Generation of high frequency radiation harmonics in a current-carrying plasma is studied. The physical mechanism responsible for harmonics generation is provided by electron-ion collisions. The current in the plasma is sustained by a constant electric field. It is shown that the electron distribution function anisotropy due to the static field yields generation of even harmonics. As a result, the radiation spectrum emitted by the current-carrying plasma contains both even and odd harmonics, the latter being attributed to currentless plasma. For a broad range of plasma and high frequency radiation parameters, a detailed analysis of the even harmonics properties is reported.

Rising time of entanglement between scattering spins,

We investigate the time evolution of entanglement in a process where a mobile particle is scattered by static spins. We show that entanglement increases monotonically during a transient and then saturates to a steady-state value. For a quasi-monochromatic mobile particle, the transient time depends only on the group-velocity and width of the incoming wavepacket and is insensitive to the interaction strength and spin-number of the scattering particles. These features do not depend on the interaction model and can be seen in various physical settings.

Valutazione dell’apprendimento in fisica mediante ToL (Test on Line): la sperimentazione al Politecnico di Torino e all’Università di Palermo.

Anomalous properties of hot dense nonequilibrium plasmas

A concise overview of a number of anomalous properties of hot dense nonequilibrium plasmas is given. The possibility of quasistationary megagauss magnetic field generation due to Weibel instability is discussed for plasmas created in atom tunnel ionization. The collisionless absorption and reflection of a test electromagnetic wave normally impinging on the plasma with two-temperature bi-maxwellian electron velocity distribution function are studied. Due to the wave magnetic field influence on the electron kinetics in the skin layer the wave absorption and reflection significantly depend on the degree of the electron temperature anisotropy. The linearly polarized impinging wave during reflec…

Dynamical effects and Terahertz harmonic generation in low-doped bulk semiconductors and submicron structures

We present results obtained using a three-dimensional multivalleys Monte Carlo (MC) model to simulate the nonlinear carrier dynamics under the influence of an intense sub-terahertz electric field in a doped bulk semiconductor. By self-consistently coupling a one-dimensional Poisson solver to the ensemble MC code we simulate also the nonlinear carrier dynamics in n+nn+ structures operating under large-amplitude periodic signals and investigate the voltage-current characteristic hysteresis cycle and the high-order harmonic efficiency. For both cases we discuss the dependence of the nonlinearities and of the harmonic generation efficiency on the frequency and the intensity of the alternating s…

Electronic Noise in Semiconductor Systems: a Monte Carlo Simulation under Mixed Fields

Third-harmonic generation in the skin layer of a hot dense plasma

The third-harmonic generation of a pump wave, resulting from the electron-ion collision frequency dependence on the electric field in the skin layer of a hot dense plasma is investigated. The relation of the current third harmonic with the high-frequency field in the skin layer is established for arbitrary ratios of the electron-ion collision frequency to the field frequency. For arbitrary ratios of these two frequencies, the field structure inside the skin layer is determined, and the field of the wave irradiated by the plasma at tripled frequency, too, is calculated. It has permitted us to find the explicit dependencies of the third-harmonic generation efficiency on the plasma and pump fi…

Monte Carlo Analysis of Voltage-Current Characteristic Nonlinearity and Harmonic Generation in Submicron Semiconductor Structures

Using a multiparticles Monte Carlo technique, we investigate the dependence of the nonlinear carrier dynamics in GaAs n+nn+ structures operating under very intense sub-terahertz signals from some process parameters as: i) the frequency and the intensity of the excitation signal and ii) the length of the n region

Third harmonic generation in the skin layer of a hot dense plasma

The third harmonic generation of a pump wave, resulting from the electron-ion collision frequency dependence on the electric field in the skin-layer of a hot dense plasma is investigated. The relation of the current third harmonic with the high-frequency field in the skin-layer is established for arbitrary ratios of the electron-ion collision frequency to the field frequency. For arbitrary ratios of these two frequencies the field structure inside the skin-layer is determined, and the field of the wave irradiated by the plasma at tripled frequency too is calculated. It has permitted to find the explicit dependencies of the third harmonic generation efficiency on the plasma and pump field

Monte Carlo Analysis of Voltage-Current Characterstic Nonlinearity and Harmonic Generation in Submicron Semiconductor Structures

Langevin approach to collisional bremsstrahlung in a magnetic field

Even and Odd Harmonic Generation in low-doped semiconductors

Nonlinear Current Generation in Degenerate Semiconductors Embedded in Constant and Low-Frequency Electric Fields

The explicit analytical forms of nonlinear currents in degenerate semiconductors serving as sources of coherent radiation in the wavelength millimetric and submillimetric ranges are established.

Hot electron noise in n-type GaAs in crossed electric and magnetic fields

A Monte Carlo analysis of hot electron transport properties of bulk \textit{n}-type GaAs in crossed electric and magnetic fields is presented. %Magnetic field strengths allowing negligible quantum effects in the electron dynamics during free flights are considered. Effects due to the nonparabolicity of bands are properly taken into account by means of a local parabolic approximation. Stochastic properties of electron transport are analyzed by computing the velocity auto-correlation function and the spectral density of fluctuations. It is shown how the presence of the magnetic field is able to deeply modify electron noise up to high electric field strengths. The resulting features of the vel…

Anomalous properties of hot dense nonequilibrium plasmas

Hot electron noise in n-type semiconductors in crossed electroc and magnetic fields

Amplification of nonlinear currents generation at harmonics frequencies of submillimeter radiation

The conditions are found when rapid heating of the electrons of a degenerate semiconductor in the presence of two electric fields, one constant and the other variable, is accompanied by the formation of a distribution function significantly departing from the Fermi one. It is also shown that the newly found modification of the electron distribution yields a relative amplification of nonlinear currents generation.

Static-ElectricField Effects on harmonic generation in Gallium Arsenide Bulk exposed to intense sub-THz radiation

Field mixing influence on the hot-electron noise in Semiconductors

Monte Carlo Analysis of the efficiency of Tera-Hertz Harmonic Generation in semiconductors

Monte Carlo Simulation of Harmonic Generation in GaAs structures operating under large-signal Conditions

By using a multiparticles Monte Carlo technique, with a self-consistently coupled one-dimensional Poisson solver, we investigate the dependence of the nonlinear carrier dynamics in GaAs n+nn+ micro e submicro-structures operating under very intense sub-terahertz signals by: (i) the frequency and the intensity of the excitation signal and (ii) the length of the n region.

Electric conduction in semiconductors: a pedagogical model based on the Monte Carlo method

We present a pedagogic approach aimed at modelling electric conduction in semiconductors in order to describe and explain some macroscopic properties, such as the characteristic behaviour of resistance as a function of temperature. A simple model of the band structure is adopted for the generation of electron–hole pairs as well as for the carrier transport in moderate electric fields. The semiconductor behaviour is described by substituting the traditional statistical approach (requiring a deep mathematical background) with microscopic models, based on the Monte Carlo method, in which simple rules applied to microscopic particles and quasi-particles determine the macroscopic properties. We …

Unusual Optical Properties of the Dense Nonequilibrium Plasma

A concise overview of new optical properties of dense nonequilibrium plasma formed on the solid state target boundary is given. In this chapter, we describe phenomena such as the third harmonic generation in the skin layer, collisionless electron heating in the high frequency skin-effect regime, absorption, and reflection and transmission of radiation by a plasma with anisotropic electron distribution.

Plasma radiation spectra in the presence of static electric and high-frequency radiation fields

Harmonics generation of high-frequency radiation in a plasma embedded in a constant electric field is investigated theoretically. It is shown that the electron directed motion due to the static electric field yields the appearance in the plasma emission spectrum of high-frequency radiation even harmonics. The conditions are established when the even harmonics generation is as effective as that of the odd ones. At variance with the odd harmonics, the even harmonics polarization plane is found to rotate with respect to that of the fundamental field. The basic dependencies concerning the rotation angle and the generation efficiency on the plasma and field parameters are established.

Electron Fabry-Perot interferometer with two entangled magnetic impurities

We consider a one-dimensional (1D) wire along which single conduction electrons can propagate in the presence of two spin-1/2 magnetic impurities. The electron may be scattered by each impurity via a contact-exchange interaction and thus a spin-flip generally occurs at each scattering event. Adopting a quantum waveguide theory approach, we derive the stationary states of the system at all orders in the electron-impurity exchange coupling constant. This allows us to investigate electron transmission for arbitrary initial states of the two impurity spins. We show that for suitable electron wave vectors, the triplet and singlet maximally entangled spin states of the impurities can respectively…

Amplification of nonlinear currents generation at harmonics frequencies of submillimeter radiation

Entanglement generation between two spin-s magnetic impurities in a solid via electron scattering

Abstract We present a scheme for generating entanglement between two magnetic impurities in a solid-state system via electron scattering. The scheme applies to impurities of arbitrary quantum spin number. We show that resonance conditions yield generation of a maximally entangled state of the impurities' spins, regardless of the value of the electron–impurity coupling constant and the impurity spin quantum number. The mechanism behind the scheme is explained in terms of resonance-induced selection rules.

The impact of the pre-instructional cognitive profile on learning gain and final exam of physics courses: a case study.

The case study described in this paper investigates the relationship among some pre-instructional knowledge, the learning gain and the final physics performance of computing engineering students in the introductory physics course. The results of the entrance engineering test (EET) have been used as a measurement of reading comprehension, logic and mathematics skills and basic physics knowledge of a sample of 47 Computing Engineering freshmen at the University of Palermo (Italy). These data give a significant picture of the initial knowledge status of a student choosing engineering studies. The students' physics learning gain has been calculated using a standardized tool in mechanics: the fo…

Teleportation between distant qudits via scattering of mobile qubits

We consider a one-dimensional (1D) structure where non-interacting spin-$s$ scattering centers, such as quantum impurities or multi-level atoms, are embedded at given positions. We show that the injection into the structure of unpolarized flying qubits, such as electrons or photons, along with {path} detection suffice to accomplish spin-state teleportation between two centers via a third ancillary one. {No action over the internal quantum state of both the spin-$s$ particles and the flying qubits is required. The protocol enables the transfer of quantum information between well-seperated static entities in nanostructures by exploiting a very low-control mechanism, namely scattering.

Diffusion of neutrons by a slab of moderating material: an application of the Monte Carlo Method

An application of the Monte Carlo method to the diffusion of neutrons passing through a slab of a moderating material is presented. This method can be used as a tool to improve the student's comprehension of the statistical properties of many particle systems, showing the necessity of simulation procedures to obtain information on the expected results of real experiments. We have chosen a very simple example to illustrate it: the evaluation of the transmission, reflection and absorption probabilities of a monochromatic beam of neutrons diffusing through a slab of a moderator material. After a collision with a nucleus of the moderator the neutron may be either elastically scattered or captur…

Anisotropic laser plasmas: Non linear processes and properties

ToL in the Engineering Faculty of Palermo University

Implementing quantum gates through scattering between a static and a flying qubit

We investigate whether a two-qubit quantum gate can be implemented in a scattering process involving a flying and a static qubit. To this end, we focus on a paradigmatic setup made out of a mobile particle and a quantum impurity, whose respective spin degrees of freedom couple to each other during a one-dimensional scattering process. Once a condition for the occurrence of quantum gates is derived in terms of spin-dependent transmission coefficients, we show that this can be actually fulfilled through the insertion of an additional narrow potential barrier. An interesting observation is that under resonance conditions the above enables a gate only for isotropic Heisenberg (exchange) interac…

Even-harmonics generation in a plasma acted upon by a static electric field

Diffusion of neutrons by a slab of moderating material