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The self-energy in Born approximation including exchange of interacting one-dimensional systems is expressed in terms of a single integral about the potential which allows a fast and precise calculation for any potential analytically. The imaginary part of the self-energy as damping of single-particle excitations shows a rich structure of different areas limited by single-particle and collective excitation lines. The corresponding spectral function reveals a pseudogap, a splitting of excitations into holons and antiholons as well as bound states. [ABSTRACT FROM AUTHOR]

For the first time to our knowledge, the turbo-switched Mach–Zehnder interferometers (TS-MZIs) architecture, which includes quantum-dot semiconductor optical amplifiers (QDSOAs) and is followed by a series delayed interferometer (DI), is used in a combined scheme (QDSOAs-TS-MZIs-DI) to realise NOT-AND (NAND) and exclusive-NOR (XNOR) Boolean functions at a rate of 1 Tb/s return-to-zero data. The performance of the two considered gates is evaluated by calculating and comparing the quality factor and the cross-correlation coefficient for the QDSOAs-TS-MZIs-DI, the TS-MZIs with QDSOAs but without DI (QDSOAs-TS-MZIs) and the standard MZIs with QDSOAs (QDSOAs-MZIs). The comparison shows the superiority of the QDSOAs-TS-MZIs-DI over the other two alternatives (QDSOAs-TS-MZIs and QDSOAs-MZIs) and hence suggests that it should be preferred as a switching module when executing the NAND and XNOR Boolean functions at 1 Tb/s in the optical domain. [ABSTRACT FROM AUTHOR]

This paper compared the results of Gaussian, Shannon, and Tsallis entropies in the study of the decoherence of magnetopolaron in nanostructures in the presence of an electric field. The unitary transformation and linear combination method are used to derive the energy spectrum of the magnetopolaron in Gaussian and asymmetric quantum dot. Results suggest that Shannon entropy is suitable for the faster transmission of information about the system. With the increase in the strength of electric field and cyclotron frequency, the collapse revival in entropy is observed. With the asymmetric quantum dot, one realizes that the amount of information indicated by Shannon entropy is efficient than with other entropies. With the enhancement of the electric field strength, the entropies evolve as a wave envelop, and the information is transmitted as a wave bundle. [ABSTRACT FROM AUTHOR]

Recently, Xu et al. [Phys. Rev. A 2012, 86, 012113] have explored the behaviour of the entropic uncertainty relation under the influence of local unital and nonunital noisy channels for a class of Bell-diagonal states. We here improve their results and investigate the entropic uncertainty relation under the influence of unital and nonunital noisy channels with memory. Different types of noisy channels with memory, such as amplitude damping channel (nonunital channel), phase-damping and depolarizing channels (unital channels) have been taken into account. Analytical or numerical results is presented. The effect of channels with memory on dynamics of the entropic uncertainty (or its lower bound) has been discussed in detail. Compare with previous results, our results show that, the entropic uncertainty (or its lower bound) subjecting to amplitude damping channel with memory will be reduced at first and then be lifted with the memory coefficient of channel μ increasing, however they will be only reduced under phase-damping and depolarizing channels in the presence of memory. Especially, in the limit of , the entropic uncertainty (or its lower bound) could be well protected and immune to decoherence of channels. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the preservation of quantum Fisher information (QFI) of a single-qubit system coupled to a common zero temperature reservoir through the addition of noninteracting qubits. The results show that, the QFI is completely protected in both Markovian and non-Markovian regimes by increasing the number of additional qubits. Besides, the phenomena of QFI display monotonic decay or non-monotonic with revival oscillations depending on the number of additional qubits N − 1 in a common dissipative reservoir. If N < Nc (a critical number depending on the reservoirs parameters), the behavior of QFI with monotonic decay occurs. However, if N ≥ Nc, QFI exhibits non-monotonic behavior with revival oscillations. Moreover, we extend this model to investigate the effect of additional qubits and the initial conditions of the system on the geometric phase (GP). It is found that, the robustness of GP against the dissipative reservoir has been demonstrated by increasing gradually the number of additional qubits N − 1. Besides, the GP is sensitive to the initial parameter 휃, and possesses symmetric in a range regime [0,2π]. [ABSTRACT FROM AUTHOR]

An analytical study has been carried out on the InAs/GaAs p-i-n quantum dot solar cell, taking into consideration the contributions of each region of the cell to the total photocurrent. The expressions for the excess minority carrier concentration and photocurrent from the front and the rear regions of the device have been obtained and their variations with different device parameters have been studied. Also, based on the investigations reported by some researchers earlier, the photocurrent contribution from the intrinsic region of the solar has been studied, taking into account the quantum dot ensemble absorption coefficient, which depends significantly on the quantum dot size and size dispersion. It is observed that all the three regions of the cell contribute to the overall internal quantum efficiency (IQE) of the cell. The contribution of each region of the solar cell to the total IQE has been shown graphically. From these studies it is observed that the incorporation of the quantum dots in the intrinsic region enhance the photocurrent density and hence the IQE of such solar cell, as it absorbs low energy photons, which are beyond the absorption range of GaAs. Finally, the fill factor of the solar cell has been calculated. [ABSTRACT FROM AUTHOR]

An electron strongly coupled to the LO-phonon in an asymmetric quantum dot has been considered. The system has a central impurity and it is under electric and magnetic fields. The eigenenergies and eigenfunctions of the ground and the first-excited states of the electron have been calculated using the Pekar variational method. Entropy of the system for different values of Coulomb impurity parameter, electron-LO phonon coupling strength, dispersion coefficient and electric field have been studied. Two entropies, Shannon and Gaussian entropy have been employed. It is found that the entropy has the oscillatory periodic evolution as function of the time due to the confinement form. It is deduced that the entropies increase with enhancing Coulomb impurity parameter, electron-LO phonon coupling strength and dispersion coefficient. With increasing electron-LO phonon coupling strength, the entropies decrease. The control of the coherence of the system can be done with the modulation of the electric field, the Coulomb bound potential, dispersion coefficient and electron-LO phonon coupling strength. [ABSTRACT FROM AUTHOR]

The behavior of the optical bistability (OB) and optical multi-stability (OM) is investigated in an optical system which consists of a dielectric slab doped with a three-level asymmetric semiconductor quantum well system. It is found that the optical bistability can be converted to optical multi-stability (or vice versa) by adjusting different physical parameters such as the strength of Fano interference and the rate of incoherent pump field. Moreover, we find that the OB converts to OM by increasing the slab thickness. This optical system may provide some new possibilities for test the switching process. [ABSTRACT FROM AUTHOR]

We report on the demonstration of substrate-free nanowire/polydimethylsiloxane (PDMS) membrane light-emitting diodes (LEDs). Metal-organic vapour-phase epitaxy (MOVPE)-grown InGaN/GaN core-shell nanowires were encapsulated into PDMS layer. After metal deposition to p-GaN, a thick PDMS cap layer was spin-coated and the membrane was manually peeled from the sapphire substrate, flipped upside down onto a steel holder, and transparent indium tin oxide (ITO) contact to n-GaN was deposited. The fabricated LEDs demonstrate rectifying diode characteristics. For the electroluminescence (EL) measurements, the samples were manually bonded using silver paint. The EL spectra measured at different applied voltages demonstrate a blue shift with the current increase. This shift is explained by the current injection into the InGaN areas of the active region with different average indium content. [ABSTRACT FROM AUTHOR]

Results on the temperature dependence of the threshold current density for semiconductor lasers based in different materials are presented, emphasizing in GaInNAs devices. In this case the model considers, the radiative, mono-molecular and Auger recombination components. The monomolecular recombination coefficient (Am) was taken independent of temperature; while the radiative coefficient (Br) was taken as Br≈T-1 and for Auger coefficient (CA) an exponential dependence was considered. These coefficients were used as adjustable parameters in the simulation. Results shown that while the monomolecular recombination is the main mechanism responsible for the increment of the threshold current with temperature the Auger component should be considered in all cases although with different weight related with the structure. [ABSTRACT FROM AUTHOR]