The influences of an anisotropic parabolic potential on the quantum dot qubit* Zhao Cui-Lan(赵翠兰), Cai Chun-Yu(蔡春雨), Xiao Jing-Lin(肖景林)?

To study the influence of an anisotropic parabolic potential(APP)on the properties of a quantum dot(QD)qubit,we obtain the eigenenergies and eigenfunctions of the ground and first excited state of an electron,which is strongly coupled to the bulk longitudinal optical(LO)phonons,in a QD under the influence of an APP by the celebrated Lee–Low–Pines(LLP)unitary transformation and the Pekar type variational(PTV)methods.Then,this kind of two-level quantum system can be excogitated to constitute a single qubit.When the electron locates at the superposition state of its related eigenfunctions,we get the time evolution of the electron’s probability density.Finally,the influence of an APP on the QD qubit is investigated.The numerical calculations indicate that the probability density will oscillate periodically and it is a decreasing function of the effective confinement lengths of theAPPindifferentdirections.Whereasitsoscillatoryperiodisanincreasingoneandwilldiminishwithenhancing the electron–phonon(EP)coupling strength.     

量子棒中电子的跃迁谱线的频率

The Hamiltonian of a quantum rod with an ellipsoidal boundary is given after a coordinate transformation which changes the ellipsoidal boundary into a spherical one. We then study the first internal excited state energy, the excitation energy and the frequency of the transition spectral line between the first internal excited state and the ground state of the strong-coupling polaron in a quantum rod. The effects of the electron–phonon coupling strength, the aspect ratio of the ellipsoid, the transverse radius of quantum rods and the transverse and longitudinal effective confinement length are taken into consideration by using a linear combination operator and the unitary transformation methods. It is found that the first internal excited state energy, the excitation energy and the frequency of the transition spectral line are increasing functions of the electron–phonon coupling strength, whereas they are decreasing ones of the transverse radius of quantum rods and the aspect ratio. The first internal excited state energy, the excitation energy and the frequency of the transition spectral line increase with decreasing transverse and longitudinal effective confinement length. oindent     

Dynamic nuclear self-polarization of Ⅲ-Ⅴ semiconductors

Ⅲ-Ⅴ semiconductors exhibit dynamic nuclear self-polarization (DYNASP) owing to the contact hyperfine interaction (HFI) between optically excited conduction electrons and lattice nuclei.In the self-polarization process at a low temperature,electron spin state and the nuclear polarization (magnetization) exchange a positive feedback,increasing energy splitting of the conduction electron states,thereby a large nuclear polarization.This phenomenon was theoretically predicted previously for conduction electrons excited linearly and elliptically polarized light.The polarization of the conduction electrons was represented by a parameter α in a formula for nuclear polarization (Eq.(9) in Ref.[1]);however,the effect of external magnetic fields on the nuclear polarization was not considered.Therefore,this study introduces this effect by further extending the previous studies.Herein,α'represents the combination of the effects of elliptically polarized electrons and an external magnetic field,which is used in the equations presented in previous studies.When α'=0,a large nuclear polarization is obtained below critical temperature Tc,but no polarization occurs above Tc.When α'＞ 0,the nuclear polarization is enhanced above Tc.Below Tc,the nuclear polarization follows a hysteresis curve when α'is partially manipulated by adjusting the degree of the polarization of the exciting laser.     

Lasing at a wavelength close to 1.3 µm in InAs quantum-dot structures

The feasibility of lasing at a wavelength close to 1.3 μm is demonstrated in InAs quantum-dot structures placed in an external InGaAs/GaAs quantum well. It is shown that the required wavelength can be attained with the proper choice of thickness of the InAs layer deposited to form an array of three-dimensional islands and with a proper choice of mole fraction of InAs in the InGaAs quantum well. Since the gain attained in the ground state is insufficient, lasing is implemented through excited states in the temperature interval from 85 K to 300 K in a structure based on a single layer of quantum dots. The maximum attainable gain in the laser structure can be raised by using three rows of quantum dots, and this configuration, in turn, leads to low-threshold (70 A/cm²) lasing through the ground state at a wavelength of 1.26 μm at room temperature. Fiz. Tekh. Poluprovodn. 33, 1020–1023 (August 1999)     

Utilization of triplet excited states in organic semiconductors

Organic optoelectronics is an emerging research field, which has attracted extensive interests in the last few decades owing to its practical applications, like organic light-emitting diodes (OLEDs), organic memory devices, organic photovoltaic (OPV), sensors, and organic field-effect transistors[1, 2]. Organic semiconductors play a crucial role in this field. Compared to the traditional inorganic semiconductors, organic semiconductors open a fascinating research direction because of some unique advantages, such as flexible design, low cost, and rich optical and electronic properties. In organic optoelectronics, the excited states greatly determine the photoelectronic properties and application areas as shown in Fig. 1. Based on the electron spin in the molecule, the excited states of organic semiconductors include singlet and triplet states. As we know, the radiative transitions of singlet and triplet excited states are always accompanied by fluorescence and phosphorescence emission, respectively.     

Controlled teleportation of an unknown 3D two-particle state via 3D partially entangled states

A scheme is presented to realize the controlled teleportation of an unknown three dimensional(3D) two-particle state by using a non-maximally entangled two-particle state and a non-maximally entangled three-particle state in the 3D space as the quantum channels,and one of the particles in the channels is used as the controlled particle.Analysis shows that when the quantum channels are of maximal entanglement,namely the channels are composed of a 3D Bell state and a 3D GHZ state,the total success probability of the controlled teleportation can reach 1.And this scheme can be expanded to control the teleportation of an unknown D-dimensional two-particle state.     

A method to restrain the charging effect on an insulating substrate in high energy electron beam lithography

Pattern distortions caused by the charging effect should be reduced while using the electron beam lithography process on an insulating substrate. We have developed a novel process by using the SX AR-PC 5000/90.1solution as a spin-coated conductive layer, to help to fabricate nanoscale patterns of poly-methyl-methacrylate polymer resist on glass for phased array device application. This method can restrain the influence of the charging effect on the insulating substrate effectively. Experimental results show that the novel process can solve the problems of the distortion of resist patterns and electron beam main field stitching error, thus ensuring the accuracy of the stitching and overlay of the electron beam lithography system. The main characteristic of the novel process is that it is compatible to the multi-layer semiconductor process inside a clean room, and is a green process, quite simple, fast, and low cost. It can also provide a broad scope in the device development on insulating the substrate,such as high density biochips, flexible electronics and liquid crystal display screens.     

Optical study of charge state of nitrogen-vacancy center in diamond

正The conversion between two nitrogen vacancy(NV)center charge states(NV°and NV~-)with laser in the range from 378 to 492 nm was experimentally studied and manipulated.With laser pump,NV~-(NV°)can be converted to NV°(NV~-)with the electron ionization(recharge)process.The wavelength and power dependent charge state conversion was proved to be single-photon process at short wavelength,while it is two-photon process at long wavelength.Also,the presence of metastable state in NV~-significantly affected the conversion process,which can be used to increase NV~-population from 72.5%to 80.5%by applying a magnetic field under 532 nm excitation.By involving the conversion between the two charge states,photon correlation measurement of single NV showed different behaviors,which was experimentally demonstrated to present the dynamics of three-partite coupling.Moreover,based on the charge state conversion,super-resolution optical image can be realized to detect NVs with the resolution down to 50 nm.The study of charge state conversion can be used for improving the fidelity of charge state polarization and subsequently optimizing the quantum control with NV center and resolution in the magnetometric and biological sensoring.     

Effect of a magnetic field on the energy levels of donor impurities in the ZnO parabolic quantum well

Energy levels of a donor impurity in the ZnO parabolic quantum well under the magnetic field are investigated using the variational method.The binding energy of the ground state,the energies of 2p±state and 1 s→2p±transition energies of a hydrogenic donor in the ZnO parabolic quantum well are numerically calculated as a function of the strength of magnetic field for different parabolic potential fields.The results show that the external magnetic field has an obvious influence on the binding energies and the 1 s→2p±transition energies of a hydrogenic donor.The Is to 2p±transition energy increases linearly with the strength of magnetic field,but the Is to 2p_ transition energy decreases when the strength of magnetic field increases for the small field strength. Compared to the GaAs parabolic well,the donors are more tightly bound to the ZnO parabolic well and the influence of external magnetic field on the binding energy of a donor is much stronger in the ZnO parabolic well.     

A Coding and Automatic Error-Correction Circuit Based on the Five-Particle Entangled State

In this paper, we discuss the concepts of quantum coding and error correction for a five-particle entangled state. Error correction can correct bit-reverse or phase-flip errors of one and two quantum states and is no longer limited to only one quantum state. We encode a single quantum state into a five-particle entangled state before being transferred to the sender. We designed an automatic error-correction circuit to correct errors caused by noise. We also simplify the design process for a multiple quantum error-correction circuit. We compare error-correction schemes for five and three entangled particles in terms of efficiency and capabilities. The results show that error-correction efficiency and fidelity are im- proved.     

CALCULATION FOR GEOMETRICAL ABERRATIONS OF A DEFLECTION SYSTEM WITH A UNIFORM ELECTROSTATIC FIELD

In this paper,formulas of third geometrical deflection aberrations for an ideal uniform electrostaticfield are derived by solving the motion equations of an electron passing through this field.The results can beused not only to estimate the distortion,astigamatism and field curvature,and coma produced by a Gaussianor shaped electron beam,but also to set the original size of the deflector and determine the effect caused bythe misalignment between the electron beam and the deflector.Some mistakes in Sturrock's paper(1955)arealso pointed out.     

CuO纳米线阵列的制备与特性

CuO nanowire arrays were prepared by oxidation of copper nanowires embedded in anodic aluminum oxide （AAO） membranes. The AAO was fabricated in an oxalic acid at a constant voltage. Copper nanowires were formed in the nanopores of the AAO membranes in an electrochemical deposition process. The oxidized copper nanowires at different temperatures were studied. X-ray diffraction patterns confirmed the formation of a CuO phase after calcining at 500 ？C in air for 30 h. A transmission electron microscopy was used to characterize the nanowire morphologies. Raman spectra were performed to study the CuO nanowire arrays. After measuring, we found that the current–voltage curve of the CuO nanowires is nonlinear.     

Fuzzy working state evaluating function and its algorithm for analogue circuits

The working state(WS) evaluation is a valuable task in the process of failure diagnosis in the analogue circuits. A fuzzy evaluating algorithm was proposed to quantify the working condition of analogue circuit regarded as fuzzy system. Several familiar WS evaluating functions based on fuzzy membership functions were also proposed to calculate the local working state indexes(WSI) of each node in an analogue circuit. The decision function combined with the WS evaluating functions is used to synthesize all the local WSI to the global WSI of the whole circuit. An example was presented to verify that the working status of the analogue circuits can be described by the new WS evaluating algorithm and the global WSI objectively and accurately.     

磁场作用下的一个含类氢施主杂质二维量子环中的电子能态

Using the finite element method, we investigate the lowest and first few excited state energies in a twodimensional GaAs quantum ring(QR) with a hydrogenic donor impurity and effective mass approximation under a uniform magnetic field perpendicular to the ring plane. We study in detail the dependence of the energy spectrum with different angular momentum on the inner radius, the outer radius and width of the QR, the magnetic field and impurity position. The results reveal that the electron energies increase with the inner radius while decrease with the outer radius and width of the QR; for a fixed ring, the magnetic field induces the increase of the electron energies. Moreover, the existence of impurity reduces energy levels, and the energy levels depend highly on the impurity position, which decreases as the impurity is far away from the center of the QR. Also, the dependence of the angular momentum on the energy spectrum is analyzed in detail.     

An Ultra Low Steady-State Current Power-on-Reset Circuit in 65nm CMOS Technology

A novel Power-on-reset （POR） circuit is proposed with ultra-low steady-state current consumption. A band=gap voltage eomparator is used to generate a stable pull-up voltage. To eliminate the large current consumptions of the analog part, a power switch is adopted to cut the supply of band-gap voltage comparator, which gained ultra-low current consumption in steady-state after the POR rest process completed. The state of POR circuit is maintained through a state latch circuit. The whole cir- cuit was designed and implemented in 65rim C1V[OS tech- nology with an active area of 120ttm＊160~m. Experimental results show that it has a steady pull=up voltage of 0.69V and a brown-out voltage of 0.49V under a 1.2V supply voltage rising from 0V, plus its steady-state current is only 9hA. The proposed circuit is suitable to be integrated in system on chip to provide a reliable POR signal.     

Effective mass of the ground state of the strong-coupling exciton in a quantum well

The properties of the effective mass of the ground state of the exciton, for which the electron (hole) is strongly coupled with interface-optical (IO) phonons but weakly coupled with bulk-longitudinal-optical (LO) phonons in a quantum well, are studied by means of Tokuda’s improved linear combination operator and a modified second Lee-Low-Pines transformation method. The results indicate that the contributions of the interaction between the electron (hole) and the different phonon branches to the effective ...     

The effect of electron cyclotron resonance plasma parameters on the aspect ratio of trenches in HgCdTe

Values of the aspect ratio for trenches etched into HgCdTe by an electron cyclotron resonance (ECR) plasma containing hydrogen and argon are limited by the phenomenon of etch lag. Modeling this plasma as an ion assisted, reactive-etching process leads to a set of conditions that greatly reduces etch lag. Use of these new process conditions produces trenches with aspect ratios greater than 3, widths less than 3 μm, and depths in excess of 15 μm.     

Experimental and theoretical research of electron emission mechanism of M-type cathodes

With the most advanced Synchronous Radiation Photoelectron Spectrum （SRPS）, the emission mechanism of M-type cathodes has been investigated from the perspective of chemical state. Based on the experimental results of SRPS analysis, a new model of the electron emission mechanism for M-type cathode is discussed. The main topics in this paper include the research status of electron emission mechanism of M-type cathodes; the advantages of SRPS technology; the distribution of oxygen chemical state on the cathode surface and the evolvement of oxygen chemical state during activation process; the relation between barium chemical state and osmium （Os）-coating; surplus barium and its formula; the characteristics of Os, and other noble metal coatings; the relation between film characteristics and emission performance of cathodes, the inhibition effects to the emission for Platinum （Pt）-coated cathode, etc. At the end of this paper, electron emission mechanism of M-type cathode is summarized and foreseen.     

Electron beam-induced current investigation of GaN Schottky diode

In this article, we report the electron beam-induced current (EBIC) measurements in a GaN Schottky diode performed in the line-scan configuration. A theoretical model with an extended generation source was used to accurately extract some minority carrier transport properties of the unintentionally doped n-GaN layer. The minority hole diffusion length is found to increase from ∼0.35 μm near the junction to ∼1.74 μm at the bulk regions. This change is attributed to an increase of the carrier lifetime caused by the polarization effects, which are preponderant in this component. For depth distances exceeding 0.65 μm, it is shown that the measured current is produced by the reabsorption recombination radiation process. This corresponds to an absorption coefficient of 0.178 μm⁻¹, in good agreement with the optical absorption measurement.     

A double-stage start-up structure to limit the inrush current used in current mode charge pump

A double-stage start-up structure to limit the inrush current used in current-mode charge pump with wide input range, fixed output and multimode operation is presented in this paper. As a widely utilized power source implement, a Li-battery is always used as the power supply for chips. Due to the internal resistance, a potential drop will be generated at the input terminal of the chip with an input current. A false shut down with a low supply voltage will happen if the input current is too large, leading to the degradation of the Li-battery''s service life. To solve this problem, the inrush current is limited by introducing a new start-up state. All of the circuits have been implemented with the NUVOTON 0.6 μm CMOS process. The measurement results show that the inrush current can be limited below 1 A within all input supply ranges, and the power efficiency is higher than the conventional structure.