Array-enhanced logical stochastic resonance subject to colored noise

This paper proposes an approach that uses a parallel array to improve the reliability and robustness of logical stochastic resonance subject to colored noise. The experimental results demonstrate that (i) the increase of array size can extend the optimal range of noise intensity and increase the maximum probability of obtaining correct logic operation. (ii) The optimal range of noise correlation time is broadened with the increase of array size. (iii) The main difference between logical stochastic resonance subject to white noise and colored noise is that the increase of noise correlation time broadens the optimal range of noise intensity when the stochastic noise is colored noise. At the same time, the maximum probability of obtaining correct logic operation is close to 1. Therefore, reliable and robust logic gate can be realized under a certain array size.     

SiGe optoelectronic metal-oxide semiconductor field-effect transistor

We propose a novel semiconductor optoelectronic switch that is a fusion of a Ge optical detector and a Si metal-oxide semiconductor field-effect transistor (MOSFET). The device operation is investigated with simulations and experiments. The switch can be fabricated at the nanoscale with extremely low capacitance. This device operates in telecommunication standard wavelengths, hence providing the surrounding Si circuitry with noise immunity from signaling. The Ge gate absorbs light, and the gate photocurrent is amplified at the drain terminal. Experimental current gain of up to 1000x is demonstrated. The device exhibits increased responsivity (approximately 3.5x) and lower off-state current (approximately 4x) compared with traditional detector schemes.     

Operational improvement of AlGaN/GaN HEMT on SiC substrate with the amended depletion region

In this paper, a high performance AlGaN/GaN High Electron Mobility Transistor (HEMT) on SiC substrates is presented to improve the electrical operation with the amended depletion region using a multiple recessed gate (MRG–HEMT). The basic idea is to change the gate depletion region and a better distribution of the electric field in the channel and improve the device breakdown voltage. The proposed gate consists of lower and upper gate to control the channel thickness. Also, the charge of the depletion region will change due to the optimized gate. In addition, a metal between the gate and drain including the horizontal and vertical parts is used to better control the thickness of the channel. The breakdown voltage, maximum output power density, cut-off frequency, maximum oscillation frequency, minimum noise figure, maximum available gain (MAG), and maximum stable gain (MSG) are some parameters for designers which are considered and are improved in this paper.     

部分耗尽结构绝缘体上硅器件的低频噪声特性

针对部分耗尽结构绝缘体上硅(silicon-on-insulator, SOI)器件低频噪声特性展开实验与理论研究. 实验结果表明, 器件低频噪声主要来源于SiO₂-Si界面附近缺陷态对载流子的俘获与释放过程; 基于此理论可提取前栅和背栅氧化层界面附近缺陷态密度分别为8×10¹⁷ eV^-1·cm^-3和2.76×10¹⁷ eV^-1·cm^-3. 基于电荷隧穿机理, 在考虑隧穿削弱因子、隧穿距离与时间常数之间关系的基础上, 提取了前、背栅氧化层内缺陷态密度随空间的分布情况. 此外, SOI器件沟道电流归一化噪声功率谱密度随沟道长度的增加而线性减小, 这表明器件低频噪声主要来源于沟道的闪烁噪声. 最后, 基于电荷耦合效应, 分析了背栅电压对前栅阈值电压、沟道电流以及沟道电流噪声功率谱密度的影响.     

Time-varying coupling-induced logical stochastic resonance in a periodically driven coupled bistable system

Coupling-induced logical stochastic resonance(LSR) can be observed in a noise-driven coupled bistable system where the behaviors of system can be interpreted consistently as a specific logic gate in an appropriate noise level. Here constant coupling is extended to time-varying coupling, and then we investigate the effect of time-varying coupling on LSR in a periodically driven coupled bistable system. When coupling intensity oscillates periodically with the same frequency with periodic force or relatively high frequency, the system successfully yields the desired logic output. When coupling intensity oscillates irregularly with phase disturbance, large phase disturbance reduces the area of optimal parameter region of coupling intensity and response speed of logic devices. Although the system behaves as a desired logic gate when the frequency of time-periodic coupling intensity is precisely equal to that of periodic force, the desired logic gate is not robust against tiny frequency difference and phase disturbance. Therefore, periodic coupling intensity with high frequency ratio is an optimal option to obtain a reliable and robust logic operation.     

强反型区下纳米MOSFET的射频噪声机理分析

为了有效地表征纳米MOSFET强反型区下的射频噪声特性,研究了其噪声建模的方法。在分析45 nm MOSFET射频小信号等效电路参数提取结果的基础上,建立了该器件漏极电流噪声的简洁模型。该模型完整地表征了决定45 nm器件噪声机理的三个组成部分:本征漏极电流噪声、栅极管脚寄生电阻热噪声和栅漏衬底寄生电磁耦合噪声。噪声测量在验证所建模型准确性和精度的同时,还表明:45 nm MOSFET的本征漏极电流噪声为受抑制的散粒噪声,并且随着栅源偏压的降低受抑制性逐渐减弱直至消失。     

GaN HEMT栅边缘电容用于缺陷的研究

本文对GaN HEMT栅漏电容的频率色散特性进行分析,认为栅边缘电容的色散是导致栅漏电容频率色散特性不同于圆肖特基二极管电容的主要原因. 通过对不同栅偏置条件下缺陷附加电容与频率关系的拟合,发现小栅压下的缺陷附加电容仅满足单能级缺陷模型,而强反向栅压下的缺陷附加电容同时满足单能级和连续能级缺陷模型. 实验中栅边缘电容的频率色散现象在钝化工艺后出现,其反映的缺陷很可能是钝化工艺引入,且位于源漏间栅金属未覆盖区域的表面. 最后通过低频噪声技术进一步验证栅边缘电容提取缺陷参数的可行性. 低频噪声技术获得的单能级 关键词： HEMT 边缘电容 缺陷 低频噪声     

Quantum processing photonic states in optical lattices

The mapping of photonic states to collective excitations of atomic ensembles is a powerful tool which finds a useful application in the realization of quantum memories and quantum repeaters. In this work we show that cold atoms in optical lattices can be used to perform an entangling unitary operation on the transferred atomic excitations. After the release of the quantum atomic state, our protocol results in a deterministic two qubit gate for photons. The proposed scheme is feasible with current experimental techniques and robust against the dominant sources of noise.     

光纤克尔门全光再生器特性分析

讨论了光纤克尔门再生器抑制输入光脉冲的加性噪声和脉冲中心抖动的机制，分析了再生器中各元件的配置对其抑制噪声能力的影响。指出根据通信线路中心的噪声特性，适当选择克尔门中色散位移光纤长度，可以大大抑制通信系统中的噪声，提高系统通信容量。     

Minimum construction of two-qubit quantum operations

Optimal construction of quantum operations is a fundamental problem in the realization of quantum computation. We here introduce a newly discovered quantum gate, B, that can implement any arbitrary two-qubit quantum operation with minimal number of both two- and single-qubit gates. We show this by giving an analytic circuit that implements a generic nonlocal two-qubit operation from just two applications of the B gate. Realization of the B gate is illustrated with an example of charge-coupled superconducting qubits for which the B gate is seen to be generated in shorter time than the CNOT gate.     

Observation of nonconservation characteristics of radio frequency noise mechanism of 40-nm n-MOSFET

Bias non-conservation characteristics of radio-frequency noise mechanism of 40-nm n-MOSFET are observed by modeling and measuring its drain current noise. A compact model for the drain current noise of 40-nm MOSFET is proposed through the noise analysis. This model fully describes three kinds of main physical sources that determine the noise mechanism of 40-nm MOSFET, i.e., intrinsic drain current noise, thermal noise induced by the gate parasitic resistance, and coupling thermal noise induced by substrate parasitic effect. The accuracy of the proposed model is verified by noise measurements, and the intrinsic drain current noise is proved to be the suppressed shot noise, and with the decrease of the gate voltage, the suppressed degree gradually decreases until it vanishes. The most important findings of the bias non-conservative nature of noise mechanism of 40-nm n-MOSFET are as follows.(i) In the strong inversion region, the suppressed shot noise is weakly affected by the thermal noise of gate parasitic resistance. Therefore, one can empirically model the channel excess noise as being like the suppressed shot noise.(ii) In the middle inversion region, it is almost full of shot noise.(iii) In the weak inversion region, the thermal noise is strongly frequency-dependent, which is almost controlled by the capacitive coupling of substrate parasitic resistance. Measurement results over a wide temperature range demonstrate that the thermal noise of 40-nm n-MOSFET exists in a region from the weak to strong inversion, contrary to the predictions of suppressed shot noise model only suitable for the strong inversion and middle inversion region. These new findings of the noise mechanism of 40-nm n-MOSFET are very beneficial for its applications in ultra low-voltage and low-power RF, such as novel device electronic structure optimization, integrated circuit design and process technology evaluation.     

Modulation bandwidth and noise limit of photoconductive gates

The modulation bandwidth and noise limit of a photoconductive sampling gate are studied by reducing the parasitic capacitance and leakage current of the sampling circuit using an integrated junction field-effect transistor (JFET) source follower. The modulation bandwidth of the photoconductive sampling gate is limited by the external parasitic capacitance, and its efficiency is found to saturate at a laser gating power of about 1 mW. It is determined that the noise of the photoconductive sampling gate is dominated by the photovoltaic current due to the gating laser amplitude fluctuation. A minimum noise level of 4 nV Hz^–1/2 has been measured, and an enhancement in signal-to-noise ratio by a factor of >45 has been achieved after the integration of the source follower with the photoconductive sampling gate. The JFET source follower serves to increase the modulation bandwidth of the photoconductive sampling gate by about 15 times and buffer the charge of the measured signal using its extremely high gate input impedance. The performance of the photoconductive sampling gate in regard to invasiveness and gating efficiency has been optimized, while a picosecond temporal resolution has been maintained and the signal-to-noise performance has been enhanced using a gating laser power as low as 10 W.     

Shot noise in the current of a surface acoustic-wave-driven single-electron pump

We have measured the noise at approximately 1.6 MHz in the current produced by a single-electron pump that uses an approximately 2.7 GHz surface acoustic wave (SAW). The current can be varied by altering the voltage applied to surface gates. Over the range of gate voltage where the current is close to the quantized value corresponding to one electron being transported per cycle of the SAW, the noise in the current is dominated by shot noise, whereas away from this range the noise mostly arises from switching the charge states of electron traps in the material. By combining measurements of the shot noise and the current, we determined how the error rates--the probabilities of transporting zero or two electrons in a cycle--vary with gate voltage when the current is close to the quantized value. The results obtained suggest that these two probabilities are controlled by closely linked mechanisms.     

基于Gm-APD的成像激光雷达目标探测特性

针对采用盖革模式雪崩光电二极管（Gm-APD）作为探测器的成像激光雷达,介绍了其测距原理及3D成像原理,并对如何提高其探测性能的方法进行了分析。以分析Gm-APD触发信号的统计特性为基础,对出现在距离门内不同位置目标的探测概率和虚警概率进行了研究与仿真,结果表明,目标处在距离门最前面时,探测概率受噪声水平影响最小,虚警概率受信号强度影响最大;目标靠近距离门中间位置时,探测概率随噪声水平增大下降缓慢,虚警概率随信号强度增大下降缓慢;目标处在距离门末尾时探测概率受噪声水平影响最大,而虚警概率几乎与回波信号强度无关。     

Coulomb blockade of a noisy metallic box: a realization of Bose-Fermi Kondo models

We focus on a metallic quantum dot coupled to a reservoir of electrons through a single-mode point contact and capacitively connected to a back gate, by including that the gate voltage can exhibit noise; this will occur when connecting the gate lead to a transmission line with a finite impedance. The voltage fluctuations at the back gate can be described through a Caldeira-Leggett model of harmonic oscillators. For weak tunneling between the lead and the dot, exploiting the anisotropic Bose-Fermi spin model, we show that zero-point fluctuations of the environment can markedly alter the Matveev Kondo fixed point leading to an amplification of the charge quantization phenomenon.     

Non-Geometric Conditional Phase Gate by Quantum Zeno Dynamics in Laser-Excited Nitrogen-Vacancy Centers

Based on the quantum Zeno dynamics,we propose a two-qubit non-geometric conditional phase gate between two nitrogen-vacancy centers coupled to a whispering-gallery mode cavity.The varying phases design of periodic laser can be used for realizing non-geometric conditional phase gate,and the cavity mode is virtually excited during the gate operation.Thus,the fidelity of the gate operation is insensitive to cavity decay and the fluctuation of the preset laser intensity.The numerical simulation with a realistic set of experimental parameters shows that the gate fidelity 0.987 can be within reached in the near future.     

AC shot noise through a vibrating quantum dot

In this paper we investigate the joint effects of the electron-phonon interaction and an external alternating (ac) gate voltage on the spectral density of shot noise through a vibrating quantum dot system, by applying the Lang-Firsov canonical transformation and the Keldysh nonequilibrium Green's function (NGF) technique. We find that the effects of the electron-phonon and electron-photon interaction on the differential shot noise are different. The main resonant peak of the differential shot noise is decreased only when a time-dependent gate voltage is imposed on quantum dot. With the ac field amplitude increasing, the main resonant peak of the differential shot noise decreases. The Fano factor of the system, which exhibits the deviation of shot noise from the Schottky formula, is also studied. Super-Poissonian shot noise appears due to the photon absorption (emission) processes in the low bias voltage region.     

Information Complexity of Quantum Gates

This paper considers the realizability of quantum gates from the perspective of information complexity. Since the gate is a physical device that must be controlled classically, it is subject to random error. We define the complexity of gate operation in terms of the difference between the entropy of the variables associated with initial and final states of the computation. We argue that the gate operations are irreversible if there is a difference in the accuracy associated with input and output variables. It is shown that under some conditions the gate operation may be associated with unbounded entropy, implying impossibility of implementation. PACS number: 03.65     

Shot noise in a quantum dot coupled to carbon nanotube terminals applied with a microwave field

We have investigated the spectral density of shot noise for the system of a quantum dot (QD) coupled to two single-wall carbon nanotube terminals irradiated with a microwave field on the QD. The terminal features are involved in the shot noise through modifying the self-energy of QD. The contributions of carbon nanotube terminals to the shot noise exhibit obvious behaviors. The novel side peaks are associated with the photon absorption and emission procedure accompanying the suppression of shot noise. The shot noise in balanced absorption belongs to sub-Poissonian, and it is symmetric with respect to the gate voltage. The differential shot noise displays intimate relation with the nature of carbon nanotubes and the applied microwave field. It exhibits asymmetric behavior for the unbalanced absorption case versus gate voltage. The Fano factor of the system exhibits the deviation of shot noise from the Schottky formula, and the structures of terminals obviously contribute to it. The super-Poissonian and sub-Poissonian shot noise can be achieved in the unbalanced absorption in different regime of source-drain bias.     

基于TOAD的10Gb/s全光或门

基于太赫兹光非对称解复用器（TOAD），提出了一种全光或门的实现方案.从TOAD原理出发，从理论上证实了该方案实现全光或运算的可行性.在此基础上进行了实验研究，成功实现了10 Gb/s的全光或运算.实验采用1100和0110编码的两路数据信号，完全验证了或运算真值表中各种可能的情况，并显示出该方案对实现任意编码或伪随机码数据或运算的潜力.对SOA增益恢复时间对结果的影响提出了改进办法.最后分析表明,该方案具有实现超高速高消光比或运算的潜力.