"量身定做"单光子波包:在量子网络中控制光子/自旋量子界面

文章简要地介绍了如何在量子网络中控制量子界面动力学以实现静态量子比特和动态量子比特的相互转换．具体言之，该界面由半导体量子点、固体光学微腔以及光学波导管构成，静态及动态比特分别为量子点中的电子自旋和波导管中的单光子波包所携带．界面动力学的控制则是基于对量子点、微腔和波导管耦合系统的量子电动力学的严格求解．据此可实现网络中两个远距离节点间的量子态传输、交换以及确定性的建立量子纠缠等量子操作．上述量子界面亦可用于任意指定波形的单光子源或者单光子探测装置。     

Giant Spin Transfer Torque in Atomically Thin Magnetic Bilayers

In cavity quantum electrodynamics,the multiple reflections of a photon between two mirrors defining a cavity is exploited to enhance the light-coupling of an intra-cavity atom.We show that this paradigm for enhancing the interaction of a flying particle with a localized object can be generalized to spintronics based on van der Waals 2D magnets.Upon tunneling through a magnetic bilayer,we find that the spin transfer torques per electron incidence can become orders of magnitude larger than ?/2,mad...     

Timing synchronization algorithm based on FH sequen- ce for coherent optical OFDM systems with carrier freq- uency offset

A novel symbol timing synchronization algorithm based on Frank-Hermiller (FH) sequence is proposed for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systemswith carrier frequency offset. The timing synchronization is realized by using only one training symbol which is composed of conjugated symmetric sequences. The timing estimation of the proposed algorithm is robust to poor frequency offset. The proposed algorithm is shown to eliminate the timing sidelobes of Park’s algorithm and has a more accurate timing estimation. In the condition of frequency offset, the timing metric of the proposed method still maintains its peak value at the correct timing point, while the values are almost zero at all other positions.     

范德瓦耳斯体系中的量子层电子学

范德瓦耳斯体系中层间耦合的存在使电子波函数扩展分布在各层上,使得空间离散的层自由度成为量子力学自由度.层自由度与电子质心自由度的耦合塑造了动量空间中非平庸的层赝自旋结构,导致丰富的量子几何性质.这些性质为晶格失配的范德瓦耳斯体系所独有,引起各种新颖的输运和光学效应,线性和非线性响应,并为多种器件应用提供新思路,成为量子层电子学研究的前沿课题.本文简要评述了这一范德瓦耳斯材料体系中的新兴研究方向,并结合量子层电子学与非线性电子学、转角电子学、手征电子学等新领域的交叉,对未来一段时间的发展进行展望.     

基于NetMagic的城域网流量仿真研究

网络流量特性研究对网络性能管理、QoS等具有重要意义。针对目前对网络性能测试和性能评估的需要,设计了一种基于NetMagic的城域网流量仿真和分析方案。首先对NetMagic平台进行了概要介绍,然后提出了Poisson-Gamma的城域网流量模型,最后依据该模型使用NetMagic生成仿真流量,并对仿真流量的时域、概率密度分布与真实网络流量的统计结果进行比对,证明了该模型能够较为真实地反映城域网的网络流量特性。     

一种用于3.1–4.8GHz MB-OFDM 超宽带系统的CMOS接收机

本文介绍一种应用于3.1-4.8GHz 多频带正交频分复用超宽带系统的全集成全差分CMOS接收机芯片。在接收机射频前端中应用了一种增益可变的低噪声放大器和合并结构的正交混频器。在I/Q中频通路中则集成了5阶Gm-C结构的有源低通滤波器以及可变增益放大器。芯片通过Jazz 0.18μm RF CMOS工艺流片,含ESD保护电路。该接收机最大电压增益为65dB,增益可调范围为45dB,步长6dB;接收机在3个频段的平均噪声系数为6.4-8.8dB,带内输入三阶交调量(IIP3)为-5.1dBm。芯片面积为2.3平方毫米,在1.8V电压下,包括测试缓冲电路和数字模块在内的总电流为110mA。     

“量身定做”单光子波包：在量子网络中控制光子/自旋量子界面

文章简要地介绍了如何在量子网络中控制量子界面动力学以实现静态量子比特和动态量子比特的相互转换. 具体言之,该界面由半导体量子点、固体光学微腔以及光学波导管构成, 静态及动态比特分别为量子点中的电子自旋和波导管中的单光子波包所携带. 界面动力学的控制则是基于对量子点、微腔和波导管耦合系统的量子电动力学的严格求解. 据此可实现网络中两个远距离节点间的量子态传输、交换以及确定性的建立量子纠缠等量子操作. 上述量子界面亦可用于任意指定波形的单光子源或者单光子探测装置.     

A 3.1-4.8 GHz CMOS receiver for MB-OFDM UWB

An integrated fully differential ultra-wideband CMOS receiver for 3.1-4.8 GHz MB-OFDM systems is presented. A gain controllable low noise amplifier and a merged quadrature mixer are integrated as the RF front-end. Five order Gm-C type low pass filters and VGAs are also integrated for both I and Q IF paths in the receiver. The ESD protected chip is fabricated in a Jazz 0.18μm RF CMOS process and achieves a maximum total voltage gain of 65 dB, an AGC range of 45 dB with about 6 dB/step, an averaged total noise figure of 6.4 to 8.8 dB over 3 bands and an in-band IIP3 of-5.1 dBm. The receiver occupies 2.3 mm2 and consumes 110 mA from a 1.8 V supply including test buffers and a digital module.     

OFDM超宽带3.1-4.8GHz CMOS射频收发机设计

本文介绍一种应用于3.1-4.8GHz 多频带正交频分复用超宽带系统的CMOS射频收发机芯片的设计和实现。射频收发机采用零中频结构,主要模块包括：增益可控的宽带低噪声放大器、正交跨导复用下变频混频器、5阶Gm-C切比雪夫低通滤波器及可变增益放大器;采用多项滤波器进行边带杂散抑制的快速跳变频率综合器;宽带线性上变频正交调制器、片内有源双转单电路及输出可变增益放大器。芯片测试结果表明,接收机最大能够获得68dB的电压增益,其中42dB为可变增益,增益步长为6dB;在三个子带内的噪声系数为5.5~8.8dB;带内IIP3和带外IIP3不低于-4dBm和9dBm;发射机能够提供-10.7~-3dBm的输出功率,7.7dB的增益可控;输出1dB压缩点不低于-7.7dBm;发射信号边带抑制为32.4dBc,载波泄漏抑制可达31.1dBc;频率综合器的快速跳边时间低于2.05nS。芯片采用Jazz 0.18μm射频CMOS工艺流片,包括ESD防护PAD在内芯片总面积为6.1mm2;在1.8V的电源电压下,整个芯片的工作电流为221mA (RX+TX+SYN+Buffers）。     

A novel timing synchronization for CO-OFDM systems using CAZAC sequences

A novel symbol timing synchronization algorithm based on constant amplitude zero auto correlation (CAZAC) sequences is proposed for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. The training symbol of the proposed algorithm is comprised of four different parts, utilizing even symmetry property of each part to accomplish timing synchronization. The performance of the proposed algorithm is demonstrated by means of simulations in OFDM and CO-OFDM systems. The proposed algorithm is shown to eliminate the timing sidelobes of Park’s algorithm and has a more accurate timing estimation. In the condition of chromatic dispersion (CD), the timing metric of the proposed method still maintains its peak value at the correct timing point, while the values are almost 0 at all the other positions. Meanwhile, the timing mean square error (MSE) of the proposed algorithm remains around 10-6.