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A Quantum Network System of QSS-QDC Using χ-Type Entangled States
Chang Ho Hong,Jin O Heo,Jong in Lim,Hyung jin Yang,**
Chin. Phys. Lett. 2012, 29 (5):
050303
.
DOI: 10.1088/0256-307X/29/5/050303
A multiuser quantum direct communication network system for N users utilizing χ−type entangled states is proposed. The network system is composed of a communication center, N users, and N quantum lines linking the center and the N users. There is no quantum line among users, and therefore only N quantum lines are necessary for communication between users. Using one χ-type entangled state, in this protocol we are able to send two bits of information through direct communication and, at the same time, share two bits of quantum keys. The security of the protocol is then analyzed.
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Scale-Covariant Theory of Gravitation Through Self-Similarity
José Antonio Belinchón*
Chin. Phys. Lett. 2012, 29 (5):
050401
.
DOI: 10.1088/0256-307X/29/5/050401
We study the scale-covariant theory of gravitation proposed by Canuto under the self-similar hypothesis. By considering the matter collineation approach, we deduce the form of the main quantities and obtain some restrictions on the behavior of the gauge function, φ(t). We apply the obtained results to study the Bianchi I, VII0, IX and Kantowsky Sachs models, and arrive at the conclusion that instead of considering a varying G theory, the solution is only valid for a particular value of the parameter of the equation of state, γ,. This leads us to obtain φ(t) = const, and by taking into account the external condition, Gφ2 = const, we may arrive at the conclusion that G = const. Therefore, all the obtained solutions are the same as the ones obtained in the framework of general relativity.
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The Slow Dynamics of the Zero-Range Process in the Framework of the Traps Model
QI Kai,TANG Ming**,CUI Ai-Xiang,FU Yan
Chin. Phys. Lett. 2012, 29 (5):
050505
.
DOI: 10.1088/0256-307X/29/5/050505
The relaxation dynamics of the zero-range process (ZRP) has been an interesting problem. In this study, we set up the relationship between the ZRP and a model of traps, and investigate the slow dynamics of the ZRP in the framework of the trap model. Through statistical quantities such as the average rest time, the particle distribution, the two-time correlation function and the average escape time, we find that the particle interaction, especially the resulting condensation, can significantly influence the dynamics. In the stationary state, both the average rest time and the average escape time caused by the attraction among particles are obtained analytically. In the transient state, a hierarchical nature of the aging dynamics is revealed by both simulations and scaling analysis. Moreover, by comparing the particle diffusion in both the transient state and the stationary state, we find that the closer the ZRP systems approach the stationary state, the more slowly the particles diffuse.
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Stochastic Resonance-Like and Resonance Suppression-Like Phenomena in a Bistable System with Time Delay and Additive Noise
SHU Chang-Zheng,NIE Lin-Ru**,ZHOU Zhong-Rao
Chin. Phys. Lett. 2012, 29 (5):
050506
.
DOI: 10.1088/0256-307X/29/5/050506
Stochastic resonance (SR)-like and resonance suppression (RS)-like phenomena in a time-delayed bistable system driven by additive white noise are investigated by means of stochastic simulations of the power spectrum, the quality factor of the power spectrum, and the mean first-passage time (MFPT) of the system. The calculative results indicate that: (i) as the system is driven by a small periodic signal, the quality factor as a function delay time exhibits a maximal value at smaller noise intensities, i.e., an SR-like phenomenon. With the increment in additive noise intensity, the extremum gradually disappears and the quality factor decreases monotonously with delay time. (ii) As the additive noise intensity is smaller, the curve of the MFPT with respect to delay time displays a peak, i.e., an RS-like phenomenon. At higher levels of noise, however, the non-monotonic behavior is lost.
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High-Spin States in Transuranium Nuclei 242,244Pu
ZHAO Yue,KANG Xu-Zhong,SHEN Shui-Fa,**,YAN Yu-Peng,HE Chuang-Ye,YAN Shi-Wei
Chin. Phys. Lett. 2012, 29 (5):
052101
.
DOI: 10.1088/0256-307X/29/5/052101
We investigate the structure of yrast bands in the transuranium nuclei 242Pu and 244Pu in the framework of the projected shell model, which is a fully quantum mechanical and microscopic approach. It is found that an appropriate modification of the standard Nilsson spin−orbital parameters in the N=6 proton shell is necessary to correctly describe the high−spin backbending phenomenon in nucleus 244Pu. In order to test whether this modification is correct, the same modified parameters are used to calculate the yrast band of its neighboring isotope 242Pu. It is found that without this modification, a backbending will occur at spin I=20, which is not supported by the experimental data.
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Single- and Dual-Channel DPSK Signal Amplitude Regeneration Based on a Single Semiconductor Optical Amplifier
HUANG Xi,QIN Cui,YU Yu,ZHANG Zheng,ZHANG Xin-Liang**
Chin. Phys. Lett. 2012, 29 (5):
054202
.
DOI: 10.1088/0256-307X/29/5/054202
We experimentally demonstrate that, based on operational condition optimization, a common quantum well (QW) semiconductor optical amplifier (SOA) has the ability of amplitude regeneration for return-to-zero (RZ) differential phase shift keying (DPSK) signals. For a single-channel RZ-DPSK regeneration scheme, a significant eye-opening enhancement and a negative power penalty of about 1.0 dB are obtained. For dual-channel RZ-DPSK regeneration, it can also be found that the eye-opening improvement and power penalty decrease in each channel. In addition, the DPSK regeneration scheme based on a single QW SOA is quite simple and stable.
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Wave Optics in Discrete Excitable Media
GU Guo-Feng,WEI Hai-Ming,TANG Guo-Ning**
Chin. Phys. Lett. 2012, 29 (5):
054203
.
DOI: 10.1088/0256-307X/29/5/054203
Refraction and reflection of planar waves in a discrete excitable medium is numerically investigated by using the Greenberg–Hasting model. It is found that the medium is anisotropic because the speed of the planar wave depends on the excitability of the medium and the direction of wave propagation. The reflection, diffraction, refraction, double refraction and delayed refraction are observed by using the correct choice of model parameters. When the incident angle is larger than the critical angle, the reflection, which is a back refraction, takes place. The reflection angle changes with the incident angle. The refraction in certain situations obeys Snell's law. Also, our results demonstrate that the incident, refracted and reflected waves can have different periods. The reflected and refracted waves can disappear.
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Flat Supercontinuum Generation within the Telecommunication Wave Bands in a Photonic Crystal Fiber with Central Holes
HAN Ying,**,HOU Lan-Tian,ZHOU Gui-Yao,YUAN Jin-Hui,XIA Chang-Ming,WANG Wei,WANG Chao,HOU Zhi-Yun,
Chin. Phys. Lett. 2012, 29 (5):
054208
.
DOI: 10.1088/0256-307X/29/5/054208
Flat supercontinuum in the telecommunication wave bands of E+S+C is generated by coupling a train of femtosecond pulses generated by a mode-locked Ti:sapphire laser into the fundamental mode of a photonic crystal fiber with central holes fabricated in our lab. The pulse experiences the anomalous dispersion regime, and the soliton dynamic effect plays an important role in supercontinuum generation. The output spectrum in the wavelength range of 1360–1565 nm does not include significant ripples due to higher pump peak power, and the normalized intensity shows less fluctuation.
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Luminescence and Thermal Properties of Er:GSGG and Yb,Er:GSGG Laser Crystals
SUN Dun-Lu**,LUO Jian-Qiao,XIAO Jing-Zhong,ZHANG Qing-Li,CHEN Jia-Kang,LIU Wen-Peng,KANG Hong-Xiang,YIN Shao-Tang
Chin. Phys. Lett. 2012, 29 (5):
054209
.
DOI: 10.1088/0256-307X/29/5/054209
Er3+−doped and Yb3+/Er3+ co−doped Gd3Sc2Ga3O12 (abbreviated as Er:GSGG and Yb,Er:GSGG, respectively) laser crystals are investigated by using a combination of spectroscopic measurements and thermal characterizations. An absorption peak of Yb,Er:GSGG crystal shifts to 970 nm and its absorption band broadens obviously, which makes the crystal suitable for pumping by a 970 nm laser diode (LD). This crystal also exhibits a shorter lifetime of a lower laser level, a larger emission cross section and higher thermal conductivity than those of Er:GSGG. All these factors suggest that Yb3+/Er3+ co−doping has a positive effect on improving the spectroscopic and thermal performances in GSGG based laser crystals, and imply that double-doped Yb,Er:GSGG crystal is a potential candidate as an excellent LD pumped 2.79 µm laser material.
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Pulsed Chemical Oxygen Iodine Lasers Excited by Pulse Gas Discharge with the Assistance of Surface Sliding Discharge Pre-ionization
LI Guo-Fu,**,YU Hai-Jun,DUO Li-Ping,JIN Yu-Qi,WANG Jian,SANG Feng-Ting,WANG De-Zhen
Chin. Phys. Lett. 2012, 29 (5):
054212
.
DOI: 10.1088/0256-307X/29/5/054212
Continuous-wave chemical oxygen-iodine lasers (COILs) can be operated in a pulsed operation mode to obtain a higher peak power. The key point is to obtain a uniform and stable glow discharge in the mixture of singlet delta oxygen and iodide. We propose using an electrode system with the assistance of surface sliding pre-ionization to solve the problem of the stable glow discharge with a large aperture. The pre-ionization unit is symmetrically fixed on the plane of the cathode surface. A uniform and stable glow discharge is obtained in a mixture of iodide (such as CH3I) and nitrogen at the specific deposition energy of 4.5 J/L, pressure of 1.99–3.32 kPa, aperture size of 11 cm×10 cm. The electrode system is applied in a pulsed COIL. Laser energy up to 4.4 J is obtained and the specific energy output is 2 J/L.
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Self-Q-Switched and Mode-Locked Cr,Nd:YAG Laser under Direct 885 nm Diode Laser Pumping
JIANG Man,ZHANG Qiu-Lin,ZHOU Wen-Jia,ZHANG Jing,ZHANG Dong-Xiang,FENG Bao-Hua**
Chin. Phys. Lett. 2012, 29 (5):
054214
.
DOI: 10.1088/0256-307X/29/5/054214
A simultaneous self-Q-switched and mode-locked laser in a direct 885 nm diode-pumped Cr,Nd:YAG crystal is demonstrated. An improvement of the slope efficiency (38.1%) in the absorbed pump power is obtained under direct pumping. Under the maximum output power of 3.36 W, the repetition rate of the Q-switched envelopes is 95 kHz and the corresponding pulse width is 400 ns. Almost 100% mode-locked modulation depth is observed at the output power of 75 mW. The repetition rate of mode-locked pulses within a Q-switched envelope is 130 MHz, and the mode-locked pulse width stays within the scale of 500 ps.
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Performance Comparison of Mode-Locked Erbium-Doped Fiber Laser with Nonlinear Polarization Rotation and Saturable Absorber Approaches
M. A. Ismail,S. J. Tan,N. S. Shahabuddin,S. W. Harun,**,H. Arof,H. Ahmad
Chin. Phys. Lett. 2012, 29 (5):
054216
.
DOI: 10.1088/0256-307X/29/5/054216
A mode-locked erbium-doped fiber laser (EDFL) is demonstrated using a highly concentrated erbium-doped fiber (EDF) as the gain medium in a ring configuration with and without a saturable absorber (SA). Without the SA, the proposed laser generates soliton pulses with a repetition rate of 12 MHz, pulse width of 1.11 ps and energy pulse of 1.6 pJ. By incorporating SA in the ring cavity, the optical output of the laser changes from soliton to stretched pulses due to the slight change in the group velocity dispersion. With the SA, a cleaner pulse is obtained with a repetition rate of 11.3 MHz, a pulse width of 0.58 ps and a pulse energy of 2.3 pJ.
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Correlation between Temperature and Velocity Fluctuations in the Near-Wall Region of Rotating Turbulent Channel Flow
YANG Zi-Xuan,CUI Gui-Xiang**,XU Chun-Xiao,ZHANG Zhao-Shun,SHAO Liang
Chin. Phys. Lett. 2012, 29 (5):
054702
.
DOI: 10.1088/0256-307X/29/5/054702
The correlation between the temperature and streamwise velocity fluctuations in rotating turbulent channel flow is investigated. Unlike the previously found analogous property between the statistics of the temperature and streamwise velocity fluctuations, the correlation can more appropriately reveal the similarity between two random processes. The analysis of the correlation coefficient obtained from the database of direct numerical simulation indicates that the rotation weakens the correlation in most regions of the flow, especially on the suction side. Nevertheless, the correlation is slightly enhanced by the rotation in some regions of the rotating channel, which challenges the general understanding that rotation undoubtedly weakens the correlation. To discuss the mechanism of the rotating effect on the correlation, the transport equations of the variance of temperature and streamwise velocity fluctuations are considered. The Coriolis force is found to have an indirect effect on the correlation.
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In-Situ SRPES Study on the Band Alignment of (0001)CdS/CdTe Heterojunction
GAO Jun-Ning,JIE Wan-Qi**,YUAN Yan-Yan,ZHA Gang-Qiang,XU Ling-Yan,WU Heng,WANG Ya-Bin,YU Hui,ZHU Jun-Fa
Chin. Phys. Lett. 2012, 29 (5):
057301
.
DOI: 10.1088/0256-307X/29/5/057301
The band alignment of a (0001)CdS/CdTe heterojunction is in situ studied by synchrotron radiation photoemission spectroscopy (SRPES). The heterojunction is formed through stepwise deposition of a CdTe film on a wurtzite (0001)CdS single crystalline substrate via molecular beam epitaxy. CdS shows an upward band bending of 0.55 eV, the valence band offset ΔEV is calculated to be 0.65 eV and the conduction band offset ΔEC is 0.31 eV. The interfacial band alignment is sketched to display type-I band alignment.
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Chemical Vapour Deposition Graphene Radio-Frequency Field-Effect Transistors
MA Peng,JIN Zhi**,GUO Jian-Nan,PAN Hong-Liang,LIU Xin-Yu,YE Tian-Chun,WANG Hong,WANG Guan-Zhong
Chin. Phys. Lett. 2012, 29 (5):
057302
.
DOI: 10.1088/0256-307X/29/5/057302
We report the dc and rf performance of graphene rf field-effect transistors, where the graphene films are grown on copper by using the chemical vapour deposition (CVD) method and transferred to SiO2/Si substrates. Composite materials, benzocyclobutene and atomic layer deposition Al2O3 are used as the gate dielectrics. The observation of n− and p-type transitions verifies the ambipolar characteristics in the graphene layers. While the intrinsic carrier mobility of CVD graphene is extracted to be 1200 cm2/V⋅s, the parasitic series resistances are demonstrated to have a serious impact on device performance. With a gate length of 1 µm and an extrinsic transconductance of 72 mS/mm, a cutoff frequency of 6.6 GHz and a maximum oscillation frequency of 8.8 GHz are measured for the transistors, illustrating the potential of the CVD graphene for rf applications.
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Electrical Properties of Lead Zirconate Titanate Thick Film Containing Micro- and Nano-Crystalline Particles
LU Ran,JIANG Gen-Shan,LI Bin,ZHAO Quan-Liang,ZHANG De-Qing,YUAN Jie,CAO Mao-Sheng**
Chin. Phys. Lett. 2012, 29 (5):
058101
.
DOI: 10.1088/0256-307X/29/5/058101
We report the ferroelectric, dielectric and piezoelectric properties of a dense and crack-free lead zirconate titanate (Pb(Zr0.52Ti0.48)O3, PZT) thick film containing micro− and nano-crystalline particles. The results show that these electrical properties are dependent strongly on the annealing temperature and film thickness. For the different-annealing-temperature and different-thickness films, the higher-annealing-temperature thicker ones show the larger remnant polarization and smaller coercive field. The dielectric results show that relative dielectric constant achieves the largest value at annealing temperature of 700°C, and increases with the increasing film thickness. For the piezoelectric properties, the longitudinal piezoelectric coefficient increases linearly with the film thickness increasing and the 4−µm -thick PZT film shows the largest value of about 200.65 pC/N. Therefore, the PZT thick films present good electric properties and enlarged potential in MEMS applications.
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The Leakage Current Improvement of a Ni-Silicided SiGe/Si Junction Using a Si Cap Layer and the PAI Technique
CHANG Jian-Guang,WU Chun-Bo,JI Xiao-Li**,MA Hao-Wen,YAN Feng,SHI Yi,ZHANG Rong
Chin. Phys. Lett. 2012, 29 (5):
058501
.
DOI: 10.1088/0256-307X/29/5/058501
We investigate the leakage current of ultra-shallow Ni-silicided SiGe/Si junctions for 45 nm CMOS technology using a Si cap layer and the pre-amorphization implantation (PAI) process. It is found that with the conventional Ni silicide method, the leakage current of a p+(SiGe)–n(Si) junction is large and attributed to band-to-band tunneling and the generation-recombination process. The two leakage contributors can be suppressed quite effectively when a Si cap layer is added in the Ni silicide method. The leakage reduction is about one order of magnitude and could be associated with the suppression of the agglomeration of the Ni germano-silicide film. In addition, the PAI process after the application of a Si cap layer has little effect on improving the junction leakage but reduces the sheet resistance of the silicide film. As a result, the novel Ni silicide method using a Si cap combined with PAI is a promising choice for SiGe junctions in advanced technology.
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Conductance and DNA Translocation Current Blockage of Solid-State Nanopores
LU Bo,JIN Wei-Liang,ZHAO Qing**,YU Da-Peng**
Chin. Phys. Lett. 2012, 29 (5):
058701
.
DOI: 10.1088/0256-307X/29/5/058701
The current blockage during DNA molecule translocation through a solid-state nanopore is very important in DNA analysis techniques based on nanopores. We use Poisson–Nernst–Planck descriptions of electrolyte behavior in a nanopore with and without the presence of DNA molecules to simulate the nanopore conductance and current blockage of DNA molecules. Actual experimental parameters, such as pore size, length of nanopores, DNA drift velocity, and the charge issue of nanopores and DNA, are applied to evaluate the precise current blockage amplitude, which is found to agree very well with the experimental results.
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Statistical Physics of Economic Systems: a Survey for Open Economies
TAO Yong*,CHEN Xun
Chin. Phys. Lett. 2012, 29 (5):
058901
.
DOI: 10.1088/0256-307X/29/5/058901
We extend the theoretical framework of an independent economy developed by Tao [ Phys. Rev. E 82 (2010) 036118] so as to include multiple economies. Since the starting point of our framework is on the basis of the theory of the competitive markets of traditional economics, this framework shall be suitable for any free market. Our study shows that integration of world economies can decrease trade friction among economic systems, but may also cause a global economic crisis whenever economy disequilibrium occurs in any one of these economic systems.
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68 articles
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