Symmetry of Lagrangians of nonholonomic systems of non-Chetaev’s type

This paper studies the symmetry of Lagrangians of nonholonomic systems of non-Chetaev's type. First, the definition and the criterion of the symmetry of the system are given. Secondly, it obtains the condition under which there exists a conserved quantity and the form of the conserved quantity. Finally, an example is shown to illustrate the application of the result.     

Teleportation of an arbitrary mixture of diagonal states of multiqudit

This paper proposes a scheme to teleport an arbitrary mixture of diagonal states of multiqutrit via classical correlation and classical communication. To teleport an arbitrary mixture of diagonal states of N qutrits, N classically correlated pairs of two qutrits are used as channel. The sender （Alice） makes Fourier transform and conditional gate （i.e., XOR（3） gate） on her qutrits and does measurement in appropriate computation bases. Then she sends N ctrits to the receiver （Bob）. Based on the received information, Bob performs the corresponding unitary transformation on his qutrits and obtains the teleported state. Teleportation of an arbitrary mixture of diagonal states of multiqudit is also discussed.     

Influence of Self-Interaction ofσ Meson to the Equation of State of Nuclear Matter

In the relativistic σ-ωmodel, the influence of the parameters in self-interaction of a meson to the equation of state of normal nuclear matter, especially, to incompressibility, effective mass, and coupling constants, is studied in detail. We find that these parameters have an intense relationship to the property of nuclear matter. At the same time , we study the relation between the binding energy and pressure of relativestic △-resonance nuclear matter and temperature using using above results in the relativistic σ-ω-π model,and it is interesting to compare it to our prior work. In all these studies, the vacuum fluctuation on nucleon, △-isobar, and σmeson is considered.     

Analysis of the causes of formation of negative loss factors

I-IatroductionStatisticalEnergyAnalysis(SEA)isakindofeffective,simpleanddirectapproachforan-alyzingvibrationandsound,andithasbeenfoundwidelyapplicationsinanalysisofmechanicalnoiseandvibrationcolltrolsince198osl1-4].However,forgeneralindustrialmachineswhichalwayconsistofcomPlexandheaVystructures,thedeterminationmethodsofSEAparametersintheclassicalSEAtheoryareinapplicable[5]because:(1)SEAparametersofthesekindsofstructuresaredifficulttoobtainfromthetheory(2)theconditionofconservativeandweak…     

Measurement-device-independent quantum key distribution of multiple degrees of freedom of a single photon

Measurement-device-independent quantum key distribution(MDI-QKD)provides us a powerful approach to resist all attacks at detection side.Besides the unconditional security,people also seek for high key generation rate,but MDI-QKD has relatively low key generation rate.In this paper,we provide an efficient approach to increase the key generation rate of MDI-QKD by adopting multiple degrees of freedom(DOFs)of single photons to generate keys.Compared with other high-dimension MDI-QKD protocols encoding in one DOF,our protocol is more flexible,for our protocol generating keys in independent subsystems and the detection failure or error in a DOF not affecting the information encoding in other DOFs.Based on above features,our MDI-QKD protocol may have potential application in future quantum comniunication field.     

Department of Physics Renmin University of China

Location Renmin University of China 59 Zhongguancun Ave.,Beijing 100872,China Futher Information:http:www.phys.ruc.edu.cn/Location Renmin University is one of top universities in China.The Department of Physics was founded in the fall of 2005.The Department has 35 full-time faculty members,including 20 professors,12 associate professors,and 3 lecturers.Their orientation is high-quality research combined with physics instruction across the full spectrum of core subjects.The activities of the department are designed to exploit the intrinsic synergy of innovative research teaching and academic exchanges in physics and related disciplines all of which are pursued at an internationally recognized standard.     

Improvement of Synchronizability of Scale-Free Networks

We investigate the factors that affect synchronizability of coupled oscillators on scale-free networks. Using the memory Tabu search （MTS） algorithm, we improve the eigen-ratio Q of a coupling matrix by edge intercrossing. The numerical results show that the synchronizatlon-improved scale-free networks should have distinctive both small average distance and larger clustering coefficient, which are consistent with some real-world networks. Moreover, the synchronizability-improved networks demonstrate the disassortative coefficient.     

Analysis of Frequency Spectrum of Laser-Induced Vibration of Microbeam Resonators

The vibration phenomenon during pulsed laser heating of micro-beams is investigated. The beam is made of silicon and is heated by a laser pulse with a non-Gaussian temporal profile and with an ultrashort pulse duration of 2ps, which incites vibration due to the thermoelastic damping effect. This coupled thermoelastic problem is solved using an analytical-numerical technique based on the Laplace transformation. The damping ratio and resonant frequency shift ratio of beams due to the air damping effect and the thermoelastic damping effect are also examined and discussed.     

Influence of the net gain on characteristic of stochastic resonance in a single-mode laser system

The phenomenon of stochastic resonance (SR) is found in a single-mode laser system driven by the colored pump noise with signal modulation and the quantum noise with cross-correlation between the real and imaginary parts. When the net gain a0 changes, it is found that, 1) the shape of the curve of the signal-tonoise ratio (SNR) versus the pump noise self-correlation time T exhibits a changing process of multiform SR, from single-peak SR to simultaneous existence of resonances and suppressions; 2) the curve of SNR versus signal frequency Ω experiences a complicated changing process from the monotonous descending to the simultaneous appearances of a maximum and a minimum, and finally to monotonous descending; 3)the curve of SNR versus cross-correlation coefficient between the real and imaginary parts of the quantum noise λq appears an acute single-peak SR. Therefore, the net gain a0 greatly influences the characteristic of SR of laser system.     

Stochastic resonance in a gain--noise model of a single-mode laser driven by pump noise and quantum noise with cross-correlation between real and imaginary parts under direct signal modulation

Stochastic resonance (SR) is studied in a gain--noise model of a single-mode laser driven by a coloured pump noise and a quantum noise with cross-correlation between real and imaginary parts under a direct signal modulation. By using a linear approximation method, we find that the SR appears during the variation of signal-to-noise ratio (SNR) separately with the pump noise self-correlation time \tau , the noise correlation coefficient between the real part and the imaginary part of the quantum noise \lambda_q , the attenuation coefficient \gamma and the deterministic steady-state intensity I_0 . In addition, it is found that the SR can be characterized not only by the dependence of SNR on the noise variables of \tau and \lambda_q, but also by the dependence of SNR on the laser system variables of \gamma and I₀. Thus our investigation extends the characteristic quantity of SR proposed before.     

Stochastic Resonance in a Single-Mode Laser Driven by Pump Noise and Quantum Noise with Cross-Correlated Real and Imaginary Parts

We present an analytic investigation of the signal-to-noise ratio (SNR) by studying a signal modulated model of a single-mode laser system driven by pump noise and quantum noise with correlated real and imaginary parts,and find there is a maximum in the curve of the dependence of SNR upon the cross-correlation coefficient λq between the real part and the imaginary part, i.e., stochastic resonance appears in the SNR vs. λq curve. Moreover, when the SNR is at the maximum, the cross-correlation coefficient λq = O, which is coincidentally at the minimum of the mean normalized intensity fluctuation. The influences on stochastic resonance by the intensities of the pump and the quantum noise, the amplitude of the modulation signal, and the net gain of the laser are also studied. Furthermore, in order to ensure that the results obtained in this paper is reliable, the valid range for the linear approximation method is discussed.     

Stochastic resonance of bias signal-modulated noise in a single-mode laser＊

Stochastic resonance (SR) for bias signal modulation is studied in a single-mode laser system. By investigating a gain-noise model driven by correlated pump noise and quantum noise, we find that, whether the correlation coefficient between both the noises is positive or negative, SR always appears in the dependence of signal-to-noise ratio (SNR) upon the noise correlation time and the frequency of the modulation signal. However, only when the correlation coefficient between both noises is negative can SR occur in the dependence of SNR upon the quantum noise intensity and pump noise intensity, while when the correlation coefficient between both noises is positive, it shows monotonically.     

信号调制色泵噪声和实虚部间关联量子噪声驱动下单模激光的随机共振现象

计算了受信号调制的色泵噪声和实虚部间关联的量子噪声驱动的单模激光损失模型的输出光强信噪比.发现信噪比R随泵噪声自关联时间τ、调制信号频率Ω和量子噪声实虚部间关联系数λq的变化均存在随机共振,这种现象扩展了“信噪比R对噪声强度的变化曲线具有极大值”的典型随机共振. 若以Ω为参数,当Ω增加时,Ｒ随τ的关系曲线经历了从同时出现共振和抑制到单峰共振,最后到单调上升的变化,呈现多种形式的随机共振．若以τ为参数,当τ增加时,Ｒ随Ω的关系曲线经历了从单调上升到同时出现共振和抑制,最后又到单调下降的变化过程．Ｒ随λq的关 关键词： 噪声 信噪比 随机共振     

偏置调幅波调制噪声的单模激光随机共振

采用偏置信号的调幅波调制抽运噪声的单模激光增益模型，用线性化近似方法计算了以e指数形式关联的两色噪声驱动下光强的功率谱及信噪比.结果表明，信噪比随着噪声强度的变化、抽运噪声自关联时间的变化、激光系统参数的变化、载波频率及信号频率的变化均存在随机共振现象. 关键词： 抽运噪声 单模激光 随机共振 调幅波     

Stochastic resonance for signal-modulated pump noise in a single-mode laser

By adopting the gain-noise model of the single-mode laser in which with bias and periodical signals serve as inputs, combining with the effect of coloured pump noise, we use the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity under the condition of pump noise and quantum noise cross-related in the form of δ function. It is found that with the change of pump noise correlation time, both SNR and the output power will occur stochastic resonance (SR). If the bias signal α is very small, changing the intensities of pump noise and quantum noise respectively does not lead to the appearance of SR in the SNR; while α increases to a certain number, SR appears.     

Influence of Signal and Noise on Statistical Fluctuation of Single-Mode Laser System

On the basis of calculating the steady-state mean normalized intensity fluctuation of a signal-mode laser system driven by both colored pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts, we analyze the influence of modulation signal, noise, and its correlation form on the statistical fluctuation of the laser system. We have found that when the amplitude of modulation signal weakens and its frequency quickens, the statistical fluctuation will reduce rapidly. The statistical fluctuation of the laser system can be restrained by reducing the intensity of pump noise and quantum noise. Moreover, with prolonging of colored cross-correlation time, the statistical fluctuation of laser system experiences a repeated changing process, that is, from decreasing to augmenting,then to decreasing, and finally to augmenting again. With the decreasing of the value of cross-correlation coefficient, the statistical fluctuation will decrease too. When the cross-correlation form between the real part and imaginary part of quantum noise is zero correlation, the statistical fluctuation of laser system has a minimum. Compared with the influence of intensity of pump noise, the influence of intensity of quantum noise on the statistical fluctuation is smaller.     

Influence of Signal and Noise on Statistical Fluctuation of Single-Mode Laser System

On the basis of calculating the steady-state mean normalized intensity fluctuation of a signal-mode laser system driven by both colored pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts, we analyze the influence of modulation signal, noise, and its correlation form on the statistical fluctuation of the laser system. We have found that when the amplitude of modulation signal weakens and its frequency quickens, the statistical fluctuation will reduce rapidly. The by reducing the intensity of pump noise and quantum noise. statistical fluctuation of the laser system can be restrained Moreover, with prolonging of colored cross-correlation time, the statistical fluctuation of laser system experiences a repeated changing process, that is, from decreasing to augmenting, then to decreasing, and finally to augmenting again. With the decreasing of the value of cross-correlation coe~cient, the statistical fluctuation will decrease too. When the cross-correlation form between the real part and imaginary part of quantum noise is zero correlation, the statistical fluctuation of laser system has a minimum. Compared with the influence of intensity of pump noise, the influence of intensity of quantum noise on the statistical fluctuation is smaller.     

Stochastic Resonance in a Single-Mode Laser Driven by Quadratic Colored PumpNoise: Effects of Biased Amplitude Modulation Signal

A single-mode laser noise model driven by quadratic colored pump noise andbiased amplitude modulation signal is proposed. The analytic expression ofsignal-to-noise ratio is calculated by using a new linearized procedure. Itis found that there are three different typies of stochastic resonance inthe model: the conventional form of stochastic resonance, the stochasticresonance in the broad sense, and the bona fide SR.