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Adaptive Variable Structure Control of MIMO Nonlinear Systems with Time-varying Delays and Unknown Dead-zones

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International Journal of Automation and computing 2009年第2期6卷 124-136页

作者： tian-Ping zhang cai-Ying Zhou Qing Zhu Department of Automation College of Information Engineering Yangzhou University Yangzhou 225009 PRC

In this paper, adaptive variable structure neural control is presented for a class of uncertain multi-input multi-output （MIMO） nonlinear systems with state time-varying delays and unknown nonlinear dead-zones. The unknown time-varying delay uncer- tainties are compensated for using appropriate Lyapunov-Krasovskii functionals in the design. The approach removes the assumption of linear function outside the deadband without necessarily constructing a dead-zone inverse as an added contribution. By utilizing the integral-type Lyapunov function and introducing an adaptive compensation term for the upper bound of the residual and optimal approximation error as well as the dead-zone disturbance, the closed-loop control system is proved to be semi-globally uniformly ultimately bounded. In addition, a modified adaptive control algorithm is given in order to avoid the high-frequency chattering phenomenon. Simulation results demonstrate the effectiveness of the approach.

关键词： Adaptive control neural networks (NNs) variable structure control dead-zone nonlinear time-varying delay systems.

Single-photon source with sub-MHz linewidth for cesium-based quantum information processing

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Frontiers of physics 2023年第6期18卷 275-281页

作者： Hai He Peng-Fei Yang Peng-Fei zhang Gang Li tian-cai zhang State Key Laboratory of Quantum Optics and Quantum Optics Devices Collaborative Innovation Center of Extreme OpticsInstitute of Opto-ElectronicsShanxi UniversityTaiyuan 030006China

A single-photon source with narrow bandwidth,high purity,and large brightness can efficiently interact with material qubits strongly coupled to an optical microcavity for quantum information ***,we experimentally demonstrate a degenerate doubly resonant single-photon source at 852 nm by the cavity-enhanced spontaneous parametric downconversion process with a 100%duty cycle of *** single photon source possesses both high purity with a second-order correlation g^((2))_(h)(0)=0.021 and narrow linewidth with△_(V_(sp))=(800±13)*** single-photon s Single-photon source with sub-MHz linewidth for cesium-based quantum information processingource is compatible with the cesium atom D2 line and can be used for cesium-based quantum information processing Single-photon source with sub-MHz linewidth for cesium-based quantum information processing0.021.

关键词： single-photon source sub-MHz linewidth few longitudinal modes quantum information processing

Influence of pump intensity on atomic spin relaxation in a vapor cell

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Chinese Physics B 2019年第11期28卷 339-343页

作者： Chen Yang Guan-Hua Zuo Zhuang-Zhuang tian Yu-Chi zhang tian-cai zhang State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-ElectronicsShanxi UniversityTaiyuan 030006China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China College of Physics and Electronics Engineering Shanxi UniversityTaiyuan 030006China

Atomic spin relaxation in a vapor cell, which can be characterized by the magnetic resonance linewidth(MRL),is an important parameter that eventually determines the sensitivity of an atomic magnetometer. In this paper, we have extensively studied how the pump intensity affects the spin relaxation. The experiment is performed with a cesium vapor cell, and the influence of the pump intensity on MRL is measured at room temperature at zero-field resonance. A simple model with five atomic levels of a Λ-like configuration is discussed theoretically, which can be used to represent the experimental process approximately, and the experimental results can be explained to some extent. Both the experimental and the theoretical results show a nonlinear broadening of the MRL when the pump intensity is increasing. The work helps to understand the mechanism of pump induced atomic spin relaxation in the atomic magnetometers.

关键词： atomic magnetometer atomic spin relaxation optical pumping

Extending the trapping lifetime of single atom in a microscopic far-off-resonance optical dipole trap

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Frontiers of physics 2011年第3期6卷 262-270页

作者： Jun HE Bao-dong YANG Yong-jie CHENG tian-cai zhang Jun-min WANG State Key Laboratory of Quantum Optics and Quantum Optics Devices and Institute of Opto Electronics Shanxi University Taiyuan 030006 China

In our experiment, a single cesium atom prepared in a large-magnetic-gradient magneto optical trap （MOT） can be efficiently transferred into a 1064-nm far-off-resonance microscopic optical dipole trap （FORT）. The efficient transfer of the single atom between the two traps is used to determine the trapping lifetime and the effective temperature of the single atom in FORT. The typical trapping lifetime has been improved from ~ 6.9 s to ~ 130 s by decreasing the background pressure from 1 × 10^-10 Torr to ~ 2 × 10^-11 Torr and applying one-shot 10-ms laser cooling phase. We also theoretically investigate the dependence of trapping lifetimes of a single atom in a FORT on trap parameters based on the FORT beam＇s intensity noise induced heating. Numerical simulations show that the heating depends on the FORT beam＇s waist size and the trap depth. The trapping time can be predicted based on effective temperature measurement of a single atom in the FORT and the intensity noise spectra of the FORT beam. These experimental results are found to be in agreement with the predictions of the heating model.

关键词： magneto optical trap (MOT) far-off-resonance optical dipole trap (FORT) singleatom trapping lifetime release-and-recapture method (R&R) effective temperature

Comparison of single-neutral-atom qubit between in bright trap and in dark trap

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Chinese Physics B 2019年第2期28卷 192-196页

作者： Ya-Li tian Zhi-Hui Wang Peng-Fei Yang Peng-Fei zhang Gang Li tian-cai zhang State Key Laboratory of Quantum Optics and Quantum Optics Devices and Institute of Opto-ElectronicsShanxi University Collaborative Innovation Center of Extreme Optics Shanxi University

A single neutral atom is one of the most promising candidates to encode a quantum bit(qubit). In a real experiment, a single neutral atom is always confined in a micro-sized far off-resonant optical trap(FORT). There are generally two types of traps: red-detuned trap and blue-detuned trap. We experimentally compare the qubits encoded in "clock states" of single cesium atoms confined separately in either 1064-nm red-detuned(bright) trap or 780-nm blue-detuned(dark) trap: both traps have almost the same trap depth. A longer lifetime of 117 s and a longer coherence time of about 10 ms are achieved in the dark trap. This provides a direct proof of the superiority of the dark trap over the bright trap. The measures to further improve the coherence are discussed.

关键词： single qubit laser trapping coherence time

10-Hertz squeezed light source generation on the cesium D_(2)line using single photon modulation

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Frontiers of physics 2023年第3期18卷 167-174页

作者： Guan-Hua Zuo Yu-Chi zhang Gang Li Peng-Fei zhang Peng-Fei Yang Yan-Qiang Guo Shi-Yao Zhu tian-cai zhang State Key Laboratory of Quantum Optics and Quantum Optics Devices Collaborative Innovation Center of Extreme OpticsInstitute of Opto-ElectronicsShanxi UniversityTaiyuan 030006China College of Physics and Electronic Engineering Shanxi UniversityTaiyuan 030006China Department of Physics Zhejiang UniversityHangzhou 310027China Key Laboratory of Advanced Transducers and Intelligent Control System Ministry of Education and Shanxi ProvinceCollege of Physics and OptoelectronicsTaiyuan University of TechnologyTaiyuan 030024China

Generation of squeezed light source is a promising technique to overcome the standard quantum limit in precision ***,we demonstrate an experimental generation of quadrature squeezing resonating on the cesium D_(2)line down to 10 Hz for the first *** maximum squeezing in audio frequency band is 5.57 ***,we have presented a singlephoton modulation locking to control the squeezing angle,while effectively suppressing the influence of laser noise on low-frequency *** whole system operates steadily for *** generated low-frequency squeezed light source can be applied in quantum metrology,light–matter interaction investigation and quantum memory in the audio frequency band and even below.

关键词： squeezed state optical parametric amplifier low-frequency squeezing

Optimization of a magneto–optic trap using nanofibers

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Chinese Physics B 2019年第7期28卷 198-201页

作者： Xin Wang Li-Jun Song Chen-Xi Wang Peng-Fei zhang Gang Li tian-cai zhang State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-Electronics Shanxi University Taiyuan 030006 China Collaborative Innovation Center of Extreme Optics Shanxi University Taiyuan 030006 China

We experimentally demonstrate a reliable method based on a nanofiber to optimize the number of cold atoms in a magneto–optical trap(MOT) and to monitor the MOT in real *** atomic fluorescence is collected by a nanofiber with subwavelength diameter of about 400 *** MOT parameters are experimentally adjusted in order to match the maximum number of cold atoms provided by the fluorescence collected by the *** maximum number of cold atoms is obtained when the intensities of the cooling and re-pumping beams are about 23.5 mW/cm^2 and 7.1 mW/cm^2,respectively;the detuning of the cooling beam is-13.0 MHz, and the axial magnetic gradient is about 9.7 Gauss/*** observe a maximum photon counting rate of nearly(4.5 ± 0.1)× 10^5 counts/*** nanofiber–atom system can provide a powerful and flexible tool for sensitive atom detection and for monitoring atom–matter *** can be widely used from quantum optics to quantum precision measurement.

关键词： nanofiber magneto–optic trap optimization fluorescence efficient coupling

Tunable Optical Bandpass Filter via a Microtip-Touched Tapered Optical Fiber

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Chinese Physics Letters 2020年第10期37卷 26-32页

作者： Peng-Fei zhang Li-Jun Song Chang-Ling Zou Xin Wang Chen-Xi Wang Gang Li tian-cai zhang State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-ElectronicsShanxi UniversityTaiyuan 030006China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China CAS Key Laboratory of Quantum Information University of Science and Technology of ChinaHefei 230026China

We demonstrate a tunable bandpass optical filter based on a tapered optical fiber(TOF)touched by a hemispherical microfiber tip(MFT).Other than the interference and selective material absorption effects,the filter relies on the controllable and wavelength-dependent mode–mode interactions in ***,a large range of tunability is realized by controlling the position of the MFT in contact with the TOF for various TOF radii,and two distinct bandpass filter mechanisms are *** center wavelength of the bandpass filter can be tuned from 890 nm to 1000 nm,while the FWHM bandwidth can be tuned from 110 nm to 240 nm when the MFT touches the TOF in the radius range from 160 nm to 390 *** distinction ratio can reach 28±3 dB *** combined TOF-MFT is an in-line tunable bandpass optical filter that has great application potential in optical networks and spectroscopy,and the principle could also be generalized to other integrated photonic devices.

关键词： tunable fiber Touch

Cavity enhanced measurement of trap frequency in an optical dipole trap

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Chinese Physics B 2019年第4期28卷 165-169页

作者： Peng-Fei Yang Hai He Zhi-Hui Wang Xing Han Gang Li Peng-Fei zhang tian-cai zhang State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-ElectronicsShanxi University Collaborative Innovation Center of Extreme Optics Shanxi University

We demonstrate a direct, fluorescence-free measurement of the oscillation frequency of cold atoms in an optical dipole trap based on a high-finesse optical cavity strongly coupled to atoms. The parametric heating spectra of the trapped atoms are obtained by recording the transmitted photons from the cavity with the trap depth is modulated by different ***, in our method the oscillation can be observed directly in the time scale. Being compared to the conventional fluorescence-dependent method, our approach avoids uncertainties associated with the illuminating light and auxiliary imaging optics. This method has the potential application of determining the motion of atoms with stored quantum bits or degenerate gases without destroying them.

关键词： cavity QED oscillation frequency