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Microwave-Controlled Light-Pulse Propagation in a Driven A-Type Atomic System with Two-Folded Levels

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Communications in Theoretical Physics 2009年第7期52卷 137-142页

作者： YU Rong LI Jia-Hua SI Liu-Gang YANG Xiao-Xue School of Science Wuhan Institute of Technology Wuhan 430205 China Wuhan National Laboratory for Optoelectronics and School of Physics Huazhong University of Science and Technology Wuhan 430074 China

The temporal and spatial dynamics of one weak probe laser pulse, propagating through a A-type atomic medium with two-folded levels under the resonant excitation of one microwave driving field and one strong control field, is investigated in this paper. By numerically solving coupled Bloch-Maxwell equations, it is found that, in the absence of the microwave driving field, the atomic medium is transparent to the probe pulse at line center, which propagates over sufficiently long distances. By contrast, when the microwave driving field is applied, the probe pulse at line center can be rapidly absorbed on propagation. This substantial reduction of probe transmittance caused by the microwave driving field may lead to potential applications in designing a new kind of optical switching.

关键词： probe absorption and transmittance double-dark resonances (DDRs) switching

Carrier-Envelope Phase-Dependent Atomic Coherence and Its Detection Scheme

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Communications in Theoretical Physics 2008年第4期49卷 1022-1024页

作者： YANG Xiao-Xue WU Ying Physics Department Huazhong University of Science and Technology Wuhan 430074 China

The carrier-envelope phase （CEP） of few-cycle laser pulses is shown to have profound effects on the bound- state atomic coherence even in the weak-field regime where ionizations hardly take place, and a simple schem... 详细信息

关键词： carrier-envelope phase ultrafast processes atomic coherence

A robust method for frequency stabilization of 556-nm laser operating at the intercombination transition of ytterbium

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Chinese Optics Letters 2011年第4期9卷 60-63页

作者：熊转贤龙云肖辉星张曦贺凌翔吕宝龙 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and MathematicsChinese Academy of Sciences Graduate University of the Chinese Academy of Sciences

A frequency-stabilized 556-nm laser is an essential tool for experimental studies associated with ^1S0-^3p1 intercombination transition of ytterbium （Yb） atoms. A 556-nm laser light using a single-pass second harmonic generation （SHG） is obtained in a periodically poled MgO：LiNbO3 （PPLN） crystal pumped by a fiber laser at 1111.6 nm. A robust frequency stabilization method which facilitates the control of laser frequency with an accuracy better than the natural linewidth （187 kHz） of the intercombination line is developed. The short-term frequency jitter is reduced to less than 100 kHz by locking the laser to a home-made reference cavity. A slow frequency drift is sensed by the 556-nm fluorescence signal of an Yb atomic beam excited by one probe beam and is reduced to less than 50-kHz by a computer-controlled servo system. The laser can be stably locked for more than 5 h. This frequency stabilization method can be extended to other alkaline-earth-like atoms with similar weak intercombination lines.

关键词： Atoms Fiber lasers Frequency stability Harmonic generation Jitter Optical frequency conversion Stabilization Ytterbium

Controllable Optical Bistability and Multistability in a Four-Level Atomic System with Closed-Loop Configuration

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Chinese Physics Letters 2007年第1期24卷 108-111页

作者：吕新友李家华刘继兵 Department of Physics Huazhong University of Science and Technology Wuhan 430074

We theoretically investigate optical bistability （OB） and multistability （OM） behaviour of a closed-loop configuration atomic system driven by a degenerate coupling- field and a degenerate probe field inside a unidirectional ring cavity. It is found that the OB and OM behaviour can be controlled by adjusting- the intensity and the frequency detuning of the coupling- field, respectively. Interestingly, our numerical results show that it is easy to realize the transition from OB to OM or vice versa by adjusting- the intensity of the coupling- field under a appropriate frequency detuning. The effect of the atomic cooperation parameter on the OB behaviour is also discussed.

关键词： QUANTUM optics COUPLINGS (Gearing) ATOMS DEGENERATE differential equations

Preparation of Entanglement and Schrdinger Cat States of Superconducting Quantum Interference Devices Qubits via Coupling to a Microwave Cavity

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Communications in Theoretical Physics 2008年第3期49卷 643-648页

作者： YANG Wen-Xing Department of Physics Southeast University Nanjing 210096 China Wuhan Institute of Physics and Mathematics the Chinese Academy of Sciences Wuhan 430071 China

An alternative scheme is proposed for the generation of n-qubit W states of superconducting quantum interference devices （SQUID） in cavity QED. In this scheme, Raman coupling of two lower flux states of SQUID system is achieved via a microwave pulse and the cavity mode. Conditioned on no photon leakage from the cavity, the n-qubit W state can be generated whether the effective coupling parameters of the SQUID to cavity mode and classical microwave fields are the same or different. Our strictly numerical simulations of the time evolution of the system including decay show that the success probability of our scheme is almost unity and the interaction time is on the order of 10-9 s. The scheme can also be used to generate the Schrodinger cat states of multi-SQUID.

关键词： entanglement superconducting cavity

Jnconventional Geometric Phase Gate with Superconducting Quantum Interference Device Qubits in Cavity QED

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Communications in Theoretical Physics 2008年第4期49卷 913-918页

作者： YANG Wen-Xing CHEN Ai-Xi Department of Physics Southeast University Nanjing 210096 China State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Center for Cold Atom Physics Wuhan Institute of Physics and Mathematics the Chinese Academy of Sciences Wuhan 430071 China Department of Physics East China Jiaotong University Nanchang 330013 China

In the system with superconducting quantum interference devices （SQUID） in cavity, a scheme for constructing two-qubit quantum phase gate via a conventional geometric phase-shift is proposed by using a quantized cavity field and classical microwave pulses. In this scheme, the gate operation is realized in the subspace spanned by the two lower flux states of the SQUID system mud the population operator of the excited state has no effect on it. Thus the effect of decoherence caused from the levels of the SQUID system is possible to minimize. Under cavity decay, our strictly numerical simulation shows that it is also possible to realize the unconventional geometric phase gate. The experimental feasibility is discussed in detail.

关键词： superconducting quantum interference devices cavity QED geometric quantum gates

Maximized cooling efficiency for a Zeeman slower operating at optimized magnetic field profile

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Chinese Optics Letters 2011年第1期9卷 1-4页

We build a Zeeman slower with consecutive coils and use it to load an Yb magneto-optical trap （MOTs）. Cooling efficiency is measured by the fluorescence intensity of the atomic cloud trapped by the MOT. An optimized magnetic field profile can acquire the maximum cooling efficiency, corresponding to a good compromise between the smaller magnetic field mismatch and the high capture velocity. Our studies provide useful information on how the performance of the Zeeman slower can be improved.

关键词： Magnetic fields Magnetic refrigeration Optimization Ytterbium

Dynamics of Two-Level Trapped Ion in a Standing Wave Laser in Noncommutative Space

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Communications in Theoretical Physics 2007年第5期47卷 921-926页

作者： YANG Xiao-Xue WU Ying Department of Physics Huazhong University of Science and Technology Wuhan 430074 China

We study the dynamics of a two-level trapped ion in a standing wave electromagnetic field in two-dimensional （2D） noncommutative spaces in the Lamb-Dicke regime under the rotating wave approximation. We obtain the explicit analytical expressions for the energy spectra, energy eigenstates, unitary time evolution operator, atomic inversion, and phonon number operators. The Rabi oscillations, the collapse, and revivals in the average atomic inversion and the average phonon number are explicitly shown to contain the information of the parameter of the space noncommutativity, which sheds light on proposing new schemes based on the dynamics of trapped ion to test the noncommutativity.

关键词： two-level trapped ion noncommutative space

Effective Two-State Model and NOON States for Double-Well Bose-Einstein Condensates in Strong-Interaction Regime

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Communications in Theoretical Physics 2009年第8期52卷 244-246页

作者： YANG Xiao-Xue WU Ying Department of Physics Huazhong University of Science and Technology Wuhan 430074 China Department of Physics Hubei Normal University Huangshi 435002 China

The model of double-well Bose-Einstein condensates in the strong-interaction regime is shown to reduce adiabatically to an effective two-state model describing the Rabi oscillations between the two atomic Fock states ｜N, 0〉 and [0, N〉, and the NOON states of arbitrary ultracold atoms can therefore be generated periodically from the initial state of either one of the Foek states.

关键词： double-well Bose-Einstein condensates effective two-state model NOON states