通讯机构：
[Li, Gao-Xiang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词：
quantum dots;shot noise;spin polarised transport
摘要：
We analyze theoretically the pumped spin current and its shot noise spectra in a two-level quantum dot system, where the dot is irradiated by circularly polarized light. The device operates at a certain chemical potential configuration in the absence of magnetic field and ferromagnetic spin injection. The spin-resolved shot noise can be modulated by the light nonmonotonously and always indicates a sub-Poissonian type.
摘要：
The spontaneous decay of a V-type three-level atom placed in a negative-refractive-index waveguide is analyzed. We find that in thin waveguides, highly efficient surface-guided modes are supported, which do not occur in positive-index waveguides. In addition, at low absorption, the mode density and thus spontaneous emission into particular regular-guided modes is enhanced by several orders of magnitude as compared to regular dielectric waveguides. The asymmetries between emission into the different modes and the enhancement of particular guided modes allow us to induce strong spontaneous emission interference between transitions with orthogonal transition dipole moments.
作者机构：
[Al-Amri, M.] KACST, Natl Ctr Math & Phys, Riyadh 11442, Saudi Arabia.;[Zubairy, M. Suhail; Al-Amri, M.] Max Planck Inst Kernphys, D-69117 Heidelberg, Germany.;[Al-Amri, M.; Li, Gao-xiang; Tan, Rong] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Zubairy, M. Suhail] Texas A&M Univ, Dept Phys, College Stn, TX 77843 USA.;[Zubairy, M. Suhail] Texas A&M Univ, Inst Quantum Studies, College Stn, TX 77843 USA.
通讯机构：
[Al-Amri, M.] K;KACST, Natl Ctr Math & Phys, POB 6086, Riyadh 11442, Saudi Arabia.
摘要：
We explore the entanglement dynamics of two qubits embedded in one-dimensional (1D) and three-dimensional (3D) photonic crystals. Our 1D results show sudden death and sudden birth of the entanglement, restricted by the initial coherence and the population in the excited state as well as the detuning. The results for the 3D crystal show entanglement death but no birth. We also discuss the entanglement of N qubits in the aforementioned photonic crystals.
期刊：
Journal of Physics B: Atomic, Molecular and Optical Physics,2009年42(12):125502- ISSN：0953-4075
通讯作者：
Li, Gao-xiang
作者机构：
[Tan, Hua-tang; Li, Gao-xiang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Xia, Hong-xing] Xiaogan Univ, Dept Comp Sci, Xiaogan 432000, Peoples R China.
通讯机构：
[Li, Gao-xiang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We investigate the effects of spontaneously generated interference on the spectrum of quantum fluctuations in phase quadratures of resonant fluorescence emitted from the transition of j = 1/2 to j = 1/2 of a monochromatically driven four-level atom with antiparallel dipole moments. It is found that the spectrum exhibits obvious characteristics of quantum interference in both cases of weak and strong laser fields. For the Zeeman-degenerate system, strong radiation squeezing in weak atomic excitation can occur at the central frequency of the spectrum, which is quite different from the case without consideration of the interference. Moreover, when we apply an external magnetic field to the atom, we find that the quantum interference can lead to a narrowing spectrum with much stronger squeezing by adjusting the magnetic field strength. These results suggest that the phase-dependent fluorescence spectrum can serve as a probe of the quantum interference effects in a realistic system such as a trapped 198Hg+ ion or charged quantum dots.
作者机构：
[Li, Gao-xiang; Wu, Shao-ping] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Wu, Shao-ping] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
Interference;Nonidentical atoms;Correlation function
摘要：
The interference property of the fluorescence field from two nonidentical atoms driven by a laser field is investigated. It is found that there are differences for the intensity and the second-order correlation function between the two identical atoms system and the two nonidentical atoms system. It is shown that the intensity and the second-order correlation function have different behaviors under the weak laser field and the strong case for two identical atoms and two nonidentical atoms systems.
作者机构：
[Zhang Li-Juan; Wu Shao-Ping; Li Gao-Xing] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Wu Shao-Ping] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词：
Decoherence;Kerr effect;Superoperator
摘要：
Considering a system in which a single photon and a coherent field propagate through a Kerr medium, when the weak cross-Kerr interaction between the coherent state and the single photon under decoherence is involved, this paper derives analytically a macroscopic superposition state by the superoperator method and investigates the influences of decoherence on the coherence properties of the obtained state. It finds that the macroscopic superposition state will experience evolution from a pure superposition state to a mixed state in a dissipative environment and the Kerr effect makes the field display a periodic revival from decoherence for a short time.
作者机构：
[Zhan Ming-Sheng; Zhou Lu] Chinese Acad Sci, Wuhan Inst Phys & Math, State Key Lab Magnet Resonance & Atom & Mol Phys, Wuhan 430071, Peoples R China.;[Zhan Ming-Sheng; Zhou Lu] Chinese Acad Sci, Ctr Cold Atom Phys, Wuhan 430071, Peoples R China.;[Zhou Lu] Chinese Acad Sci, Grad Sch, Beijing 100080, Peoples R China.;[Zhou Lu] E China Normal Univ, Dept Phys, State Key Lab Precis Spect, Shanghai 200062, Peoples R China.;[Li Gao-Xiang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Zhou Lu] C;Chinese Acad Sci, Wuhan Inst Phys & Math, State Key Lab Magnet Resonance & Atom & Mol Phys, Wuhan 430071, Peoples R China.
摘要：
We propose to generate two-mode squeezed vacuum motional state of an intracavity trapped ion by taking the advantage of the dissipation of the cavity mode. At the first step, the steady and pure two-mode motional entanglement between two motional degrees of the cold ion is obtained by engineering the couplings of both the motional modes of the ion to the cavity field. Based on the first step, a two-mode squeezed vacuum motional state is then generated by manipulating the phases of the external laser pulses incident on the ion.
通讯机构：
[Li, Gao-xiang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We study nonclassical and spectral properties of a strongly driven single-atom laser engineered within a photonic crystal that facilitates a frequency-dependent reservoir. In these studies, we apply a dressed atom model approach to derive the master equation of the system and study the properties of the dressed laser under the frequency-dependent transition rates. By going beyond the secular approximation in the dressed-atom cavity-field interaction, we find that if, in addition, the nonsecular terms are included into the dynamics of the system, then nonlinear processes can occur that lead to interesting aspects of cavity field behavior. We calculate variances of the quadrature phase amplitudes and the incoherent part of the spectrum of the cavity field and show that they differ qualitatively from those observed under the secular approximation. In particular, it is found that the nonlinear processes lead to squeezing of the fluctuations of the cavity field below the quantum shot noise limit. The squeezing depends on the relative population of the dressed states of the system and is found only if there is no population inversion between the dressed states. Furthermore, we find a linewidth narrowing below the quantum limit in the spectrum of the cavity field that is achieved only when the secular approximation is not made. An interpretation of the linewidth narrowing is provided in terms of two phase-dependent noise (squeezing) spectra that make up the incoherent spectrum. We establish that the linewidth narrowing is due to squeezing of the fluctuations in one quadrature phase components of the cavity field.
期刊：
Journal of Physics B: Atomic, Molecular and Optical Physics,2008年41(10):105501- ISSN：0953-4075
通讯作者：
Tan, Hua-tang
作者机构：
[Huang, Guang-ming; Tan, Hua-tang; Li, Gao-xiang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Tan, Hua-tang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
In this paper, we investigate the generation of entangled light via collectively interacting three-level cascade atoms in a two-mode cavity. It is found that the atomic collectivity can effectively increase the strength of the frequency down-conversion process in the system and lead to the significant enhancement of the entanglement between the two cavity modes, in comparison to the case of independent atoms.
期刊：
Journal of Physics B: Atomic, Molecular and Optical Physics,2008年41(15):155502 ISSN：0953-4075
通讯作者：
Li, Gao-xiang
作者机构：
[Tan, Hua-tang; Li, Gao-xiang; Deng, Wen-wu] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Deng, Wen-wu] Xianning Univ, Dept Phys, Xianning, Peoples R China.
通讯机构：
[Li, Gao-xiang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
The entanglement and squeezing properties of a two-mode field are investigated in the system of a double-ladder four-level atom embedded in a two-mode cavity. It is found that the system can reduce to the nondegenerate parametric oscillator which is responsible for the entanglement and squeezing of a cavity field under suitable conditions. Moreover, compared to the field from the three-level cascade atomic system, the degree of entanglement in the present system can be improved significantly.
作者机构：
[Li, Gao-Xiang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;Max Planck Inst Kernphys, D-69117 Heidelberg, Germany.
通讯机构：
[Li, Gao-Xiang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
The entanglement properties of two mode fields generated from four-wave mixing are discussed in the system of an ensemble of V-type three-level atoms embedded in a two-mode cavity, in which the atomic transitions from the two excited states to the ground state are driven by one strong and one relative weak laser field, respectively. The nondegenerate four-wave mixing process occurs in the strong laser-driven transition, which is also coupled by the two cavity modes. With the help of the auxiliary atomic transition driven by the weak laser field and adjusting the frequency difference of the two modes, highly squeezed and entangled light with high intensity can be generated.
期刊：
Journal of Physics B: Atomic, Molecular and Optical Physics,2007年40(3):555-564 ISSN：0953-4075
通讯作者：
Tan, Hua-tang
作者机构：
[Tan, Hua-tang] Hong Kong Baptist Univ, Dept Phys, Hong Kong, Hong Kong, Peoples R China.;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;Chinese Univ Hong Kong, Inst Theoret Phys, Hong Kong, Hong Kong, Peoples R China.
通讯机构：
[Tan, Hua-tang] H;Hong Kong Baptist Univ, Dept Phys, Hong Kong, Hong Kong, Peoples R China.
摘要：
By considering vibrational heating of an intracavity trapped ion and cavity damping, we investigate the effects of decoherence on entanglement and two-mode squeezing of output light from the cavity when the ion is excited continuously. It is found that the bright output light with the steady robust entanglement can be always achieved even in the presence of decoherence. Moreover, the entangled output light may not exhibit two-mode squeezing because the heating of the vibrational mode has stronger limitation on the two-mode squeezing than on the entanglement of the output light.
期刊：
Journal of Physics B: Atomic, Molecular and Optical Physics,2007年40(14):2827-2839 ISSN：0953-4075
通讯作者：
Ke, Sha-sha
作者机构：
[Ke, Sha-sha] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;Jianghan Univ, Dept Phys, Wuhan 430056, Peoples R China.
通讯机构：
[Ke, Sha-sha] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
The enhancement of the intracavity entanglement of a nonlinear coupler via homodyne-mediated quantum feedback is investigated. It is found that the feedback can effectively enhance the squeezing, entanglement and purity of a two-mode field in the nonlinear coupler by appropriately choosing the quadrature angle at which the quantum feedback is introduced.
作者机构：
[Tan, Hua-tang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;Hong Kong Baptist Univ, Dept Phys, Hong Kong, Peoples R China.
通讯机构：
[Tan, Hua-tang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
The generation of macroscopic and spatially separated three-mode entangled light for triply coupled χ(3) Kerr coupler inside a pumped optical cavity is investigated. With the linearized analysis for small perturbation around the steady state of the pumped cavity modes, the linearized Hamiltonian and the corresponding master equation are obtained. It is found that the bright three-mode squeezing and full inseparable entanglement can be achieved both inside and outside the cavity.
