期刊：
Journal of Physics B: Atomic, Molecular and Optical Physics,2009年42(5):055501- ISSN：0953-4075
通讯作者：
Li, Jingyan
作者机构：
[Hu, Xiangming; Li, Jingyan] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Li, Jingyan] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We analyse the effects of coherent or incoherent dressed population transfer on two-mode squeezing and continuous variable entanglement in four-wave mixing. Two cavity modes are generated from Rabi sidebands of dressed two-level atoms. A weak coherent or incoherent field couples one dressed state to an auxiliary excited state, from which the atoms decay to the other dressed state. This provides a two-step channel for dressed population transfer and reduces spontaneous emission into a squeeze-transformed mode that enters into an interaction with the dressed atoms. It is the reduction of spontaneous emission that leads to an enhancement of two-mode squeezing, whose degree is increased to 75% compared with 50% for the two-level case. This corresponds to a significant enhancement of the continuous variable entanglement.
作者机构：
[Hu, Xiangming; Li, Xiaoxia] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Hu, Xiangming] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We examine the quantum correlations at steady state in a three-mode quantum-beat laser that operates well above threshold. The analysis is presented by employing the dressed-atom combination-mode picture, in which only one combination mode of three cavity fields is coupled to the active medium, while the other two combination modes are decoupled. For suitable operating conditions, the coupled mode has the intensity fluctuations below the shot noise, while the two decoupled modes retain in their vacuum states. This determines that all of the original modes exhibit sub-Poissonian statistics. When the system operates well above threshold, the van Loock-Furusawa inequality is satisfied, concluding that the genuine tripartite entanglement among three sub-Poissonian fields is established. Physically, the responsible mechanism is the combined effect of atomic coherence controlled correlated-spontaneous emission and intrinsic feedback.
作者机构：
[Hu Xiang-Ming; Zou Jin-Hua] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Zou Jin-Hua] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词：
CAVITY;TELEPORTATION;CHANNELS;SCHEME
摘要：
We show that entanglement concentration of unknown atomic entangled states is achieved via the implementation of entanglement swapping based on Raman interaction in cavity QED. A maximally entangled state is obtained from a pair of partially entangled states probabilistically. Due to Raman interaction of two atoms with a cavity mode and an external driving field, the influence of atomic spontaneous emission has been eliminated. Because of the virtual excitation of the cavity mode, the decoherence of cavity decay and thermal field is neglected.
作者机构：
[Hu, Xiang-ming; Zou, Jin-hua] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Hu, Xiang-ming] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We show that a quantum-beat system with incoherent pump or coherent driving produces an entangled sub-shot-noise laser that operates well above threshold. The numerical results and physical analyses are presented using the combination modes of the lasing fields. The relative mode is decoupled from the active medium and thus remains in its vacuum state, while the sum mode operates well above threshold and has sub-shot-noise. The quantum beat and the sum mode intensity noise reduction combine to yield entanglement between two bright beams and sub-Poissonian photon statistics of the respective beams.
作者机构：
[Hu Xiang-Ming; Peng Yan-Dong; Gong Cheng] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Hu Xiang-Ming] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词：
pulsars;x-ray spectra;relativity and gravitation;redshift
摘要：
We present a realistic and efficient scheme for sub-half-wavelength atom localization. This scheme is based on the phase-dependent electromagnetically induced transparency in a four-level system in the double-A configuration. We use a strong bichromatic field （one component of which is standing-wave field） as the driving components, and a weak bichromatic field as the probe components. By choosing the collective phase of the four applied components, the atom is localized in either of the two half-wavelength regions with 50% detecting probability when the absorption to the probe fields is detected.
作者机构：
[Yin, Jian-wu; Xu, Qing] Huanggang Normal Univ, Coll Phys Sci & Technol, Huanggang 438000, Hubei, Peoples R China.;[Hu, Xiang-ming] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Xu, Qing] H;Huanggang Normal Univ, Coll Phys Sci & Technol, Huanggang 438000, Hubei, Peoples R China.
摘要：
The discrepancies in the power spectrum of the light scattered by a coherently driven three-level atom are identified with the help of two methods [see, A. S. Manka et al., Phys. Rev. A 43, 3748 (1991); M. R. Ferguson et al., Phys. Rev. A 54, 2379 (1996)]. Moreover, the most prominent differences are the negative values as well as the greatly distorted profile in the spectrum. It is shown that the inhomogeneity or homogeneity of the two-time correlation Bloch vector equation is responsible for such discrepancies.
摘要：
We propose an alternative scheme for preparing N-qubit cluster state by using a frequency-modulated laser field to simultaneously illuminate the trapped ions. Selecting the index of modulation yields the selective mechanisms of coupling and decoupling between the internal and external states of the ions. Based on the selective mechanisms, the highly entangled cluster state is achieved. In our scheme, the vibration mode is only virtually excited. Thus the quantum operations are insensitive to the heating and lead to the high-fidelity quantum information processing.
期刊：
Journal of Physics B: Atomic, Molecular and Optical Physics,2008年41(3):035503- ISSN：0953-4075
通讯作者：
Xu, Qing
作者机构：
[Xu, Qing] Huanggang Normal Univ, Journal Editor Dept, Huanggang 438000, Hubei, Peoples R China.;[Yin, Jian-wu] Huanggang Normal Univ, Coll Phys Sci & Technol, Huanggang 438000, Hubei, Peoples R China.;[Hu, Xiang-ming] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Xu, Qing] H;Huanggang Normal Univ, Journal Editor Dept, Huanggang 438000, Hubei, Peoples R China.
摘要：
The resonance fluorescence from a three-level Λ atom is studied, in which each optical transition is driven by a coherent field and the metastable states are coupled to each other via a microwave field. It is shown that the fluorescence depends not only on the relative intensities of the coupling fields but also on the relative phase delay between the envelopes of the amplitudes of the three fields. For the case of equal intensity of the two coherent fields, the fluorescence is completely inhibited once the phase delay is set to be 0 or π, while the fluorescence emerges once the phase delay is changed to π/2; moreover, the fluorescence spectrum ultimately reverts to an ultranarrow triplet by decreasing the relative intensity of the coherent field to the microwave field.
作者：
Li Xiao-Qi*;Wang Jian;Wang Fei;Hu Xiang-Ming（胡响明）
期刊：
物理学报,2008年57(4):2236-2241 ISSN：1000-3290
通讯作者：
Li Xiao-Qi
作者机构：
[Hu Xiang-Ming; Li Xiao-Qi; Wang Jian; Wang Fei] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Li Xiao-Qi] Yunyang Normal Univ, Dept Phys, Danjiangkou 442700, Peoples R China.
通讯机构：
[Li Xiao-Qi] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
期刊：
Journal of Physics B: Atomic, Molecular and Optical Physics,2008年41(14):145505 ISSN：0953-4075
通讯作者：
Xu, Qing
作者机构：
[Yin, Jian-wu; Xu, Qing] Huanggang Normal Univ, Coll Phys Sci & Technol, Huanggang 438000, Hubei, Peoples R China.;[Hu, Xiang-ming] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Xu, Qing] H;Huanggang Normal Univ, Coll Phys Sci & Technol, Huanggang 438000, Hubei, Peoples R China.
摘要：
We study the effects of the non-rotating wave approximation (non-RWA) on the spontaneous emission of a Λ-type three-level atom, where the metastable states are coupled to a common excited state by a weak laser field and the lower-level doublet is driven by a strong microwave field. When the non-RWA is applied to the interaction of the atom with the microwave field, the spontaneous emission spectrum is comprised of a series of ultrasharp lines. The physical interpretation of the spectral characteristics is given in light of the dressed states.
作者机构：
[Hu Xiang-Ming; Li Qian; Zhong Wen-Xue] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Hu Xiang-Ming] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词：
Radiation;Reservoir;Coherent Population Trapping;Einstein-Podolsky-Rosen (EPR)
摘要：
We show that it is possible to generate Einstein–Podolsky–Rosen (EPR) entangled radiation using an atomic reservoir controlled by coherent population trapping. A beam of three-level atoms is initially prepared in near-coherent population trapping (CPT) state and acts as a long-lived coherence-controlled reservoir. Four-wave mixing leads to amplification of cavity modes resonant with Rabi sidebands of the atomic dipole transitions. The cavity modes evolve into an EPR state, whose degree of entanglement is controlled by the intensities and the frequencies of the driving fields. This scheme uses the long-lived CPT coherence and is robust against spontaneous emission of the atomic beam. At the same time, this scheme is implemented in a one-step procedure, not in a two-step procedure as was required in Phys. Rev. Lett. 98 (2007) 240401.
通讯机构：
[Xu, Jun] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词：
sub-half-wavelength atom localization;interaction of light and matter;spontaneous emission spectrum
摘要：
We show that it is Possible to localize a two-level atom in a half-wavelength region by using a trichromatic field to drive the atom. Of the trichromatic components, one sideband is a standing-wave field with position-dependent amplitude. By varying the sum of relative phases of the sidebands of the trichromatic field to the central component, the atom is localized in either of the two half-wavelength regions with 50% detecting probability when the spontaneously emitted photons are detected. (C) 2008 Elsevier B.V. All rights reserved.
作者机构：
[Hu, Xiang-ming; Zhang, Xue-hua] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Hu, Xiang-ming] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We investigate the quantum noise in phase quadratures of resonance fluorescence from a two-level atom driven by a trichromatic exciting field. It is shown that the noise spectra are crucially dependent on the sum of relative phases of the sideband components compared to the central component although the sideband exciting components are much weaker than the central component. When we tune the exciting sidebands on two-photon resonance with the Mollow sideband transitions and set the phase sum to π, sideband squeezing in the in-phase quadrature remains almost the same as in the monochromatic case. Once the phase sum is set to zero, the squeezing is destroyed. The responsible mechanism is explained in terms of two-photon emission processes induced by the trichromatic components and the interference between these processes.
作者机构：
[Hu, Xiangming; Li, Qian; Cheng, Guangling; Zhong, Wenxue] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Hu, Xiangming] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We analyze quantum correlations in four-wave mixing in three-level Λ and V atomic systems by using dressed atomic states and squeeze-transformed cavity modes. Two dissipation channels are identified, through which the dressed atoms simultaneously absorb in the excitations from the pair of squeeze-transformed modes. It is in the presence of two channels that the entanglement is greatly enhanced and the best achievable state approaches the original Einstein-Podolsky-Rosen entangled state. This scheme is applicable in the optical regime where atomic spontaneous emission has to be taken into account, unlike the two-step atomic reservoir engineering scheme, which is limited to the microwave regime.
