摘要:
We examine the role of coherences on the creation of multi-mode entanglement in a nanomechanical cavity containing a finite size one-dimensional optical lattice. We show that, in general, the system is composed of three coupled modes and find that the presence of the first-order coherence between two modes of the system is equally effective in destroying entanglement between them. In the case of two modes coupled through an intermediate mode we show that there is no entanglement between the modes when both modes are coupled to the intermediate mode by the parametric interaction. We find that in order to effectively entangle the modes, one of the modes should be coupled to the intermediate mode by a parametric interaction but the other mode should be coupled by the linear-mixing interaction.
作者机构:
[Li, Gao-xiang; Huang, Hui; Gu, Wen-ju] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Ficek, Zbigniew] KACST, Natl Ctr Math & Phys, Riyadh 11442, Saudi Arabia.
通讯机构:
[Huang, Hui] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
We investigate the effects of a low-frequency (acoustic) phonon bath on the dynamics of a quantum dot modeled as a cascade three-level system. We show that the phonon bath appears to the upper transition of the cascade system as a broadband reservoir of inverted rather than conventional harmonic oscillators. The action of the annihilation and creation operators of the inverted oscillator are interchanges relative to those of the usual harmonic oscillator that it serves as a linear amplifier to the system, and thereby gives rise to unusual features in the dynamics of the quantum dot. We find that the phonon bath, although being in a thermal state, affects the quantum dot as a correlated-type reservoir which results in the decay of the system to a correlated two-photon state with the population distribution no longer obeying a Boltzmann distribution. It is particularly interesting that even for a zero-temperature phonon reservoir, the steady state is a correlated state which, under appropriate conditions on the Rabi frequencies and the damping rates, can reduce to a strongly correlated pure state. It is shown that the two-photon correlations result in a significant squeezing and strong two-photon correlations in the radiation field emitted by the quantum dot. The presence of the correlations in the system is manifest in the presence of quantum beats in the time evolution of the populations and the radiation intensity. The effect of the ordinary spontaneous emission on the features induced by the phonon bath is also discussed.
期刊:
European Physical Journal D,2014年68(1):15-null ISSN:1434-6060
通讯作者:
Zhou, Ben-Yuan
作者机构:
[Zhou, Ben-Yuan] Air Force Early Warning Acad, Basic Course Dept, Phys Teaching Sect, Wuhan 430019, Peoples R China.;[Cai, Ze-Bin] Air Force Early Warning Acad, Sci Res Dept, Wuhan 430019, Peoples R China.;[Li, Gao-Xiang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构:
[Zhou, Ben-Yuan] A;Air Force Early Warning Acad, Basic Course Dept, Phys Teaching Sect, Wuhan 430019, Peoples R China.
作者机构:
[Cerbu, Marcela; Macovei, Mihai A.] Moldavian Acad Sci, Inst Appl Phys, MD-2028 Kishinev, Moldova.;[Li, Gao-xiang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Cerbu, Marcela] Moldavian Acad Sci, Inst Appl Phys, Acad St 5, MD-2028 Kishinev, Moldova.
通讯机构:
[Cerbu, Marcela] M;Moldavian Acad Sci, Inst Appl Phys, Acad St 5, MD-2028 Kishinev, Moldova.
摘要:
We investigate the resonant cooling phenomena of a driven two-level radiator embedded in a photonic-crystal structure. We find that cooling occurs even at laser-atom-frequency resonance. This happens due to atomic dressed-state coupling with different strengths, resulting in population redistribution and cooling. Furthermore, for off-resonant driving the two-level particle can be in either the ground or excited bare state. This may help in the engineering of different amplified optical devices as well as highly coherent light sources.
作者机构:
[Li, Gao-xiang; Gu, Wen-ju] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Yang, Ya-ping] Tongji Univ, Dept Phys, Shanghai 200092, Peoples R China.
通讯机构:
[Gu, Wen-ju] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
We investigate the generation of squeezed states in a movable mirror in dissipative optomechanics in which the oscillating mirror modulates both the resonance frequency and the linewidth of the cavity mode. Via feeding broadband squeezed-vacuum light accompanying a coherent driving laser field into the cavity, the master equation for the cavity-mirror system is derived by following the general reservoir theory. When the mirror is weakly coupled to the cavity mode, we find that the driven cavity field can effectively perform as a squeezed-vacuum reservoir for the movable mirror via utilizing the completely destructive interference of quantum noise. Efficient transfer of squeezing from the light to the movable mirror occurs, irrespective of the ratio between the cavity damping rate and the mechanical frequency. Moreover, when the mirror is moderately coupled to the cavity mode, photonic excitation can preclude the completely destructive interference of quantum noise. As a consequence, the mirror deviates from the ideal squeezed state.
作者机构:
[Li, Gaoxiang; Tan, Huatang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Meystre, P.; Tan, Huatang] Univ Arizona, Dept Phys, Inst B2, Tucson, AZ 85721 USA.;[Meystre, P.; Tan, Huatang] Univ Arizona, Coll Opt Sci, Tucson, AZ 85721 USA.
通讯机构:
[Tan, Huatang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
In this paper, we propose two quantum optomechanical arrangements that permit the dissipation-enabled generation of steady two-mode mechanical squeezed states. In the first setup, the mechanical oscillators are placed in a two-mode optical resonator while in the second setup the mechanical oscillators are located in two coupled single-mode cavities. We show analytically that for an appropriate choice of the pump parameters, the two mechanical oscillators can be driven by cavity dissipation into a stationary two-mode squeezed vacuum, provided that mechanical damping is negligible. The effect of thermal fluctuations is also investigated in detail and shows that ground-state precooling of the oscillators is not necessary for the two-mode squeezing. These proposals can be realized in a number of optomechanical systems with current state-of-the-art experimental techniques.
作者机构:
[Yi, Zhen; Li, Gao-xiang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Yang, Ya-ping] Tongji Univ, Dept Phys, Shanghai 200092, Peoples R China.
通讯机构:
[Yi, Zhen] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
We propose a ground-state cavity-mediated cooling scheme for a trapped atom, which is in the Λ configuration and confined inside a high-finesse optical cavity, using a standing-wave cooling laser. The carrier transition can be prohibited by placing the atom at the node of the cavity field, and the blue-sideband transition can be simultaneously eliminated by exploiting quantum interference via tuning the frequency of the cooling laser. As a consequence, the ground-state cooling for the trapped atom can be achieved. Moreover, we numerically demonstrate the superiority by placing the atom at the antinode of the standing-wave cooling laser as compared with the running-wave cooling laser, and the robustness of the scheme using the standing-wave laser. Meanwhile, the cooling rate can reach the same order of magnitude as that obtained in the cavity–electromagnetically-induced-transparency cooling scheme, and the explicit expression for the final phonon number in higher order is also presented.
作者机构:
[Li, Gaoxiang; Tan, Huatang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Seok, H.; Buchmann, L. F.] Univ Arizona, Dept Phys, Inst B2, Tucson, AZ 85721 USA.;[Seok, H.; Buchmann, L. F.] Univ Arizona, Coll Opt Sci, Tucson, AZ 85721 USA.
通讯机构:
[Tan, Huatang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
In this paper, we propose a scheme for generating steady-state entanglement of remote micromechanical oscillators in unidirectionally coupled cavities. For the system of two mechanical oscillators, we show that when two cavity modes in each cavity are driven at red- and blue-detuned sidebands, respectively, a stationary two-mode squeezed vacuum state of the two mechanical oscillators can be generated by the cascaded cavity coupling. The degree of squeezing is controllable by adjusting the relative strength of the pump lasers. Our calculations also show that the achieved mechanical entanglement is robust against thermal fluctuations. For the case of multiple mechanical oscillators, we find that steady-state genuine multipartite entanglement can also be built up among the remote mechanical oscillators. The present scheme does not require nonclassical light input or conditional quantum measurements, and it can be realized with current experimental technology.
作者机构:
[Li, Gaoxiang; Tan, Huatang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Meystre, P.; Tan, Huatang; Bariani, F.] Univ Arizona, Dept Phys, Inst B2, Tucson, AZ 85721 USA.;[Meystre, P.; Tan, Huatang; Bariani, F.] Univ Arizona, Coll Opt Sci, Tucson, AZ 85721 USA.
通讯机构:
[Tan, Huatang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
We propose a scheme that exploits the combined effects of nonlinear dynamics and dissipation to generate macroscopic quantum superpositions in massive optomechanical oscillators. The effective degenerate three-wave mixing interaction between the mechanical and optical cavity modes that results from quadratic optomechanical coupling, together with the cavity dissipation, can result in the existence of dark macroscopic superpositions. We show analytically and confirm numerically that various quantum superpositions can be achieved deterministically, depending on the initial state of the mechanics. The effects of mechanical damping are also studied in detail and quantified by the negativity of the Wigner function. The present scheme can be realized in various optomechanical systems with current technology.
作者机构:
[Zhu, Jia-pei; Li, Gao-xiang; Huang, Hui] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Zhu, Jia-pei] Honghe Univ, Fac Sci, Mengzi 661100, Peoples R China.
通讯机构:
[Zhu, Jia-pei] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
We theoretically investigate the influence of the phonon-mediated coupling on the properties of the laser generated by a single red-detuned quantum dot (QD), where the QD is coherently driven and coupled to a microscopic cavity which can be engineered in a photonic band-gap (PBG) material. In the low-temperature limit, the phonon-mediated coupling is deleterious to the emission of photon into cavity field and the threshold behavior of the laser persists after the inclusion of the phonon-mediated processes. Without being engineered in the PBG material, if the damping rate κ of the cavity is close to but smaller than the phonon-mediated spontaneous emission rate γ of the dot, the photon statistics of the cavity field change from super-Poissonian to sub-Poissonian. The nonclassical effect can be achieved due to the phonon-mediated processes induced by the electron-phonon interaction and the off-resonant dot-cavity coupling. The nonclassical effect can be enhanced by the PBG material. When the effect of the thermal phonon is taken into account, the cavity field exhibits the super-Poissonian property. If κ is much smaller than γ, the phonon-mediated processes can lead to the increase (decrease) of the photons provided that the incoherent pumping rate is lower (higher) than the effective phonon-mediated threshold. But, if κ is close to or larger than γ, the emission of the photon may dominate the absorption process, strengthening the intensity of the cavity field.
期刊:
Journal of Physics B: Atomic, Molecular and Optical Physics,2013年46(3):035505 ISSN:0953-4075
通讯作者:
Deng, Wen-Wu
作者机构:
[Li, Gao-xiang; Deng, Wen-Wu] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Deng, Wen-Wu] Hubei Univ Sci & Technol, Inst Photon & Phototechnol, Xianning 437100, Peoples R China.
通讯机构:
[Deng, Wen-Wu] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
Based on a unitary transformation and a generalized rotating-wave approximation, the effect of the counter-rotating wave terms on the trace distance of quantum states for the qubit in the Rabi model is investigated. The analytical expressions of the eigenenergies and eigenstates of the qubit–field coupling system are obtained approximately. Starting from the two initial Bell states for the qubit and field, in which the qubit is in the same states, we find that the time evolution of the trace distance for the qubit states is only related to the difference between the populations in the qubit excited state but independent of the coherence of the qubit. The effect of the counter-rotating wave terms brings the trace distance of the quantum states of the qubit to exhibit fast oscillations in the strong coupling regime.
作者机构:
[Li, Gao-xiang; Gu, Wen-ju] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构:
[Gu, Wen-ju] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要:
We propose a fast ground-state optomechanical cooling scheme through the use of a two-mode optical cavity with a quarter-wave plate inside. Two cavity modes are orthogonally polarized; one cavity mode dissipates to the external environment at a fast rate while the other dissipates at a slow rate. The quarter-wave plate provides linear mixing interaction between these two cavity modes. The cooling process is dominated by scattering process via the fast-decay channel, which is significantly enhanced as compared with that obtained in the resolved-sideband optomechanical cooling scheme. Meanwhile, the heating process is significantly suppressed by exploiting the destructive quantum interference between the two cavity modes with the help of the quarter-wave plate.
作者机构:
[Li, Gao-xiang; Gu, Wen-ju] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构:
[Li, Gao-xiang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词:
Fano resonance;Optical amplifiers;Quantum fluctuations;Quantum information processing;Quantum noise;Squeezed states
摘要:
We investigate the generation of squeezed state of the mirror motion in a dissipative optomechanical system driven with a strong laser field accompanied with two periodically-modulated lights. Using the density operator approach we calculate the variances of quantum fluctuations around the classical orbits. Both the numerical and analytical results predict that the squeezed state of the mirror motion around its ground state is achievable. Moreover, the obtained squeezed state is robust against the thermal noise because of the strong cooling effect outside the resolved-sideband regime, which arises from the destructive interference of quantum noise.
摘要:
We propose a cooling scheme for a trapped atom using the phenomenon of cavity-induced double electromagnetically induced transparency (EIT), where the atom comprising of four levels in tripod configuration is confined inside a high-finesse optical cavity. By exploiting one cavity-induced EIT, which involves one cavity photon and two laser photons, carrier transition can be eliminated due to the quantum destructive interference of excitation paths. Heating process originated from blue-sideband transition mediated by cavity field can also be prohibited due to the destructive quantum interference with the additional transition between the additional ground state and the excited state. As a consequence, the trapped atom can be cooled to the motional ground state in the leading order of the Lamb-Dicke parameters. In addition, the cooling rate is of the same order of magnitude as that obtained in the cavity-induced single EIT scheme.