共查询到20条相似文献,搜索用时 140 毫秒
1.
A. I. Trubilko 《Journal of Experimental and Theoretical Physics》2012,114(4):575-588
The general kinetic equation for an isolated two-level atom and a high-Q cavity mode in a heat bath exhibiting quantum correlations (entangled bath) is applied to the analysis of the squeezed states of the collective system. Two types of collective operators are introduced for the analysis: one is based on bosonic commutation relations, and the other, on the commutation relations of the algebra obtained by a polynomial deformation of the angular momentum algebra. On the basis of these relations, formulas for observables are constructed that identify squeezed states in the system. It is shown that, under certain conditions, the collective system exhibits dual squeezing within the relations for boson operators, as well as for the operators constructed from the angular momentum algebra. Such squeezing is demonstrated under a projective measurement of an atom and for an entanglement swapping protocol. In the latter case, when measuring two initially independent atomic systems, depending on the type of measurement, two cavity modes collapse into a nonseparable state, which is described either by a nonseparability relation based on boson operators or by a relation based on the operators of the algebra of the quasimomentum of the collective system consisting of these two modes. 相似文献
2.
We investigate the entanglement between two atoms in an overdamped cavity injected with squeezed vacuum when these two atoms are initially prepared in coherent states. It is shown that the stationary entanglement exhibits a strong dependence on the initial state of the two atoms when the spontaneous emission rate of each atom is equal to the collective spontaneous emission rate, corresponding to the case where the two atoms are close together. It is found that the stationary entanglement of two atoms increases with decreasing effective atomic cooperativity parameter. The squeezed vacuum can enhance the entanglement of two atoms when the atoms are initially in coherent states. Valuably, this provides us with a feasible way to manipulate and control the entanglement, by changing the relative phases and the amplitudes of the polarized atoms and by varying the effective atomic cooperativity parameter of the system, even though the cavity is a bad one. When the spontaneous emission rate of each atom is not equal to the collective spontaneous emission rate, the steady-state entanglement of two atoms always maintains the same value, as the amplitudes of the polarized atoms varies. Moreover, the larger the degree of two-photon correlation, the stronger the steady-state entanglement between the atoms. 相似文献
3.
It is shown that the interaction of a system of two two-level atoms with a resonance classical electromagnetic field under conditions of collective relaxation gives rise to quantum correlations and controlled entanglement. Various models of the bath are examined, such as the unidirectional, one-dimensional, and three-dimensional models, as well as a squeezed bath. As a measure of the entanglement, the minimum negative eigenvalue of the Peres-Horodecki matrix is used. 相似文献
4.
The master equation is derived for an atom and a single high-Q cavity mode interacting with the bath modes produced by a two-mode broadband source based on two degenerate optical parametric oscillators. The relaxation superoperator, found in the resonant and dispersive limits, contains new terms describing correlations between the atom and the cavity mode. Collective coherent states are introduced to show that squeezed states of the atom-cavity subsystem are generated via interaction with an entangled environment. It is shown that a correlated initial state of the atom and the cavity mode manifests itself in two cavity QED phenomena: spontaneous atomic emission in the strong-coupling regime and population inversion in the Jaynes-Cummings model. 相似文献
5.
Jing Zhang 《Optics Communications》2007,277(2):353-358
As an important parameter, von Neumann entropy has been used to characterize the entanglement between atom and light field. We discussed the entanglement and nonclassicality evolution of an atom in a squeezed vacuum—a typical nonclassical field, and compare it with that of the coherent state. It shows that the atom-field entanglement in squeezed vacuum is much stronger and stabler than that in coherent state, whereas the nonclassicality of the light field depends on its initial status. This investigation is trying to find a new insight into the relation between entanglement of atom-field system and nonclassicality of light fields. The result shows that the entanglement between the atom and the field can be maintained well in the squeezed vacuum and this implies better control of atom and photon mutually. 相似文献
6.
A system consisting of two different atoms interacting with a two-mode vacuum, where each atom is resonant only with one cavity mode, is considered. The effects of dipole-dipole (dd) interaction between two atoms on the atom-atom entanglement and mode--mode entanglement are investigated. For a weak dd interaction, when the atoms are initially separable, the entanglement between them can be induced by the dd interaction, and the entanglement transfer between the atoms and the modes occurs efficiently; when the atoms are initially entangled, the entanglement transfer is almost not influenced by the dd interaction. However, for a strong dd interaction, it is difficult to transfer the entanglement from the atoms to the modes, but the atom-atom entanglement can be maintained when the atoms are initially entangled. 相似文献
7.
Elham Faraji Mohammad Kazem Tavassoly Hamid Reza Baghshahi 《International Journal of Theoretical Physics》2016,55(5):2573-2587
In this paper, we study the interaction between two Λ-type three-level atoms (a typical qutrit-qutrit system) and two coupled modes of a quantized radiation field in the presence of field-field interaction (parametric down conversion) which are simultaneously injected within an optical cavity. Then, by applying an appropriate canonical transformation, the introduced model is reduced to a well-known form of the generalized Jaynes-Cummings model. Under particular initial conditions for atoms (in some possible states) and the fields (in the finite dimensional pair coherent state) which may be prepared, the explicit form of the state vector of the whole system is analytically evaluated. In order to find the degree of entanglement between different parts of subsystems (“atom+atom”-field, “atom+field”-atom and atom-atom) the dynamics of entanglement through different measures, namely, linear entropy and negativity is evaluated. In each case, the effect of various types of initial atomic states on the above measures are numerically analyzed, in detail. It is indicated that the amount of entanglement can be tuned by choosing appropriate initial states of atoms. Particularly, it is shown that the entanglement sudden death (ESD) can be controlled by adjusting the initial state of the atoms. 相似文献
8.
We show that for a fixed amount of entanglement, two-mode squeezed states are those that maximize Einstein-Podolsky-Rosen-like correlations. We use this fact to determine the entanglement of formation for all symmetric Gaussian states corresponding to two modes. This is the first instance in which this measure has been determined for genuine continuous variable systems. 相似文献
9.
Negativity has been adopted to investigate the entanglement in a system composed of a two-level atom and a two-mode cavity field. Effects of Kerr-like medium and the number of photon inside the cavity on the entanglement are studied. Our results show that atomic initial state must be superposed, so that the two cavityfield modes can be entangled. Moreover, we also conclude that the number of photon in the two cavity mode should be equal. The interaction between modes, namely, the Kerr effect, has a significant negative contribution. Note that the atom frequency and the cavity frequency have an indistinguishable effect, so a corresponding approximation has been made in this article. These results may be useful for quantum information in optics systems. 相似文献
10.
C. Trallero-Giner V. López-Richard Y. Núñez-Fernández M. Oliva G. E. Marques M. C. Chung 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(7):1-5
Quadrature squeezed cylindrically polarized modes contain entanglement not only in the polarization and spatial electric field variables but also between these two degrees of freedom [C. Gabriel et al., Phys. Rev. Lett. 106, 060502 (2011)]. In this paper we present tools to generate and detect this entanglement. Experimentally we demonstrate the generation of quadrature squeezing in cylindrically polarized modes by mode transforming a squeezed Gaussian mode. Specifically, ?1.2 dB ± 0.1 dB of amplitude squeezing are achieved in the radially and azimuthally polarized mode. Furthermore, theoretically it is shown how the entanglement contained within these modes can be measured and how strong the quantum correlations are, depending on the measurement scheme. 相似文献
11.
Q. H. Liao G. Y. Fang Y. Y. Wang M. A. Ahmad S. Liu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(2):475-479
We consider two independent Jaynes-Cummings models which
consist of an atom interacts with electromagnetic field modes. The
generation of atom-atom entanglement is investigated. No direct
interaction between the two atoms exists. Entanglement can be
created using entanglement swapping method by an interference
measurement performed on photons. We discuss the influence of
off-resonance and the initial state of the atom on the atom-atom
entanglement. It is shown that the maximal atom-atom entanglement
can be obtained and the atom-atom entanglement is sensitive to the
off-resonance and the initial state of the atom. 相似文献
12.
Quantifying non-classical correlations under thermal effects in a double cavity optomechanical system
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《中国物理 B》2020,(2)
We investigate the generation of quantum correlations between mechanical modes and optical modes in an optomechanical system,using the rotating wave approximation.The system is composed of two Fabry-Perot cavities separated in space;each of the two cavities has a movable end-mirror.Our aim is the evaluation of entanglement between mechanical modes and optical modes,generated by correlations transfer from the squeezed light to the system,using Gaussian intrinsic entanglement as a witness of entanglement in continuous variables Gaussian states,and the quantification of the degree of mixedness of the Gaussian states using the purity.Then,we quantify nonclassical correlations between mechanical modes and optical modes even beyond entanglement by considering Gaussian geometric discord via the Hellinger distance.Indeed,entanglement,mixdness,and quantum discord are analyzed as a function of the parameters characterizing the system(thermal bath temperature,squeezing parameter,and optomechanical cooperativity).We find that,under thermal effect,when entanglement vanishes,purity and quantum discord remain nonzero.Remarkably,the Gaussian Hellinger discord is more robust than entanglement.The effects of the other parameters are discussed in detail. 相似文献
13.
Based on the fact that a two-mode squeezed number state is a
two-variable Hermite polynomial excitation of the two-mode squeezed
vacuum state, the result of one-mode l-photon measurement for the
two-mode squeezed number state $S_2|m,n\rangle$ is discussed. It is found that a remaining field-mode simultaneously
collapses into a number state $|n-m+l\rangle$ with
the coefficient being a Jacobi polynomial of n, m and l, which manifestly exhibits the entanglement
between the two modes, i.e. it depends on the number-difference
between the two modes. The second mode collapses into an excited
coherent state when the first mode is measured as a coherent state. 相似文献
14.
15.
A. I. Trubilko 《JETP Letters》2012,95(1):44-50
Collective operators corresponding to two different algebras have been introduced for a simple system consisting of a single
two-level atom and a high-quality cavity mode. The generators of the first algebra satisfy boson commutation relations, whereas
the generators of the second algebra have been obtained by polynomial deformation of su(2) algebra. It has been shown that
dual squeezed states identified using the considered commutation relations can be observed in the system placed in an entangled
bath with quantum correlations. 相似文献
16.
We introduce a scheme for creating continuous variable entanglement between an atomic beam and an optical field, by using squeezed light to outcouple atoms from a Bose-Einstein condensate via a Raman transition. We model the full multimode dynamics of the atom laser beam and the squeezed optical field and show that, with appropriate two-photon detuning and two-photon Rabi frequency, the transmitted light is entangled in amplitude and phase with the outcoupled atom laser beam. The degree of entanglement is controllable via changes in the two-photon Rabi frequency of the outcoupling process. 相似文献
17.
We present an experimental demonstration of both quadrature and polarization entanglement generated via the interaction between a coherent linearly polarized field and cold atoms in a high finesse optical cavity. The nonlinear atom-field interaction produces two squeezed modes with orthogonal polarizations which are used to generate a pair of nonseparable beams, the entanglement of which is demonstrated by checking the inseparability criterion for continuous variables recently derived by Duan et al. [Phys. Rev. Lett. 84, 2722 (2000)]] and calculating the entanglement of formation [Phys. Rev. Lett. 91, 107901 (2003)]]. 相似文献
18.
Dao-Ming Lu 《International Journal of Theoretical Physics》2011,50(6):1809-1818
We study the entanglement evolution between two atoms, which are initially entangled with a third atom and trapped in two
separated cavities coupled by an optical fiber. We also investigate the temporal evolution in the entanglement between the
atom and the local cavity mode. The influence of the state-selective measurement on the atom outside the cavities and the
influence of cavity-fiber coupling coefficient on the entanglement are discussed. The results show that the entanglement can
be strengthened through the state-selective measurement on the atom outside the cavities. We also find that, by increasing
the cavity-fiber coupling coefficient, the atom-atom entanglement is strengthened, but the atom-cavity entanglement is weakened. 相似文献
19.
采用Negativity熵来描述两子系统间的纠缠,研究了由两个二能级原子与光纤联接的单模腔构成的系统的纠缠特性.利用数值计算方法讨论了原子与腔场的耦合强度和原子选择性测量对纠缠特性的影响.研究结果表明:对一个原子的选择性测量,可增强原子间与腔场间和腔场与腔场间的纠缠. 相似文献
20.
If a two-level atom is in the two-photon resonance with a quantized mode and simultaneously inter-acts with a quasi-resonance classical field, then a photon exchange is observed in this system between the quantized and classical modes. It is demonstrated that such a physical system can serve as a source of squeezed radiation in the quantized mode. The squeezing can be arbitrarily close to unity, while the radiation amplitude can be relatively large. A situation is discussed when N atoms are in the two-photon resonance with a quantized mode and simultaneously interact with a classical field. The phenomenon of exponential superradiation is described when the number of photons in the quantized mode exponentially depends on the number N of atoms. 相似文献