共查询到20条相似文献,搜索用时 15 毫秒
1.
Fu-li Li Zhang-qi Yin 《量子光学学报》2006,12(B08):75-75
Two atomic clusters, which have NA and Ns two-level atoms, respectively, are placed in a cavity but separated spatially. There is no direct interaction between the atoms. All the atoms interact with a single-mode of the cavity field. Quantum entanglement between the two atomic clusters is investigated for various initial states of the two atomic clusters and the field. When the cavity field is initially in a Fock state, we find that the time evolution of entanglement quasi-periodically oscillates regardless of the initial states of atoms. The oscillation period increases as the initial photon number increases. When all the atoms in both of the atomic clusters are initially in the excited state, we show that there is no entanglement between the atomic clusters with NA = NB = 1 regardless the initial state of the cavity field. However, when either NA or NB is larger than one, we find that the entanglement always exists even for a strong thermal field. In cases with different initial states of the atomic clusters, we notice that the entanglement becomes stronger as number of the atoms increases. When all the atoms in both of the clusters in the ground state, we also find that the entanglement can be enhanced even by a thermal field. We also notice that a single qubit can be entangled with multi-atoms which are initially in the ground state by the cavity field initially being in vacuum, thermal, coherent, and squeezed states. 相似文献
2.
We provide a model to investigate feedback control of entanglement.
It consists of two distant (two-level) atoms
which interact through a radiation field
and becomes entangled.
We then show the possibility to stabilize such entanglement against
atomic decay by means of a feedback action. 相似文献
3.
Quantum entanglement in the system of two two-level atoms interacting with a single-mode vacuum field 总被引:5,自引:0,他引:5
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The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investigated by using the quantum reduced entropy; the quantum entanglement between two two-level atoms, and that between a single two-level atom and a single-mode vacuum field are studied in terms of the quantum relative entropy. The influences of the atomic dipole--dipole interaction on the quantum entanglement of the system are also discussed. Our results show that three entangled states of two atoms--field, atom--atom, and atom--field can be prepared via two two-level atoms interacting with a single-mode vacuum field. 相似文献
4.
Considering a quantum model consisting of two effective two-level atoms and a single-mode cavity,this paper investigates the entanglement dynamics between the two atoms,and studies the effect of the Stark shift on the entanglement.The results show that,on the one hand the atom-atom entanglement evolves periodically with time and the periods are affected by the Stark shift;on the other hand,the two atoms are not disentangled at any time when the Stark shift is considered,and for large values of the Stark shift parameter,the two atoms can remain in a stationary entangled state.In addition,for the initially partially entangled atomic state,the atom-atom entanglement can be greatly enhanced due to the presence of Stark shift.These properties show that the Stark shift can be used to control entanglement between two atoms. 相似文献
5.
利用超算符方法求解幅值损耗腔中两个∧型三能级原子与相干光场相互作用系统的主方程,并利用量子条件熵研究了两个初始为|Ψa(0)>和|Φa(0)>纠缠态的原子与光场作用过程中原子的纠缠演化特性.讨论了不同初始原子纠缠度,不同耗散系数以及不同平均光子数对两原子纠缠度的影响.结果表明:①当原子初始处于|Ψa(0)>类纠缠态时,其纠缠度随光场强度以及腔场衰减系数演化.当腔不存在耗散时,纠缠度呈周期性振荡;当腔存在耗散时,纠缠度呈衰减振荡并趋于稳定值;且光强越弱,其稳定值越大;衰减系数越大纠缠达到稳定值所需时间越短.②原子初始处于|Φa(0)>类纠缠态时,其纠缠度只与原子初始纠缠度有关,不随其他因素变化. 相似文献
6.
Considering two identical two-level atoms interacting
with a single-mode thermal
field through two-photon processes,
this paper studies the atomic coherence control on the
entanglement between two two-level atoms,
and finds that the entanglement is greatly
enhanced due to the initial atomic coherence. The results show
that the entanglement can be manipulated
by changing the initial
parameters of the system, such as the superposition coefficients
and the relative phases
of the initial atomic coherent state and the mean photon
number of the cavity field. 相似文献
7.
研究了光纤耦合腔A和B中各囚禁一个和两个二能级原子的情况,给出了总激发数为1时系统态矢的演化。采用Negativity熵来描述两个子系统间的纠缠,利用数值计算方法研究了腔内原子与原子间和腔场与腔场间的纠缠特性,讨论了光纤模与腔场间的耦合强度变化对纠缠特性的影响。另一方面还研究了对腔A中原子选择性测量对纠缠特性的影响。研究结果表明:随光纤模与腔场间的耦合系数增大,腔场间纠缠减弱。原子间纠缠与光纤模与腔场间的耦合系数间存在非线性关系。另一方面,采用原子态选择性测量方法,可增强腔内原子间和腔场间的纠缠。 相似文献
8.
闫丽 《原子与分子物理学报》2019,36(6)
本文将两个二能级原子注入一个腔中,用共生纠缠的方法来度量两原子之间的纠缠并推出它们之间的量子失协,还给出了原子与环境之间的共生纠缠与量子失协的计算公式,讨论了原子自发衰变率的变化对量子纠缠及失协的影响,及不同的初始状态情况下,纠缠及失协随原子距离的演化情况。结果表明:原子自发衰变率减小,原子与环境之间的量子纠缠及失协增加;选择不同的初态,可以控制原子间出现纠缠死亡的现象或量子失协为零的状态。 相似文献
9.
闫丽 《原子与分子物理学报》2017,34(4):716-721
本文将两个二能级原子注入一个腔中,用共生纠缠的方法来度量两原子之间的纠缠并推出它们之间的量子失协,还给出了原子与环境之间的共生纠缠与量子失协的计算公式,讨论了原子自发衰变率的变化对量子纠缠及失协的影响,及不同的初始状态情况下,纠缠及失协随原子距离的演化情况.结果表明:原子自发衰变率减小,原子与环境之间的量子纠缠及失协增加;选择不同的初态,可以控制原子间出现纠缠死亡的现象或量子失协为零的状态. 相似文献
10.
Considering two identical two-level atoms interacting with two mode thermalfield through a nondegerate two-photon process, we study the entanglement dynamics between two atoms when the atomic coherence exists. It shows that the entanglement is dependent on the initial atomic states, and is greatlyenhanced due to atomic coherence as compared with the case when the atomic coherence is ignored. The results also show that the entanglement can be controlled by changing the relative phases and the amplitudes of the polarized atoms. 相似文献
11.
闫丽 《原子与分子物理学报》2018,35(6)
本文将两个二能级原子注入一个腔中,用共生纠缠的方法来度量两原子之间的纠缠并推出它们之间的量子失协,还给出了原子与环境之间的共生纠缠与量子失协的计算公式,讨论了原子自发衰变率的变化对量子纠缠及失协的影响,及不同的初始状态情况下,纠缠及失协随原子距离的演化情况。结果表明:原子自发衰变率减小,原子与环境之间的量子纠缠及失协增加;选择不同的初态,可以控制原子间出现纠缠死亡的现象或量子失协为零的状态。 相似文献
12.
Perfect quantum state mirroring in a chain of N spins is defined as the condition in which the state |iof the chain is swapped into the state |N-i within a time evolution interval τ.Such a phenomenon is an interesting way of transfering entanglement.An expressions for the perfect mirroring of a single qubit contained in a spin chain were proposed in the past.We exploit such an expressions for calculating the evolution times in chains of both two and three spins.In the case of a chain of two qubits,we derive conditions under which the associated four Bell states diagonalize the Hamiltonian.It is found that for the two Bell states |Φ+and|Φ-,perfect mirroring does not occur(i.e.entanglement is not preserved under swapping).On the other hand,perfect single qubit mirror effect(entanglement preservation) indeed occurs for the other two Bell states |Ψ+and|Ψ- which are mapped into |Φ+and|Φ-respectively.For the case of a chain of three qubits,the effects of a perfect single qubit mirroring on a set of four maximally entangled three qubit states ψ1,ψ2,χ1,and χ2 are studied.Due to the fact that quantum mirroring preserves maximal entanglement,the states ψ1 and ψ2 are not altered.However,quantum mirroring changes the states χ1 and χ2 only if we apply perfect quantum state mirroring in the site a=1 of the three qubits spin chain.The above constrains the preservation of maximal entanglement under qubit mirroring of such a state.Due to the fact that swapping has already been experimentally tested,a posible experimental implementations of single qubit mirroring is possible. 相似文献
13.
Dao-Ming Lu 《International Journal of Theoretical Physics》2012,51(7):2119-2126
Three two-level atoms are trapped in two initially empty cavities connected by an optical fiber. The entanglement evolution between two atoms in the same cavity and the entanglement evolution between two cavities are investigated. The influence of the state-selective measurement of the atom trapped in the other cavity on the entanglement and that of fiber-cavity coupling coefficient on the entanglement are discussed. The results obtained show that atom-atom entanglement property is strengthened, and cavity-cavity entanglement property is weakened with increasing of the cavity-fiber coupling coefficient. On the other hand, the results also show that the entanglement between two cavities and that between two atoms in the same cavity can be strengthened through the state-selective measurement on the atom trapped in the other cavity. 相似文献
14.
Dao-Ming Lu 《International Journal of Theoretical Physics》2013,52(9):3057-3065
This paper discusses the entanglement dynamics of a coupled cavity quantum electrodynamics (CQED) setup, which comprises three two-level atoms resonantly interacting with three cavities that are coupled by two optical fibers. The influences of atom-cavity coupling constant on the entanglement between atoms and that between cavities are discussed. The results obtained from the numerical method show that the entanglement between non-adjacent atoms or that between adjacent cavities has a nonlinear relation with increasing of the atom-cavity coupling coefficient. On the other hand, the entanglement between non-adjacent cavities is strengthened and the entanglement between adjacent atoms is weakened with increasing of atom-cavity coupling constant. 相似文献
15.
16.
Considering a double JC model, this paper investigates the quantum discord dynamics of two isolated moving two-level atoms
each interacting with a single-mode thermal cavity field, and studies the effect of the atomic motion and the field-mode structure
on quantumdiscord. The results show that, on the one hand the quantum discord evolves periodically with time and the periods
are affected by the atomic motion and the field-mode structure; on the other hand, the quantum discord still can capture the
quantum correlation between the two atoms when the entanglement is zero. It is interesting to note that the quantum discord
can be effectively preserved by controlling the field-mode structure parameter 相似文献
17.
We study three-body entanglement induced by spontaneous
emission in a three two-level atoms system by using the entanglement
tensor approach. The results show that the amount of entanglement
is strongly dependent on the initial state of the system and the species
of atoms. The three-body entanglement is the result of the coherent
superposition of the two-body entanglements. The larger the
two-body entanglement is, the stronger the three-body entanglement
is. On the other hand, if there exists a great difference in three two-body entanglement measures,
the three-body entanglement is very weak.
We also find that the maximum of the two-body entanglement
obtained with nonidentical atoms is greater than that obtained
with identical atoms via adjusting the difference in atomic frequency. 相似文献
18.
In this contribution, we investigate a TTLAs (two two-level atoms) in interaction with an electromagnetic field in presence of the external classical fields. The general solution of the time evolution operator is obtained and used to derive the density matrix operator. The temporal evolution of the atomic inversion, the degree of entanglement measured by the negativity, as well as the single atom entropy squeezing are discussed. We consider the atomic system at either the upper or Bell states, while the field in the coherent state. It has been shown that the coupling parameter g (the coupling of the external classical fields) gets more effective for the case in which the g is not equal to zero. Also for a strong coupling parameter g the superstructure phenomenon can be reported. The results shown that for increase the value of the classical external fields parameter leads to the entanglement between the atoms and the fields gets stronger. Also it has shown that for specific value of the classical external fields the system never reaches the pure state except during the revival periods. 相似文献
19.
两纠缠原子与相干态光场相互作用的动力学 总被引:21,自引:15,他引:6
采用时间演化算符和数值计算方法,研究了两全同二能级纠缠原子与相干态光场相互作用的动力学,结果表明:原子布居和偶极压缩特性与两原子体系纠缠度和相干态光场强度相关联. 相似文献
20.
《Physics letters. A》2006,360(2):309-316
We study evolution of entanglement of two two-level atoms placed inside a multilayered microsphere. We show that due to inhomogeneity of the optical field modes this entanglement essentially depends on the atomic positions (asymmetrical entanglement) and also on the detuning between the atomic transitions and field frequencies. The robust and complete entanglement can be achieved even in the resonant case when the atoms have different effective coupling constants, and it can be extended in time if the detuning is large enough. 相似文献