Nonclassical Properties Of Excited Entangled Coherent States

Recently, with the development of quantum mechanics, quantum information theory has become one of the frontest areas in physics and information science. Quantum mechanics is composed of theory foundation of modern physics with relativity. Quantum entanglement has been the focus of much work in the foundations of quantum mechanics, being particularly with quantum nonsepa-rability, the violation of Bell's inequalities, and the so-called Einstein-Pololsky-Rosen (EPR) paradox. Beyond this fundamental aspect, creating and manipulating of entangled states are essential for quantum information applications. Among these applications are quantum computation, quantum teleportation, quantum dense coding, quantum cryptography, and quantum positioning and clock synchronization. Hence, quantum entanglement has been viewed as an essential resource for quantum information processing.This thesis is devoted to investigating the nonclassical properties of excited entangled coherent states: In chaper 2, we introduce the nonclassical properties of quantum states. Involving squeezing, sub-Poissonian photon statistics and anticorrelation. We describe simply the theory of quantum entanglement. Our tasks are from chaper 3 to 5, In chaper 3, We have introduced the SMEECSs through actions of a creation operator of a single-mode optical field on the ECS. We have investigated mathematical properties and entanglement characteristics of the SMEECSs, and discussed the influence of photon excitations on quantum entanglement. It has been shown that the SMEECSs form a new type of cyclic representation of the Heisenberg-Weyl algebra, i.e., the excited entangled-state representation. It has been found that the photon excitations affect seriously entanglement character of the SMEECSs in the weak field case. We have observed the much rich entanglement properties of the SMEECSs. It has been found that in most cases, the photon excitations lead to the decrease of the entanglement amount of the |Ψ_{α, m}>. In chaper 4, we investigate the nonclassical properties of single-mode excited entangled coherent states SMEECSs (|Ψ₊(α, m)> and |Ψ_{α, m}>, involving squeezing,sub-Poissonian photon statistics and anticorrelation. We find that omode and b mode of \^>+(a,m)) and |\I>_{a, m}) possess sub-Poissonian character. The SMEECS has different sub-Poissonian photon statistics in different strength regimes of the optical fields. It, has been found that in most cases, the photon excitations enhance the sub-Poissonian photon statistics of the SMEECS. we find that two modes of \^+(a,m)) is no anticorrelated aspect. However, this anticorrelated aspect in case of j\I/_a.m), in addition, the degree of anticorrelated aspect is deeper and deeper with increasing the number of the photon excitations m. Interestingly, Interestingly, there is squeezing in only one direction of the SMEECSs. The photon excitations lead to suppress the squeezing of the |\t+(a, m)), but the photon excitations lead to enhance the squeezing of the |^_{a, m}). In chaper 5, Two kinds of two-mode,sum and difference squeezing properties of the two-mode excited entangled coherent states IV'm) = A/"m(at - iti)m(\a, p) + | - a, -/?)), m = (0,1, 2...) have been discussed in this chaper. we discussed the influence of photon excitations on squeezing properties of two-mode excited entangled coherent states. The squeezing in both Indirection and ^direction of the two-mode excited entangled coherent states becomes stronger with increasing the number of the photon excitations in. This implies that the photon excitations enhance the sum squeezing properties of the two-mode excited entangled coherent states, we discussed the influence of photon excitations on squeezing properties of two-mode excited entangled coherent states in case of a = (3. We also discussed the difference squeezing properties of two-mode excited entangled coherent states. It is found that no squeezing is found for the variable Wi, but it is squeezed in Indirection. We can see that difference squeezing properties of the two-mode excited entangled coherent states becomes stronger with increasing the number of the photon excitations m. At last, we have also introduce how the two-mode excited entangled coherent states can be produced G.S.Agarwal have use a three-level A system to prepare the vortex state.