量子纠缠与非经典效应等问题的研究

【作者】 高德营；

【导师】 夏云杰；

【作者基本信息】 曲阜师范大学 ， 理论物理， 2007， 硕士

【摘要】 量子信息学作为一个新兴学科，以量子计算机和量子通信为主要内容日益发展起来。它具有经典信息学无法比拟的优越性，作为量子信息学中的最基本资源——量子纠缠，一直是人们研究的课题。腔量子电动力学(腔QED)是原子物理与量子光学的交叉研究领域。它主要研究原子与特定边界条件下量子化光场的相互作用。对其研究能够揭示特殊条件下光与物质相互作用丰富的物理现象及其内在本质，并且在近年来兴起的量子信息领域内，腔QED方案被认为是最有效的量子信息方案之一；纠缠是经典理论无法解释现象，作为量子光学中一个重要内容的非经典效应同样是经典理论无法解释的现象，两者之间是否有关系一直是人们研究的问题。本论文主要研究了在腔QED中原子纠缠的演化特性及纠缠与非经典效应之间的关系，主要内容包括下面两部分：1．通过negativity方法，研究了两个空间分离的纠缠二能级原子依次通过高Q粒子数场时，两个原子的纠缠演化特性，发现：初始原子状态和光场状态对两原子的纠缠有明显的影响。通过选择初始状态可以得到较长时间的最大纠缠。然后与两个纠缠原子同时在高Q粒子场时两原子纠缠的演化做了有意义的比较。2．通过引入正交基矢，连续变量形式的纠缠相干态转化成分立形式，然后用concurrence方法计算了纠缠度，同时研究了其非经典效应(压缩效应，反聚束效应)。发现纠缠总是伴随着压缩效应和反聚束效应两者之一，并随相应非经典效应的增大而增大。更多还原

【Abstract】 Quantum information science, which mainly includes quantum computer and quantum communication, has increasingly evolved as a new object. And it exhibits a number of advantages corresponding to classical counterpart. Quantum entanglement which is the basic resources of quantum information science is always researched by people.Cavity quantum electrodynamics (QED) system is overlapping research area between the atomic physics and the quantum optics. It not only can help us to understand quantum effects and reveal the interaction dynamics of atoms and optical fields, but also provide an effective tool for quantum information processing. Quantum entanglement is the phenomenon which the classical theory is unable to explain, similarly non-classical effects, which is an important content in the quantum optics. The relation between entanglement and nonclassical effects is always researched.In this thesis, we investigate entanglement dynamics in cavity quantum electrodynamics (QED) system and the relation between entanglement and the nonclassical effects. The main contents of this thesis are as follows:1. By the negativity method, we investigate the entanglement dynamics of two entangled two-level atoms that go through the high Q fields in the Fock state one by one. The results shows that the two-atom initial state and the field in the Fock state are influenced on the entanglement degree of two states and the two -atom quantum state will stay in the maximum state longer when the initial condition is proper, then make the significance comparison with the two atoms’ entanglement evolutions in the condition that the two atoms are laid in QED at the same time.2. By introducing orthogonal basis, the entangled coherent states are converted to discrete ones. We calculate their entanglement by concurrence and their nonclassical effects, such as squeezing and antibunching. We find that the entanglement always follows one of squeezing and antibunching and the entanglement is increased along with the increase of one of nonclassical effects.更多还原