چكيده لاتين
Quantum coherent superposition and its many-particle example, entanglement, are two fundamental aspects of quantum mechanics that describe the behavior of physical systems quantum mechanically. Quantum entanglement, due to its remarkable properties, plays a unique role in quantum information processing protocols. However, the irreversible decay of quantum coherence, known as decoherence, which arises inevitably from the coupling of physical systems with their surrounding environment, poses a major challenge to the realization of quantum information processing protocols. Therefore, achieving a deep understanding of the mechanism of quantum decoherence not only aids in comprehending fundamental issues such as the classical limit of quantum mechanics and measurement theory, but also holds special importance because quantum information processing and various quantum technologies fundamentally depend on the generation, stabilization, and manipulation of quantum coherent superposition states.
In this thesis, we investigate the effect of decoherence arising from the interaction between a system and its environment. In this study, physical systems are modeled as the main subsystem, while the surrounding environment, with infinitely many degrees of freedom, is treated as an irrelevant subsystem. However, this modeling can be generalized to environments with a finite number of degrees of freedom. Initially, fundamental concepts are defined to advance the objectives. Next, the basic form of decoherence is derived, and alongside its formal expression, its connection to indirect measurement is discussed. The Markovian master equation is also employed to gain a fundamental understanding of decoherence. Subsequently, the effects of quantum states, phase properties of the intracavity radiation field, and the back-action of spontaneously emitted photons on the spatial decoherence of the center-of-mass motion of a single atom in a closed wave space are examined. Then, various aspects of decoherence effects resulting from the motion of a single atom (decoherence due to the atomʹs external degrees of freedom) on the dynamics of the single-atom-cavity field interaction system are studied, with a particular focus on the decoherence dynamics of quantum correlations between the internal degree of freedom of the single atom and the field. Fundamental aspects of which-path information and quantum erasure are also explored in this part. Finally, the effect of atomic motion on the entanglement dynamics between the internal degrees of freedom of two moving atoms is analyzed, along with the study of spatial decoherence dynamics in systems composed of two moving atoms and the impact of back-action from spontaneous emission on the relative position entanglement of the two atoms.
