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The Jaynes–Cummings model (JCM) is a theoretical model in quantum optics. It describes the system of a two-level atom interacting with a quantized mode of an optical cavity, with or without the presence of light (in the form of a bath of electromagnetic radiation that can cause spontaneous emission and absorption). The JCM is of great interest in atomic physics, quantum optics, and solid-state quantum information circuits, both experimentally and theoretically. == History == This model was originally proposed in 1963 by Edwin Jaynes and Fred Cummings in order to study the relationship between the quantum theory of radiation and the semi-classical theory in describing the phenomenon of spontaneous emission.〔 〕 In the earlier semi-classical theory of field-atom interaction, only the atom is quantized and the field is treated as a definite function of time rather than as an operator. The semi-classical theory can explain many phenomena that are observed in modern optics, for example the existence of Rabi cycles in atomic excitation probabilities for radiation fields with sharply defined energy (narrow bandwidth). The JCM serves to find out how quantization of the radiation field affects the predictions for the evolution of the state of a two-level system in comparison with semi-classical theory of light-atom interaction. It was later discovered that the revival of the atomic population inversion after its collapse is a direct consequence of discreteness of field states (photons).〔 〕〔 〕 This is a pure quantum effect that can be described by the JCM but not with the semi-classical theory. Twenty four years later, in 1987, a beautiful demonstration of quantum collapse and revival was observed in a one-atom maser by Rempe, Walther, and Klein.〔 〕 Before that time, research groups were unable to build experimental setups capable of enhancing the coupling of an atom with a single field mode, simultaneously suppressing other modes. Experimentally, the quality factor of the cavity must be high enough to consider the dynamics of the system as equivalent to the dynamics of a single mode field. With the advent of one-atom masers it was possible to study the interaction of a single atom (usually a Rydberg atom) with a single resonant mode of the electromagnetic field in a cavity from an experimental point of view,〔 〕〔 〕 and study different aspects of the JCM. To observe strong atom-field coupling in visible light frequencies hour-glass-type optical modes can be helpful because of their large mode volume that eventually coincides with a strong field inside the cavity.〔 〕 A quantum dot inside a photonic crystal nano-cavity is also a promising system for observing collapse and revival of Rabi cycles in the visible light frequencies.〔T. Yoshie''et al.'', "Vacuum Rabi splitting with a single quantum dot in a photonic crystal nanocavity", ''Nature'' 432, 200 (2004).〕 In order to more precisely describe the interaction between an atom and a laser field, the model is generalized in different ways. Some of the generalizations are applying initial conditions,〔 〕 consideration of dissipation and damping in the model,〔〔 〕 〔 〕 consideration of multilevel atoms and multiple atoms,〔 〕 and multi-mode description of the field.〔 〕 It was also discovered that during the quiescent intervals of collapsed Rabi oscillations the atom and field exist in a macroscopic superposition state (a Schrödinger cat). This discovery offers the opportunity to use the JCM to elucidate the basic properties of quantum correlation (entanglement).〔 〕 In another work the JCM is employed to model transfer of quantum information.〔D. Ellinas and I Smyrnakis, "Asymptotics of a quantum random walk driven by an optical cavity", ''J. Opt. B'' 7, S152 (2005).〕 A more recent reference reviewing the Physics of the Jaynes-Cummings model is Journal of Physics B, 2013, vol. 46, #22, containing numerous relevant articles, including two interesting editorials, one by Cummings. The generalization of the Jaynes-Cummings model to atoms with more than two levels (equivalent to spins higher then 1/2) is known as the Dicke model or the Tavis-Cummings model. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Jaynes–Cummings model」の詳細全文を読む スポンサード リンク
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