熱浴と接触する系に対する非平衡Thermo Field Dynamicsと射影演算子法

B. Picinbono, M. Rousseau

Stationary Gaussian optical fields are also often called thermal fields because they are generated by natural or thermal sources. By using the amplitude of the field, we show that thermal fields are only a particular case of the more general class of Gaussian fields. Such nonthermal Gaussian fields can be obtained experimentally, and we calculate some properties, concerning particularly the effect of Hanbury Brown and Twiss, photocounting, and coincidence experiments. We show that the thermal fields are the less chaotic or incoherent Gaussian fields. Finally, we introduce pseudo-Gaussian fields which appear in some experiments of diffusion with laser light. They are non-Gaussian fields, but their intensity has the same properties as that of a Gaussian field.

祐介 中村, 知夏 須永, 真如 峰 +2 more

中村 祐介, 山田 由也

Jia Jin-ping

The property of the field entropy in degenerate Raman coupling Jaynes-Jummings models with a linear time-dependent atom-field coupling is investigated.The influence of different initial field and time-dependent atom-field coupling coefficient on the field entropy is discussed at length.The results show that:(1) All the evolutions of field entropies have periodicity whatever the initial field states are.The increase of the mean number of photon does not change evolution periodicity;(2) The different statistical properties of the initial fields will give great effects on the values of the maximum field entropy and the variational range the highest value of field entropy;(3) the perfect periodicity of field entropy will be destroyed due to the linear modulation.When the atom-field coupling coefficient changes slowly,the speed of atoms′ entering the statistical state is slowered;when the atomfield coupling coefficient changes rapidly,the oscillating periodicity of the curve of the evolution of field entropy is shortened,the oscillating frequency of the evolution of field entropy is fastened,and the moments of the atom-field disentanglement are manifolded.

刘小娟 LIU Xiaojuan, 刘一曼 LIU Yi-man, 刘敏 Liu Min

In the rotating-wave approximation,the evolution of the field quantum entropy in the system that consists of a two-level atom interacting with a single-mode field was studied,considering the atomic motion and the field frequency varying with the time in the form of sine-function at the same time.In two cases of neglecting atomic motion and considering atomic motion,figures of the time evolutions of the field entropy were plotted respectively using numerical calculations.Influences of the atomic motion,the field-model structure parameter,amplitude and angular frequency of the field-frequency variation on the field entropy were also discussed.The atom-field entangled states,field fock states and atomic high fidelity states were prepared by analytic method according to the decomposition theorem of Schmidt,and the related system parameters of these quantum states operation were acquired.The results show that:the time evolution behavior of the field entropy is modulated by the frequency variation of field;the interaction between the field and atom will weaken with the increase of the amplitude of variation of the field frequency;the period of the field entropy agrees with the period of field-frequency variation;the atomic motion will result in the period of the field entropy doubled;the evolution of the field entropy is related to the parity of field-mode structure parameter;the approximate EPR states of field-atom can be prepared periodically whether the atom moves or not.

Saito, Takeshi, 敏彦 有光