In this paper we derive an exact master equation for two coupled quantum harmonic oscillators interacting via bilinear coupling with a common environment at arbitrary temperature made up of many harmonic oscillators with a general spectral density function. We first show a simple derivation based on the observation that the two-harmonic oscillator model can be effectively mapped into that of a single harmonic oscillator in a general environment plus a free harmonic oscillator. Since the exact one harmonic oscillator master equation is available [Hu, Paz and Zhang, Phys. Rev. D 45, 2843 (1992)], the exact master equation with all its coefficients for this two harmonic oscillator model can be easily deduced from the known results of the single harmonic oscillator case. In the second part we give an influence functional treatment of this model and provide explicit expressions for the evolutionary operator of the reduced density matrix which are useful for the study of decoherence and disentanglement issues. We show three applications of this master equation: on the decoherence and disentanglement of two harmonic oscillators due to their interaction with a common environment under Markovian approximation, and a derivation of the uncertainty principle at finite temperature for a composite object, modeled by two interacting harmonic oscillators. The exact master equation for two, and its generalization to N , harmonic oscillators interacting with a general environment are expected to be useful for the analysis of quantum coherence, entanglement, fluctuations and dissipation of mesoscopic objects towards the construction of a theoretical framework for macroscopic quantum phenomena.
Novel ter(9,9-diarylfluorene)s were synthesized by a Suzuki-coupling reaction of 2-bromofluorene (1) and 2,7-fluorenediboronic ester derivatives (3) with high isolated yields (63-86%). The X-ray structure analysis of ter(9,9'-spirobifluorene) (4aa) revealed that the conjugated chromophore adopts a helical conformation. This conformation effectively releases the steric interaction between the fluorene moieties and prevents inter-chromophore interactions. The introduction of aryl groups at the C9 position of fluorene was highly beneficial to the thermal and morphological stability of these oligomers. These terfluorenes exhibit intense blue fluorescence with excellent quantum yields both in solution ( approximately 100%) and in solid state (66-90%), and possess interesting reversible redox properties. Highly efficient blue light-emitting OLED devices were fabricated using 4aa and 4cc as emitters as well as hole transporters. The devices exhibit low turn-on voltage ( approximately 3 V) and high EL external quantum efficiency (2.5-3%).
We study the dynamics of quantum entanglement between two Unruh-DeWitt detectors, one stationary (Alice), and another uniformly accelerating (Rob), with no direct interaction but coupled to a common quantum field in (3+1)D Minkowski space. We find that for all cases studied the initial entanglement between the detectors disappears in a finite time ("sudden death"). After the moment of total disentanglement the correlations between the two detectors remain nonzero until late times. The relation between the disentanglement time and Rob's proper acceleration is observer dependent. The larger the acceleration is, the longer the disentanglement time in Alice's coordinate, but the shorter in Rob's coordinate.Comment: 16 pages, 8 figures; typos added, minor changes in Secs. I and
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