Abstract
Like the progress made by Dirac that wave function ψ (x) was reformed as <x |ψ>, where <x| is the coordinate representation, we endow the characteristic function χ λ = \( Tr(e^{\lambda a^\dag - \lambda ^* a} \rho ) \) of density operator ρ with the meaning of wave function of |ρ> in the thermal entangled state <η| representation in the doubled Fock space, χ λ = <η = −λ|ρ>, where |ρ> = ρ|η = 0>. We find the time evolution of χ λ can then be directly and neatly obtained via this approach. The way of deriving the density operator from <η = −λ | ρ> is also presented.
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Chen, F., Fan, H. A new approach to the time evolution of characteristic function of the density operator obtained by virtue of thermal entangled state representation. Sci. China Phys. Mech. Astron. 55, 2076–2080 (2012). https://doi.org/10.1007/s11433-012-4893-4
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DOI: https://doi.org/10.1007/s11433-012-4893-4