Given the characteristic function defined as: $$\chi(\beta)=\text{tr}[\rho D(\beta)],$$ with $D(\alpha)$ the displacement operator. Is it possible that for some $\rho$ we have $$\chi(\beta)=\textbf{1}_A,$$ for $\textbf{1}_A$ the indicator function of some area $A$ in phase-space?
When this characteristic function is an indicator function?
Nicolas Medina Sanchez
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