Nonorthogonality constraints in open quantum and wave systems
Jan Wiersig · Physical Review Research · 2019
The upper bounds for the nonorthogonality of energy eigenstates in open quantum and other wave systems are revisited. It isshown that the necessary requirements are spoiled by quantum backflow.A geometric interpretation of the nonorthogonality constraints revealsthat in this context the complex energy space can be seen as a surfaceof constant negative curvature.