Absorbers as detectors for unbound quantum systems

Abstract

Complex absorbing potentials are frequently employed in quantum calculations. One of the advantages that such absorbers provide is the ability to attenuate outgoing waves in simulations of unbound systems, thus allowing for truncating the numerical domain. Here we argue that the absorber may also be used to probe outgoing waves so that physical information about absorbed particles may be retained. Moreover, under certain conditions, the physical information extracted via the absorber is subject to loss in coherence, as is also the case when collapsing the wave function upon measurement. Both these aspects demonstrate clearly how, and when, the effect of introducing a complex absorbing potential corresponds to that of a detector.