# Critical points in two-channel quantum systems

## TL;DR

This paper investigates the unique features of particle transfer in two-channel open quantum systems, highlighting how singular points and coherence effects influence resonance structures and conductance, contrasting with one-channel systems.

## Contribution

It introduces a detailed analysis of two-channel quantum systems, revealing new phenomena caused by coherence and singular points not present in one-channel models.

## Key findings

- Enhanced conductance in two-channel systems due to coherence effects
- Resonance structures are affected by singular points in two-channel systems
- Phase rigidity of eigenfunctions is anti-correlated with conductance enhancements

## Abstract

Calculations for open quantum systems are performed usually by taking into account their embedding into one common environment, which is mostly the common continuum of scattering wavefunctions. Realistic quantum systems are coupled however often to more than one continuum. For example, the conductance of an open cavity needs at least two environments, namely the input and the output channel. In the present paper, we study generic features of the transfer of particles through an open quantum system coupled to two channels. We compare the results with those characteristic of a one-channel system. Of special interest is the parameter range which is influenced by singular points. Here, the states of the system are mixed via the environment. In the one-channel case, the resonance structure of the cross section is independent of the existence of singular points. In the two-channel case, however, new effects appear caused by coherence. An example is the enhanced conductance of an open cavity in a certain finite parameter range. It is anti-correlated with the phase rigidity of the eigenfunctions of the non-Hermitian Hamilton operator.