System susceptibility and bound-states in structured reservoirs.

Area of Science:

• Quantum Optics
• Condensed Matter Physics
• Theoretical Chemistry

Background:

• Open quantum systems are crucial for understanding energy transfer and information processing.
• Non-Markovian reservoirs introduce complex dynamics not captured by standard approximations.
• The Born-Markovian approximation simplifies these systems but often loses critical physical features.

Purpose of the Study:

• To develop an exact formulation for calculating system susceptibility in the presence of structured non-Markovian reservoirs.
• To investigate the relationship between system/reservoir bound-states and the linear response function.
• To analyze the validity of the second-order Born-Markovian approximation for open quantum systems.

Main Methods:

• Exact diagonalization of the whole-system (system plus reservoir) Hamiltonian.
• Analysis of the linear response function and its connection to bound-states and energy spectra.
• Extension of the method to general quantum networks without the rotating-wave approximation.

Main Results:

• Dissipative effects are directly linked to the structure of the non-Markovian reservoir.
• Photon bound-states and continuous energy spectra can be identified from the susceptibility.
• The Born-Markovian approximation fails to capture essential features like bound-states in open systems.

Conclusions:

• The proposed exact method provides a more accurate description of open quantum systems with structured reservoirs.
• Understanding reservoir spectral densities is key to predicting system response and bound-state phenomena.
• This work offers new insights into linear response and energy spectra in complex quantum environments.