Perturbative approach for strong and weakly coupled time-dependent for non-Hermitian quantum systems

We propose a perturbative approach to determine the time-dependent Dyson map and the metric operator associated with time-dependent non-Hermitian Hamiltonians. We apply the method to a pair of explicitly time-dependent two dimensional harmonic oscillators that are weakly coupled to each other in a PT-symmetric fashion and to the strongly coupled explicitly time-dependent negative quartic anharmonic oscillator potential. We demonstrate that once the perturbative Ansatz is set up the coupled differential equations resulting order by order may be solved recursively in a constructive manner, thus bypassing the need for making any guess for the Dyson map or the metric operator. Exploring the ambiguities in the solutions of the order by order differential equations naturally leads to a whole set of inequivalent solutions for the Dyson maps and metric operators implying different physical behaviour as demonstrated for the expectation values of the time-dependent energy operator.

Automated summary

The study proposes a perturbative method to determine the time-dependent Dyson map and metric operator associated with time-dependent non-Hermitian Hamiltonians. By applying the method to different systems, it demonstrates a recursive constructive approach to solving coupled differential equations and reveals a set of inequivalent solutions for the Dyson maps and metric operators, leading to different physical behavior.