Emergence of distinct relaxation behaviour and Quantum Regression Theorem in the Ultra-strong Coupling Limit
- URL: http://arxiv.org/abs/2508.08378v1
- Date: Mon, 11 Aug 2025 18:04:02 GMT
- Title: Emergence of distinct relaxation behaviour and Quantum Regression Theorem in the Ultra-strong Coupling Limit
- Authors: Sakil Khan, Bijay Kumar Agarwalla,
- Abstract summary: We derive the dynamical equation governing two-time correlation functions in open quantum systems.<n>We find distinct relaxation behavior for two-time correlators depending on the types of the operators involved in the correlation function.
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- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: In the framework of open quantum systems, we derive the dynamical equation governing two-time correlation functions in the ultra-strong coupling (USC) regime between the system and its environment. Unlike the case of the standard weak-coupling regime, in the USC case, we find distinct relaxation behavior for two-time correlators depending on the types of the operators involved in the correlation function. Interestingly, the Quantum Regression Theorem (QRT) emerges after the fastest relaxation time-scale, which is governed by the system-bath coupling strength. We exemplify our findings for the dissipative spin-boson model and further find excellent agreement with the numerically exact hierarchical equations of motion (HEOM) method.
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