Correlation-Picture Approach to Open-Quantum-System Dynamics

• Main Authors: S. Alipour, A. T. Rezakhani, A. P. Babu, K. Mølmer, M. Möttönen, T. Ala-Nissila
• Format: Article
• Language: English
• Published: American Physical Society 2020-11-01
• Series: Physical Review X
• Online Access: http://doi.org/10.1103/PhysRevX.10.041024

We introduce a dynamical picture, referred to as correlation picture, which connects a correlated bipartite state to its uncorrelated counterpart. This picture allows us to derive an exact dynamical equation for a general open-system dynamics with system-environment correlations included. This exact dynamics is in the form of a Lindblad-like equation even in the presence of initial system-environment correlations. For explicit calculations, we also develop a weak-correlation expansion that allows us to introduce systematic perturbative approximations. This expansion provides approximate master equations that can feature advantages over existing weak-coupling techniques. As a special case, we derive a Markovian master equation, which is different from existing approaches. We compare our equations with corresponding standard weak-coupling equations using two examples, for which our correlation-picture formalism is more accurate, or at least as accurate as the weak-coupling equations.