Quantum fisher information transfer and distribution in a hierarchical environment

How quantum information encoded into a quantum state is lost, or transferred when an interest quantum system is coupled to its environment, is a fundamental issue in quantum information processing. In this paper, we systematically investigate the dynamics of Quantum Fisher Information (QFI) transfer and QFI flow in a hybrid quantum system composed of a three-level atom located in a cavity interacting with its own reservoir. Our analysis demonstrates that the phase (amplitude)-encoded QFI, initially localized in the atomic subsystem is completely transferred into the reservoir subsystem, as the cavity is as a bridge connecting atom to reservoir. Extending our investigation to two individual subsystems case where the QFI transfer and distribution are studied. Crucially, the relationship between the sum of the locally accessible QFI and the global QFI exhibits subadditivity, additivity, or superadditivity strongly depending on the initial entanglement configuration of the atomic states. Furthermore, the amount of information flowing from the environment (cavity plus reservoir) back into the system is also explicitly revealed by QFI flow which provides an indicator to characterizes the non-Markovianity of the open systems’ dynamics.