Decoherence in Quantum Field Theory

Claus Kiefer

Jurjen F. Koksma, Tomislav Prokopec, Michael G. Schmidt

Charis Anastopoulos, B. L. Hu

Gravitational decoherence (GD) refers to the effects of gravity in actuating the classical appearance of a quantum system. Because the underlying processes involve issues in general relativity (GR), quantum field theory (QFT), and quantum information, GD has fundamental theoretical significance. There is a great variety of GD models, many of them involving physics that diverge from GR and/or QFT. This overview has two specific goals along with one central theme: (i) present theories of GD based on GR and QFT and explore their experimental predictions; (ii) place other theories of GD under the scrutiny of GR and QFT, and point out their theoretical differences. We also describe how GD experiments in space in the coming decades can provide evidence at two levels: (a) discriminate alternative quantum theories and non-GR theories; (b) discern whether gravity is a fundamental or an effective theory.

Hao Xu, Si Yu Chen, Yen Chin Ong

Abstract We consider quantum decoherence and Landauer’s principle in qubit-cavity quantum field theory (QFT) interaction, treating the qubit as the system and cavity QFT as the environment. In particular, we investigate the changes that occur in the system with a pure initial state and environment during the decoherence process, with or without energy dissipation, and compare the results with the case in which the initial state of the system is a mixed state and thus decoherence is absent. When we choose an interaction Hamiltonian such that the energy and coherence of the system change simultaneously, the population change of the system and the energy change are the same when the initial state is mixed. However, the decoherence terms increase the von Neumann entropy of the system. In this case the energy change and decoherence of the system are not independent physical processes. The decoherence process maintains unitarity. On the other hand, if the interaction Hamiltonian does not change the energy of the system, there is only the decoherence effect. The environment will be a distribution in the basis of the displaced number state and always increases the energy. Landauer’s principle is satisfied in both cases.

Walter T. Strunz

Jincheng Zhang

This paper presents a comprehensive model for quantum decoherence, grounded in the principles of quantum field theory (QFT) and statistical mechanics. The core argument is that traditional decoherence models often oversimplify the process, failing to adequately capture the intricate interactions arising from the quantum effects of the surrounding environment. This work introduces a framework that explicitly incorporates the scattering of quantum states by the environment, treated as a QFT system, and then analyzes the resultant impact using statistical mechanics. The model aims to provide a more accurate and nuanced understanding of decoherence, particularly in scenarios involving strong environmental interactions. Specifically, the model utilizes the formalism of quantum scattering theory to describe the interaction between a quantum system and its environment. The resulting dynamics are then analyzed using the framework of statistical mechanics, allowing for the calculation of decoherence rates as a function of environmental parameters such as temperature and density. The key contributions of this work include a detailed mathematical description of the decoherence process, a clear separation of the quantum and classical aspects of the problem, and a framework for extending the model to more complex systems. The model predicts that decoherence is not simply a loss of quantum information, but rather a fundamental process of state transformation driven by the statistical properties of the environment. This work offers a significant step forward in our ability to understand and potentially mitigate the effects of decoherence in quantum technologies.