Information and decoherence in muon-fluorine coupled systems*

Quantum systems remain coherent due to their unitary time evolution. However, when a subsystem interacts with the rest of the system (the environment) then interactions can result in a degrading of the quantum information in the subsystem. This situation is realised when a spin-polarised positive muon is implanted in a fluoride crystal. We have developed a method [1] to model this problem and account for our experimental data in a variety of fluorides without resorting to phenomenological stretched exponential functions that have been used in most previous treatments. These new ideas shed light on the muon site problem and provide some new insights into the process of decoherence in spin systems. [1] J. M. Wilkinson and S. J. Blundell, Phys. Rev. Lett. 125, 087201 (2020).