Quantum coherence and decoherence of protons and muons

E. Karlsson

Tyno Abdul‐Redah, M. Krzystyniak, C. A. Chatzidimitriou‐Dreismann

Walter T. Strunz

E. Karlsson

Some recent works on the tunneling of light interstitial particles (protons and positive muons) in metals are reviewed. They provide examples of simple quantum systems coupled to “baths” consisting of phonons and conduction electrons. In the limit of strong coupling to such an environment the positive muons move by quantum diffusion, where coherence is lost between each tunneling event, whereas in the weak coupling limit coherence can be maintained and allow a quantum propagation, i.e. a band-like motion. These phenomena can also be seen as examples of wave-function reduction in the presence of dissipative environments and may help to understand the details of such processes.

J. M. Wilkinson, Stephen J. Blundell

The unitary evolution of a quantum system preserves its coherence, but interactions between the system and its environment result in decoherence, a process in which the quantum information stored in the system becomes degraded. A spin-polarized positively charged muon implanted in a fluoride crystal realizes such a coherent quantum system, and the entanglement of muon and nearest-neighbor fluorine nuclear spins gives rise to an oscillatory time dependence of the muon polarization that can be detected and measured. Here we show that the decohering effect of more distant nuclear spins can be modelled quantitatively, allowing a very detailed description of the decoherence processes coupling the muon-fluorine "system" with its "environment," and allowing us to track the system entropy as the quantum information degrades. These results show how to precisely quantify the spin relaxation of muons implanted into quantum entangled states in fluoride crystals.

Gerard J. Machado