Quantum dynamical arrest and release in anistropic dipolar magnets

In this talk I will discuss the dynamics of LiHo x Y 1 x F 4 in the presence of an applied transverse field We calculated the dynamics between the doublet Ising levels in the framework of the two Ho ions Hamiltonian accounting for the existence of Quantum Dynamical Arrest QDA followed by Quantum Dynamical Release QDR The mechanism of the QDA and QDR will be discussed and compared to a similar mechanism recently suggested for structural glasses