Out-of-time ordered correlators and entanglement growth in the random-field XX spin chain

We study out-of-time ordered correlations C(x,t) and entanglement growth in the random-field XX model with open boundary conditions using the exact Jordan-Wigner transformation to a fermionic Hamiltonian. For any nonzero strength of the random field, this model describes an Anderson insulator. Two scenarios are considered: a global quench with the initial state corresponding to a product state of the Néel form, and the behavior in a typical …