Dynamics and steady state properties of quantum correlations in periodically driven Ising spin chain

Speaker: Utkarsh Mishra
Title: Dynamics and steady state properties of quantum correlations in periodically driven Ising spin chain
Time: 3:00pm—5:00pm, April.24.2018 
Location: 818 Conference Room, Communication Building, Shahe Campus


Dr Utkarsh Mishra obtained his PhD degree from Harish-Chandra Research Institute, India, in the field of Physics. He is currently working as a postdoctoral research fellow at Asia Pacific Center for Theoretical Physics at Pohang, South Korea. His major areas of research includes: Quantum Information; Many-Body Theory &Many-Body Theory and Correlated Systems Group.


We study the dynamics of microscopic quantum correlations, viz., bipartite entanglement and quantum discord, in Ising spin chain with periodically varying external magnetic field along the transverse direction. Depending upon the system parameters, local quantum correlations in the evolved states of such systems may get saturated to non-zero values after sufficiently large number of driving cycles. Moreover, we investigate convergence of the local density matrices, from which the quantum correlations under study originate, towards the final steady-state density matrices as a function of driving cycles. We find that the geometric distance between the non-equilibrium and the steady-state reduced density matrices obey power-law scaling. The steady-state quantum correlations corresponding to various initial states in thermal equilibrium are studied as a function of drive time period of a square pulsed field. The steady-state quantum correlations are marked by presence of peaks in the frequency domain. The steady-state features can be furtherunderstood by probing band structures of Floquet Hamiltonian. Finally, we compare the steady state values of the local quantum correlations under study with that of the canonical Gibbs ensemble and infer about the canonical ergodic properties. We find that depending upon the quantum phases of the initial state and the pathway of the driving Hamiltonian the final values of the long-time quantum correlations may correspond to a canonical Gibbs state. We also find parameter regimes where this correspondence does not hold.