Sthitadhi Roy, Tanay Nag, Amit Dutta
We study the non-equilibrium dynamics of a one-dimensional system of hard core bosons in the presence of an onsite potential (with an alternating sign between the odd and even sites) which shows a quantum phase transition from the superfluid (SF) phase to the Mott Insulator (MI) phase. The ground state quantum fidelity shows a sharp dip at the QCP while the fidelity susceptibility shows a divergence right there with its scaling given in terms of the correlation length exponent of the quantum phase transition. We then study the evolution of this bosonic system (with a qubit globally coupled to it) following a quench in which the magnitude of the alternating potential is changed from zero (the SF phase) to a non-zero value (the MI phase) according to a half Rosen Zener scheme. The loss of coherence of the qubit (initially in a pure state) after the quench is investigated by calculating the time dependence of the decoherence factor. This result is compared with that of the sudden quench limit of the half Rosen-Zener scheme where an exact analytical form of the decoherence factor can be derived. The local von Neumann entropy density is calculated in the final MI phase and is found to be less than the equilibrium value ($\log 2$) due to the defects generated in the final state as a result of the quenching that starts from the QCP of the system. We also briefly dwell on the full Rosen-Zener quenching scheme in which the system is finally brought back to the SF phase through the intermediate MI phase and calculate the reduction in the supercurrent and the non-zero value of the residual local entropy density in the final state.
View original:
http://arxiv.org/abs/1212.4655
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