Decoherence by a quantum critical environment

Piotr Marecki

Bogdan Damski, H. T. Quan, Wojciech Hubert Zurek

We study decoherence induced by a dynamic environment undergoing a quantum phase transition. The environment's susceptibility to perturbations---and, consequently, the efficiency of decoherence---is amplified near a critical point. Over and above this near-critical susceptibility increase, we show that decoherence is dramatically enhanced by the nonequilibrium critical dynamics of the environment. We derive a simple expression relating decoherence to the universal critical exponents exhibiting deep connections with the theory of topological defect creation in nonequilibrium phase transitions.

Bogdan Damski, H. T. Quan, Wojciech Hubert Zurek

We study dynamics of decoherence in a generic model where the environment is driven and undergoes a quantum phase transition. We model the environment by the Ising chain in the transverse field, and assume that the decohering system is a central spin-1/2. We found that when the environment is quenched slowly through the critical point, the decoherence factor of the central spin undergoes rapid decay that encodes the critical exponents of the environment. We also found that decoherence in a non-equilibrated, kink-contaminated, environment can be stronger than in a vacuum one. We derived a remarkably simple analytical expression that describes post-transition decoherence and predicts periodicities involving all system parameters. This research connects the fields of decoherence, quantum phase transitions, and Kibble-Zurek non-equilibrium dynamics.

Bertrand Duplantier, J. M. Raimond, Vincent Rivasseau

Armando Relaño, J. M. Arias, J. Dukelsky +2 more

We analyze the decoherence induced on a single qubit by the interaction with a two-level boson system with critical internal dynamics. We explore how the decoherence process is affected by the presence of quantum phase transitions in the environment. We conclude that the dynamics of the qubit changes dramatically when the environment passes through a continuous excited state quantum phase transition. If the system-environment coupling energy equals the energy at which the environment has a critical behavior, the decoherence induced on the qubit is maximal and the fidelity tends to zero with finite size scaling obeying a power law.