Systematic nonperturbative approach to quantum nonMarkovian dynamics
Last updated March 29, 2019 by Alessandro Ferraro
Wednesday, March 27th 2019, 04:00 PM, MAPTC/0G/006
Speaker: A. Smirne (Ulm University).
I will present a general nonperturbative approach to nonMarkovian dynamics, which consists in dividing the influence of the environment on the open system into a nonMarkovian core, which encloses all the memory effects during the evolution, and a further Markovian component, representing the unidirectional leakage of information out of the nonMarkovian core. The method is built on an equivalence theorem, recently derived in [1], which proves that a Gaussian bosonic environment evolving unitarily can be replaced by a Gaussian bosonic environment undergoing a Lindblad dynamics without changing the reduced dynamics of the open system interacting with it, if the first moments and the twotime correlation functions of the original and the auxiliary baths are the same at all times. Noticeably, as a special case, one recovers the wellknown pseudomodes approach [2], directly extending it to a different form of the coupling. Starting from this result, a systematic procedure can be developed [3] to formulate auxiliary effective environments consisting of few bosonic degrees of freedom, typically a network of interacting harmonic oscillators, in this way reducing strongly the complexity of the model under study and then allowing for an efficient numerical investigation of the dynamics.
[1] D. Tamascelli, A. Smirne, S.F. Huelga, and M.B. Plenio, Nonperturbative Treatment of nonMarkovian Dynamics of Open Quantum Systems, Phys. Rev. Lett. 120, 030402 (2018).
[2] B. M. Garraway, Nonperturbative decay of an atomic system in a cavity, Phys. Rev. A 55, 2290 (1997).
[3] F. Mascherpa, A. Smirne, P. Fernandez Acebal, S. Donadi, D. Tamascelli, S.F. Huelga, and M.B. Plenio, in preparation.

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