Simulating the out-of-equilibrium dynamics of local observables by trading entanglement for mixture. (arXiv:1810.01231v3 [cond-mat.stat-mech] UPDATED)

The fact that the computational cost of simulating a many-body quantum system
on a computer increases with the amount of entanglement has been considered as
the major bottleneck for simulating its out-of-equilibrium dynamics. Some
aspects of the dynamics are, nevertheless, robust under appropriately devised
approximations. Here we present a possible algorithm that allows to
systematically approximate the equilibration value of local operators after a
quantum quench. At the core of our proposal there is the idea to transform
entanglement between distant parts of the system into mixture, and at the same
time preserving the local reduced density matrices of the system. We benchmark
the resulting algorithm by studying quenches of quadratic Fermionic
Hamiltonians.

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