  Nonequilibrium dynamical mean-field theory (DMFT) solves correlated lattice
models by obtaining their local correlation functions from an effective model
consisting of a single impurity in a self-consistently determined bath. The
recently developed mapping of this impurity problem from the Keldysh time
contour onto a time-dependent single-impurity Anderson model (SIAM) [C. Gramsch
et al., Phys. Rev. B 88, 235106 (2013)] allows one to use wave function-based
methods in the context of nonequilibrium DMFT. Within this mapping, long times
in the DMFT simulation become accessible by an increasing number of bath
orbitals, which requires efficient representations of the time-dependent SIAM
wave function. These can be achieved by the multiconfiguration time-dependent
Hartree (MCTDH) method and its multi-layer extensions. We find that MCTDH
outperforms exact diagonalization for large baths in which the latter approach
is still within reach and allows for the calculation of SIAMs beyond the system
size accessible by exact diagonalization. Moreover, we illustrate the
computation of the self-consistent two-time impurity Green's function within
the MCTDH second quantization representation.
