1. Theorie

Taming the dynamical sign problem: the Inchworm algorithm

by Prof. Guy Cohen, Tel Aviv University

Friday, 13 October 2017 from to (Europe/Berlin)
at Jungiusstr. 9 ( Room 222 )

Nonequilibrium Monte Carlo methods suffer from a dynamical sign problem that
makes simulating real-time dynamics for long times exponentially hard. A new
“Inchworm Algorithm”, based on iteratively reusing information obtained in
previous steps to extend the propagation to longer times, largely overcomes the
dynamical sign problem. This changes the scaling from exponential to quadratic
in a wide range of strongly correlated physical regimes. The method has so far
been applied to the Anderson impurity model and to the spin–boson model. We
present results including quench dynamics; response to time-dependent fields;
real-time Green’s functions; and, most recently, full counting statistics.

1. G. Cohen, E. Gull, D.R. Reichman, A.J. Millis, “Taming the dynamical sign
problem in real-time evolution of quantum many-body problems”, Phys. Rev. Lett.
115, 266802 (2015)

2. H.T. Chen, G. Cohen, D.R. Reichman, “Inchworm Monte Carlo for exact
non-adiabatic dynamics I. Theory and algorithms”, J. Chem. Phys. 146, 05410

3. A.E. Antipov, Q. Dong, J. Kleinhenz, G. Cohen, E. Gull, “Currents and
Green’s functions of impurities out of equilibrium: results from inchworm
Quantum Monte Carlo”, Phys. Rev. B 95, 085144 (2017)

4 Q. Dong, I. Krivenko, J. Kleinhenz, A.E. Antipov, G. Cohen, E. Gull, “Quantum 
Monte Carlo solution of the dynamical mean field equations in real time”,