Pure state vs. density matrix approaches for non-Markovian open quantum systems

To efficiently treat non-Markovian open quantum systems is a challenging task. One often used approach, denoted as HEOM [1], is using a hierarchy of coupled operator equations.

In this contribution we compare the recently developed hierarchy of pure states (HOPS) [2], which is a stochastic method, with the corresponding hierarchy of operators. We find in particular that in general HOPS requires much less numerical resources than HEOM.

[1] Y. Tanimura; J Phys. Soc. Japan 75 082001
[2] D. Suess et al; phys. Rev. Lett. 113 150402