Coherent-State Ladder Time-Dependent Variational Principle for Open Quantum Systems

TL;DR

This paper introduces a variational method using superpositions of photon-added coherent states to efficiently simulate large, driven-dissipative many-boson open quantum systems, especially those with high occupation numbers.

Contribution

It develops a novel time-dependent variational principle based on coherent-state ladders for open quantum systems, enabling efficient simulation of complex bosonic dynamics.

Findings

Effective for large occupation number systems

Applicable to driven-dissipative and coupled modes

Demonstrated on multiple example systems

Abstract

We present a new paradigm for the dynamical simulation of interacting many-boson open quantum systems. The method relies on a variational ansatz for the $n$-boson density matrix, in terms of a superposition of photon-added coherent states. It is most efficient for the simulation of driven-dissipative systems where the state is well described by quantum fluctuations on top of a displaced field, making it suitable for the simulation of several coupled modes with large occupation numbers, that are otherwise very challenging using a Fock-space expansion. We test our method on several examples, demonstrating its potential application to the predictive simulation of interacting bosonic systems and cat qubits.