Fast quantum many-body state preparation using non-Gaussian variational ansatz and quantum optimal control

We show how to exploit a variational ansatz based on non-Gaussian wavefunctions for fast non-adiabatic preparation of quantum many-body states using quantum optimal control. We demonstrate this on the example of spin-boson model, where we determine the optimal time variation of the Hamiltonian parameters to prepare (near) critical ground states in times, which clearly outperform optimized adiabatic protocols. To this end we use the time dependent variational principle and polaron-like ansatz states, which correspond to generalized many-body squeezed cat states of the bosonic modes coupled to the spin.