Optimal preparation of the maximally entangled W state of three superconducting gmon qubits

Abstract: Superconducting gmon qubits allow for highly tuneable quantum computing devices. Optimally controlled evolution of these systems is of considerable interest. We determine the optimal dynamical protocols for the generation of the maximally entangled W state of three qubits from an easily prepared initial product state. These solutions are found by simulated annealing. Using the connection to the Pontryagin's minimum principle, we fully characterize the patterns of these ``bang-bang'' protocols, which shortcut the adiabatic evolution. The protocols are remarkably robust, facilitating the development of high-performance three-qubit quantum gates.