Efficient Numerical Optimal Control for Ground-State Reset of Open Quantum Systems

This paper presents a numerical optimization framework for solving the ground state reset problem where a number of qubits are dispersively coupled to a readout cavity. We model the open system quantum dynamics using Lindblad's master equation, driven by external control pulses. We develop a basis of density matrices (a parameterization) where each basis element is a density matrix itself. Together with a new objective function, we show how a superposition of the basis elements can be used in such a way that the objective function can be evaluated by solving the master equation for one initial condition only - independent of the system dimension. This enables efficient ground state reset allowing for an increasing number of qubits. Numerical results demonstrate efficient optimal control for ground-state reset of one and two qubits coupled to a readout cavity.