  The electronic structure problem is one of the main problems in modern
theoretical chemistry. While there are many already-established methods both
for the problem itself and its applications like semi-classical or quantum
dynamics, it remains a computationally demanding task, effectively limiting the
size of solved problems. Fortunately, it seems, that offloading some parts of
the computation to Quantum Processing Units may offer significant speed-up,
often referred to as quantum supremacy or quantum advantage. Together with the
potential advantage, this approach simultaneously presents several problems,
most notably naturally occurring quantum decoherence, hereafter denoted as
quantum noise and lack of large-scale quantum computers, making it necessary to
focus on Noisy-Intermediate Scale Quantum computers when developing algorithms
aspiring to near-term applications. SA-OO-VQE package aims to answer both these
problems with its hybrid quantum-classical conception based on a typical
Variational Quantum Eigensolver approach, as only a part of the algorithm
utilizes offload to QPUs and the rest is performed on a classical computer,
thus partially avoiding both quantum noise and the lack of quantum bits. The
SA-OO-VQE has the ability to treat degenerate (or quasi-degenerate) states on
the same footing, thus avoiding known numerical optimization problems arising
in state-specific approaches around avoided crossings or conical intersections.
