Subspace-search variational quantum eigensolver for excited states
Ken M. Nakanishi, Kosuke Mitarai, Keisuke Fujii · Physical Review Research · 2019
The authors propose an algorithm, the subspace-search variational quantum eigensolver (SSVQE) that searches a low energy subspace by supplying orthogonal input states to the variational ansatz and relies on the unitarity of transformations to ensure the orthogonality of output states. This work extends the applicable domain of the Variational Quantum Eigensolver to excited states and their related properties.