# Symmetry-adapted variational quantum eigensolver

@article{Seki2019SymmetryadaptedVQ, title={Symmetry-adapted variational quantum eigensolver}, author={Kazuhiro Seki and Tomonori Shirakawa and Seiji Yunoki}, journal={Physical Review A}, year={2019}, volume={101}, pages={052340} }

We propose a scheme to restore spatial symmetry of Hamiltonian in the variational-quantum-eigensolver (VQE) algorithm for which the quantum circuit structures used usually break the Hamiltonian symmetry. The symmetry-adapted VQE scheme introduced here simply applies the projection operator, which is Hermitian but not unitary, to restore the spatial symmetry in a desired irreducible representation of the spatial group. The entanglement of a quantum state is still represented in a quantum circuit…

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