Reduced-density matrix Quantum theory 14 Matrix algebra 10 External environments 6 reduced density matrix 6 Computational costs 4 Configuration interactions 4 Correlation detectors 4 Dinger equation 4 G-particle-hole matrix 4 Geometric phase 4 Geometry 4 Ground state 4 Quantum chemistry 4 Quantum entanglement 4 Two-level system 4 contracted Schrödinger equation 4 correlation matrix 4 electronic correlation effects 4 hypervirial of the G-particle-hole matrix 4 Analytical model 2 Bipartite state 2 Bipartite systems 2 Composite environment 2 Composite systems 2 Computation theory 2 Computational efficiency 2 Configuration interaction method 2 Correlated wave functions 2 Correlation matrix 2