ffsim.linalg.reduced_matrix¶

ffsim.linalg.reduced_matrix(mat, vecs)[source]¶

Compute reduced matrix within a subspace spanned by some vectors.

Given a linear operator \(A\) and a list of vectors \(\{v_i\}\), return the matrix M where \(M_{ij} = v_i^\dagger A v_j\).