A Multireference Quantum Krylov Algorithm for Strongly Correlated Electrons

Understand

We introduce a multireference selected quantum Krylov (MRSQK) algorithm suitable for quantum simulation of many-body problems.

• MRSQK is a low-cost alternative to the quantum phase estimation algorithm that generates a target state as a linear combination of non-orthogonal Krylov basis states.
• This basis is constructed from a set of reference states via real-time evolution avoiding the numerical optimization of parameters.
• An efficient algorithm for the evaluation of the off-diagonal matrix elements of the overlap and Hamiltonian matrices is discussed and a selection procedure is introduced to identify a basis of orthogonal references that ameliorates the linear dependency problem.