Stoquastic

Stoquastic Hamiltonians, those for which all off-diagonal matrix elements in the standard basis are real and non-positive, are common in the physical world.

We contrast this with the case of sampling from the output of a quantum computer running the Quantum Adiabatic Algorithm (QADI) with the restriction that the Hamiltonian that governs the evolution is gapped and stoquastic.

As stoquastic problems we use frustrated Ising Hamiltonians, having random local X and Z fields, and random σ_zσ_z couplings.