  Diabatic quantum annealing (DQA) is an alternative algorithm to adiabatic
quantum annealing (AQA) that can be used to circumvent the exponential slowdown
caused by small minima in the annealing energy spectrum. We present the locally
suppressed transverse-field (LSTF) protocol, a heuristic method for making
stoquastic optimization problems compatible with DQA. We show that, provided an
optimization problem intrinsically has magnetic frustration due to
inhomogeneous local fields, a target qubit in the problem can always be
manipulated to create a double minimum in the energy gap between the ground and
first excited states during the evolution of the algorithm. Such a double
energy minimum can be exploited to induce diabatic transitions to the first
excited state and back to the ground state. In addition to its relevance to
classical and quantum algorithmic speed-ups, the LSTF protocol enables DQA
proof-of-principle and physics experiments to be performed on existing
hardware, provided independent controls exist for the transverse qubit
magnetization fields. We discuss the implications on the coherence requirements
of the quantum annealing hardware when using the LSTF protocol, considering
specifically the cases of relaxation and dephasing. We show that the relaxation
rate of a large system can be made to depend only on the target qubit
presenting new opportunities for the characterization of the decohering
environment in a quantum annealing processor.
