Targeting Classical Code to a Quantum Annealer

Abstract

From a compiler's perspective, a quantum annealer represents a fundamentally different hardware target from a CPU, GPU, or other von Neumann architecture. Quantum annealers are special-purpose computers that use quantum effects to heuristically determine the set of Boolean variables that minimize a quadratic pseudo-Boolean function (an NP-hard problem). Natively programming such systems involves supplying them with a vector of function coefficients and receiving a vector of function-minimizing Booleans in return. The contribution of this work is to demonstrate how to compile conventional code into a minimization problem for solution on a quantum annealer. The resulting code can run either forward (from inputs to outputs) or backward (from outputs to inputs). We show how this capability can be exploited to simplify the expression and solution of problems in the NP complexity class.