CO-MAP: A Reinforcement Learning Approach to the Qubit Allocation Problem
For quantum computing practitioners, this work significantly reduces the overhead of compiling quantum circuits for physical hardware, enabling more efficient execution.
CO-MAP formulates the qubit allocation problem as a combinatorial optimization and uses reinforcement learning to find a mapping that minimizes SWAP gate overhead, achieving a 65-85% reduction in SWAPs on MQTBench and Queko circuits compared to existing quantum compilers.
A quantum compiler is a critical piece in the quantum computing pipeline since it allows an abstract quantum circuit to be run on a physical quantum computer. One extremely important subproblem in quantum compilation is the generation of a logical to physical qubit mapping. Typically in quantum compilers this step is either implemented as a random or a heuristic based assignment that aims to minimize additional (SWAP) gate overhead in the quantum circuit. In this paper, we present an alternative approach to solving the qubit mapping problem. Specifically, we formulate the qubit mapping problem with a combinatorial optimization (CO) objective. We then present a method to find a solution to the CO problem by training a reinforcement learning (RL) policy. We also propose a local search based post-processing algorithm to further reduce the overhead. Our results show a dramatic improvement over conventional techniques in reducing the number of SWAPs. On different real world datasets like MQTBench and Queko circuits, our trained policy achieves a \textbf{65-85\%} reduction in SWAP overhead when compared to existing quantum compilers.