  Reconfigurable antenna multiple-input multiple-output (MIMO) is a promising
technology for upcoming 6G communication systems. In this paper, we deal with
the problem of configuration selection for reconfigurable antenna MIMO by
leveraging Coherent Ising Machines (CIMs). By adopting the CIM as a heuristic
solver for the Ising problem, the optimal antenna configuration that maximizes
the received signal-to-noise ratio is investigated. A mathematical framework
that converts the selection problem into a CIM-compatible unconstrained
quadratic formulation is presented. Numerical studies show that the proposed
CIM-based design outperforms classical counterparts and achieves near-optimal
performance (similar to exponentially complex exhaustive searching) while
ensuring polynomial complexity.
