  Frustration, that is, the impossibility to satisfy the energetic preferences
between all spin pairs simultaneously, underlies the complexity of many
fundamental properties in spin systems, including the computational hardness to
determine their ground states. Coherent Ising machines (CIM) have been proposed
as a promising analog computational approach to efficiently find different
degenerate ground states of large and complex Ising models. However, CIMs also
face challenges in solving frustrated Ising models: Frustration not only
reduces the probability to find good solutions, but it also prohibits to
leverage quantum effects in doing so. To circumvent these detrimental effects
of frustration, we show how frustrated Ising models can be mapped to
frustration-free CIM configurations by including ancillary modes and modifying
the coupling protocol used in current CIM designs. In our proposal, degenerate
optical parametric oscillator (DOPO) modes encode the ground state candidates
of the studied Ising model, while the ancillary modes enable the autonomous
transformation to a frustration-free Ising model that preserves the ground
states encoded in the DOPO modes. Such frustration elimination may empower
current CIMs to improve precision and to benefit from quantum effects in
dealing with frustrated Ising models.
