  We demonstrate a spin-wave-based time-multiplexed Ising Machine (SWIM),
implemented using a 5 $\mu$m thick Yttrium Iron Garnet (YIG) film and
off-the-shelf microwave components. The artificial Ising spins consist of
34--68 ns long 3.125 GHz spinwave RF pulses with their phase binarized using a
phase-sensitive microwave amplifier. Thanks to the very low spinwave group
velocity, the 7 mm long YIG waveguide can host an 8-spin MAX-CUT problem and
solve it in less than 4 $\mu$s while consuming only 7 $\mu$J. Using a real-time
oscilloscope, we follow the temporal evolution of each spin as the SWIM
minimizes its energy and find both uniform and domain-propagation-like
switching of the spin state. The SWIM has the potential for substantial further
miniaturization, scalability, speed, and reduced power consumption, and may
become a versatile platform for commercially feasible optimization problem
solvers with high performance.
