Fig. 2: Experimental demonstration of 4-spin SWIM solving a MAX-CUT problem.
From: A spinwave Ising machine
a, b Transformation of the initial non-optimal state (a) to an optimal solution (b) for 4-spin MAX-CUT optimization problem. The number of cuts for the MAX-CUT problem is determined by the total number of couplings that cross the line separating the spins into two groups, considering their regrouping based on their spin values. c An optimal solution for 8-spin MAX-CUT optimization problem with eight cuts. SWIM control traces for 4-spin (d, e) and 8-spin (f) problems. Amplified signals of RF propagating pulses in the initial non-optimal state (g) of MAX-CUT 4-spin and the final solutions of MAX-CUT 4-spin problem (h) and 8-spin problem (i). A control signal of switch 3 has a repetition frequency of fswitch = 14.8 MHz (d, e) for 4-spin problem and 29.6 MHz (f) for 8-spin problem and duty cycle of 50% that forms oscillations in the SWIM ring oscillator into separate propagating RF pulses. Calculated instantaneous phase signals for 4-spin problem (j, k) and 8-spin problem (l). The time traces in (g–i) are colored according to a value of the calculated instantaneous signal to visually show the pulse instantaneous phase. Since the time intervals shown are much longer than the oscillation period of the propagating pulses Vampl (1/3.125 GHz = 0.320 ns), individual oscillations are not resolved and merge into a colored continuum.
