From the state diagram one can infer that Qn+1 = Qn, when x = y, and Qn+1 = Q'n, when x != y
For JK flip flop Qn+1 = Qn, if J=K=0 and
Qn+1 = Q'n , if J=K=1
and as EX-OR gate is non-equivalence gate it satisfies for the above conditions of J and K when X and Y are taken as inputs.