p-bits: a probabilistic AND gate that also runs backwards  (Datta Part B, Ch. 25, Eqs. 25.6)

Each node is a three-terminal p-bit: V_i = sgn[ tanh(I₀ν_i) + rand(−1,+1) ] with input ν_i = Σ_j J_ijV_j + h_i. With J_AB=−1, J_AC=J_BC=2 and h=(1,1,−2) the network spends its time in the four rows of the AND truth table (C = A AND B). Clamp C = 1 and the inputs are forced to A = B = 1: inversion.