DDPM:Lower bound of logP(x) VAE Maximize logPa(x) Maximize☑[log P(,Z q☑x) Encoder DDPM Maximize logPe(xo) Maximize q(x log P(xo:xT q(x:xrlxo) Forward Process (Diffusion Process) q(x1:xTlxo)=q(xilxo)q(x21x1)...q(xrlxT-1)DDPM: Lower bound of 𝑙𝑜𝑔𝑃 𝑥 Maximize 𝑙𝑜𝑔𝑃𝜃 𝑥0 Maximize E𝑞 𝑥1:𝑥𝑇|𝑥0 [𝑙𝑜𝑔 𝑃 𝑥0: 𝑥𝑇 𝑞 𝑥1: 𝑥𝑇|𝑥0 ] Maximize 𝑙𝑜𝑔𝑃𝜃 𝑥 Maximize E𝑞 𝑧|𝑥 [𝑙𝑜𝑔 𝑃 𝑥, 𝑧 𝑞 𝑧|𝑥 ] Encoder Forward Process (Diffusion Process) VAE DDPM 𝑞 𝑥1: 𝑥𝑇|𝑥0 = 𝑞 𝑥1|𝑥0 𝑞 𝑥2|𝑥1 … 𝑞 𝑥𝑇|𝑥𝑇−1