  Diffusion models have achieved great success in modeling continuous data
modalities such as images, audio, and video, but have seen limited use in
discrete domains such as language. Recent attempts to adapt diffusion to
language have presented diffusion as an alternative to existing pretrained
language models. We view diffusion and existing language models as
complementary. We demonstrate that encoder-decoder language models can be
utilized to efficiently learn high-quality language autoencoders. We then
demonstrate that continuous diffusion models can be learned in the latent space
of the language autoencoder, enabling us to sample continuous latent
representations that can be decoded into natural language with the pretrained
decoder. We validate the effectiveness of our approach for unconditional,
class-conditional, and sequence-to-sequence language generation. We demonstrate
across multiple diverse data sets that our latent language diffusion models are
significantly more effective than previous diffusion language models.
