Latent Diffusion for Language Generation
Justin LovelaceVarsha KishoreChao WanEliot ShekhtmanKilian Q. Weinberger
Presents a framework that applies continuous diffusion models within the compact latent space of pretrained encoder-decoder language models, outperforming existing text diffusion methods across conditional and sequence-to-sequence generation tasks with significantly fewer sampling steps.
Diffusion models have driven major breakthroughs in generating continuous media such as images and audio, yet applying them to discrete text has proven difficult. Previous efforts attempted to replace existing language models by learning diffusion directly on individual word embeddings, but these models often suffered from training instability, degraded generation quality, and high computational costs. The article evaluates a new framework, Latent Diffusion for Language Generation (LD4LG), which demonstrates that continuous diffusion processes and pretrained language models can work complementarily rather than in competition.
The approach uses a pretrained encoder-decoder model (such as BART or FLAN-T5) paired with lightweight compression and reconstruction networks. The compression network reduces variable-length, high-dimensional text representations into a compact, fixed-size continuous latent space (reducing dimensions by a factor of 24×). A continuous diffusion model is then trained purely within this low-dimensional semantic space. During generation, the diffusion model produces a latent representation from random noise, which the pretrained decoder then translates back into natural text. The method was evaluated across multiple generation tasks using benchmark datasets, including ROCStories, AG News, Quora Question Pairs, XSum summarization, and WMT 2014 English-German translation.
The findings show that this latent diffusion framework substantially outperforms previous text diffusion methods across all evaluated tasks while requiring significantly fewer generation steps. On the ROCStories benchmark, LD4LG achieved a MAUVE quality score of 0.716 using 250 sampling steps, compared to 0.043 across 2,000 steps for Diffusion-LM. For sequence-to-sequence summarization on XSum, LD4LG scored a ROUGE-L of 31.9, more than doubling the 14.1 score of the DiffuSeq baseline. Furthermore, compared to a fine-tuned GPT-2 autoregressive model, LD4LG demonstrated substantially lower rates of training data memorization (for instance, 0.293 versus 0.829 on AG News) and showed superior steering ability in class-conditional topic generation.
These results demonstrate that separating discrete text decoding from continuous semantic planning makes diffusion viable and efficient for natural language generation. By operating in a low-dimensional latent space, the framework achieves a nearly fourfold training speedup over uncompressed diffusion baselines and reduces inference steps by roughly eightfold compared to previous text diffusion systems. This capability reduces compliance and privacy risks associated with models memorizing sensitive training data, while maintaining competitive text generation quality.
Future efforts should focus on adapting rapid sampling and model distillation techniques from the computer vision domain to reduce the required inference steps down toward single-step generation. Organizations adopting text diffusion should also explore improved re-ranking and candidate selection techniques, as optimal sample selection was shown to consistently outperform standard fine-tuned baselines. The evidence provides high confidence in the quality and memorization advantages of the latent diffusion approach, though practical deployment is currently bounded by the higher latency of iterative sampling relative to standard single-pass autoregressive decoders.
- Paper: Structured Denoising Diffusion Models in Discrete State-Spaces, Jacob Austin et al. (2021). Its discrete denoising framework establishes how diffusion can model categorical data, a foundation for understanding why this paper instead moves language generation into a continuous autoencoder latent space.
- Paper: Generating Sentences from a Continuous Space, Samuel R. Bowman et al. (2016). Its sentence-level variational autoencoder introduces continuous latent representations for text, clarifying the autoencoding step that this paper uses before applying diffusion.
- Paper: Self-conditioned Embedding Diffusion for Text Generation, Robin Strudel et al. (2022). Its continuous embedding diffusion applies denoising directly to text representations, providing a close point of comparison for this paper’s move to diffusion over learned language latents.
- Paper: Continuous diffusion for categorical data, Sander Dieleman et al. (2022). Its method adapts continuous diffusion to categorical language through token embeddings, providing a useful contrast to this paper’s pretrained autoencoder and latent-space approach.
- Paper: The Diffusion Duality, Subham Sekhar Sahoo et al. (2025). It maps continuous Gaussian diffusion to discrete text generation, extending the continuous-to-discrete bridge that this paper explores through language autoencoder latents.
- Paper: ELF: Embedded Language Flows, Keya Hu et al. (2026). Its continuous language flows denoise in embedding space and defer token conversion, carrying forward this paper’s strategy of using continuous generative modeling for language.
