You can implement a UNet-based diffusion model for text-to-image generation using PyTorch by conditioning a denoising UNet on text embeddings through cross-attention.
Here is the code snippet below:

In the above code, we are using the following key points:
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A simplified UNet architecture for denoising
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Multihead cross-attention mechanism to condition on text embeddings
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Text embeddings are averaged and expanded to match the spatial dimensions
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Model outputs a denoised image from the noisy latent
Hence, this approach enables effective text-to-image generation by combining diffusion modeling with language-conditioned UNet architectures.