Hybrid Quantum-Classical Latent Diffusion Models for Medical Image Generation

Generative learning models in medical research are crucial in developing training data for deep learning models and advancing diagnostic tools, but the problem of high-quality, diverse images is an open topic of research. Quantum-enhanced generative models have been proposed and tested in the literature but have been restricted to small problems below the scale of industry relevance. In this paper, we propose quantum-enhanced diffusion and variational autoencoder (VAE) models and test them on the fundus retinal image generation task. In our numerical experiments, the images generated using quantum-enhanced models are of higher quality, with 86% classified as gradable by external validation compared to 69% with the classical model, and they match more closely in features to the real image distribution compared to the ones generated using classical diffusion models, even when the classical diffusion models are larger than the quantum model. Additionally, we perform noisy testing to confirm the numerical experiments, finding that quantum-enhanced diffusion model can sometimes produce higher quality images, both in terms of diversity and fidelity, when tested with quantum hardware noise. Our results indicate that quantum diffusion models on current quantum hardware are strong targets for further research on quantum utility in generative modeling for industrially relevant problems.