Hybrid quantum-classical graph neural networks for tumor classification in digital pathology

TL;DR

This paper introduces a hybrid quantum-classical graph neural network for tumor classification in digital pathology, demonstrating comparable or improved performance over classical methods and efficient information encoding using quantum techniques.

Contribution

The study develops a novel hybrid quantum-classical GNN for tumor classification, exploring fixed and end-to-end training variants, and demonstrates quantum encoding advantages in performance and data compression.

Findings

Hybrid QNN matches classical GNN performance in key metrics.

Quantum amplitude encoding achieves better data compression and performance.

End-to-end training improves over fixed GNN parameters.

Abstract

Advances in classical machine learning and single-cell technologies have paved the way to understand interactions between disease cells and tumor microenvironments to accelerate therapeutic discovery. However, challenges in these machine learning methods and NP-hard problems in spatial Biology create an opportunity for quantum computing algorithms. We create a hybrid quantum-classical graph neural network (GNN) that combines GNN with a Variational Quantum Classifier (VQC) for classifying binary sub-tasks in breast cancer subtyping. We explore two variants of the same, the first with fixed pretrained GNN parameters and the second with end-to-end training of GNN+VQC. The results demonstrate that the hybrid quantum neural network (QNN) is at par with the state-of-the-art classical graph neural networks (GNN) in terms of weighted precision, recall and F1-score. We also show that by means of amplitude encoding, we can compress information in logarithmic number of qubits and attain better performance than using classical compression (which leads to information loss while keeping the number of qubits required constant in both regimes). Finally, we show that end-to-end training enables to improve over fixed GNN parameters and also slightly improves over vanilla GNN with same number of dimensions.