Broad adoption of machine learning techniques has increased privacy concerns
for models trained on sensitive data such as medical records. Existing
techniques for training differentially private (DP) models give rigorous
privacy guarantees, but applying these techniques to neural networks can
severely degrade model performance. This performance reduction is an obstacle
to deploying private models in the real world. In this work, we improve the
performance of DP models by fine-tuning them through active learning on public
data. We introduce two new techniques - DIVERSEPUBLIC and NEARPRIVATE - for
doing this fine-tuning in a privacy-aware way. For the MNIST and SVHN datasets,
these techniques improve state-of-the-art accuracy for DP models while
retaining privacy guarantees.