Barren plateaus in quantum neural networks, Jarrod R. McClean, Sergio Boixo, Vadim N. Smelyanskiy, Ryan Babbush, and Hartmut Neven, 2018Nature Communications, Vol. 9DOI: 10.1038/s41467-018-07090-4 - A key paper that identifies and analyzes barren plateaus, a significant training challenge for many variational quantum algorithms such as QCBMs.