Connecting ansatz expressibility to gradient magnitudes and barren plateaus

@article{Holmes2021ConnectingAE,
  title={Connecting ansatz expressibility to gradient magnitudes and barren plateaus},
  author={Zoe Holmes and Kunal Sharma and Mar{\'i}a Cerezo and Patrick J. Coles},
  journal={ArXiv},
  year={2021},
  volume={abs/2101.02138}
}
Parameterized quantum circuits serve as ansätze for solving variational problems and provide a flexible paradigm for programming near-term quantum computers. Ideally, such ansätze should be highly expressive so that a close approximation of the desired solution can be accessed. On the other hand, the ansatz must also have sufficiently large gradients to allow for training. Here, we derive a fundamental relationship between these two essential properties: expressibility and trainability. This is… 

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