The theory of variational hybrid quantum-classical algorithms

@article{McClean2015TheTO,
  title={The theory of variational hybrid quantum-classical algorithms},
  author={Jarrod R. McClean and Jonathan Romero and Ryan Babbush and Al{\'a}n Aspuru-Guzik},
  journal={New Journal of Physics},
  year={2015},
  volume={18},
  pages={023023}
}
Many quantum algorithms have daunting resource requirements when compared to what is available today. To address this discrepancy, a quantum-classical hybrid optimization scheme known as 'the quantum variational eigensolver' was developed (Peruzzo et al 2014 Nat. Commun. 5 4213) with the philosophy that even minimal quantum resources could be made useful when used in conjunction with classical routines. In this work we extend the general theory of this algorithm and suggest algorithmic… 
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