A variational eigenvalue solver on a photonic quantum processor

Alberto Peruzzo*, Jarrod McClean, Peter Shadbolt, Man-Hong Yung, Xiao-Qi Zhou, Peter J. Love, Alan Aspuru-Guzik, Jeremy L. O'Brien

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

2306 Citations (Scopus)


Quantum computers promise to efficiently solve important problems that are intractable on a conventional computer. For quantum systems, where the physical dimension grows exponentially, finding the eigenvalues of certain operators is one such intractable problem and remains a fundamental challenge. The quantum phase estimation algorithm efficiently finds the eigenvalue of a given eigenvector but requires fully coherent evolution. Here we present an alternative approach that greatly reduces the requirements for coherent evolution and combine this method with a new approach to state preparation based on ansatze and classical optimization. We implement the algorithm by combining a highly reconfigurable photonic quantum processor with a conventional computer. We experimentally demonstrate the feasibility of this approach with an example from quantum chemistry-calculating the ground-state molecular energy for He-H+. The proposed approach drastically reduces the coherence time requirements, enhancing the potential of quantum resources available today and in the near future.

Original languageEnglish
Article number4213
Number of pages7
JournalNature Communications
Publication statusPublished - 23 Jul 2014

Structured keywords

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