A variational eigenvalue solver on a photonic quantum processor

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

Research output: Contribution to journalArticlepeer-review

1574 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 ansätze 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
JournalNature Communications
Publication statusPublished - 23 Jul 2014


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