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Science 9 September 2005:
Vol. 309. no. 5741, pp. 1704 - 1707
DOI: 10.1126/science.1113479

Reports

Simulated Quantum Computation of Molecular Energies

Alán Aspuru-Guzik,1*{dagger} Anthony D. Dutoi,1* Peter J. Love,2 Martin Head-Gordon1,3

The calculation time for the energy of atoms and molecules scales exponentially with system size on a classical computer but polynomially using quantum algorithms. We demonstrate that such algorithms can be applied to problems of chemical interest using modest numbers of quantum bits. Calculations of the water and lithium hydride molecular ground-state energies have been carried out on a quantum computer simulator using a recursive phase-estimation algorithm. The recursive algorithm reduces the number of quantum bits required for the readout register from about 20 to 4. Mappings of the molecular wave function to the quantum bits are described. An adiabatic method for the preparation of a good approximate ground-state wave function is described and demonstrated for a stretched hydrogen molecule. The number of quantum bits required scales linearly with the number of basis functions, and the number of gates required grows polynomially with the number of quantum bits.

1 Department of Chemistry, University of California, Berkeley, CA, USA.
2 D-Wave Systems, Inc., 4401 Still Creek Drive, Suite 100, Burnaby, BC V5C 6G9, Canada.
3 Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: alan{at}aspuru.com

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Polynomial-time quantum algorithm for the simulation of chemical dynamics.
I. Kassal, S. P. Jordan, P. J. Love, M. Mohseni, and A. Aspuru-Guzik (2008)
PNAS 105, 18681-18686
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Science. ISSN 0036-8075 (print), 1095-9203 (online)