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Title: Computation of Molecular Spectra on a Quantum Processor with an Error-Resilient Algorithm

Harnessing the full power of nascent quantum processors requires the efficient management of a limited number of quantum bits with finite coherent lifetimes. Hybrid algorithms, such as the variational quantum eigensolver (VQE), leverage classical resources to reduce the required number of quantum gates. Experimental demonstrations of VQE have resulted in calculation of Hamiltonian ground states, and a new theoretical approach based on a quantum subspace expansion (QSE) has outlined a procedure for determining excited states that are central to dynamical processes. Here, we use a superconducting-qubit-based processor to apply the QSE approach to the H 2 molecule, extracting both ground and excited states without the need for auxiliary qubits or additional minimization. Further, we show that this extended protocol can mitigate the effects of incoherent errors, potentially enabling larger-scale quantum simulations without the need for complex error-correction techniques.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [2] ;  [3]
  1. Univ. of California, Berkeley, CA (United States). Quantum Nanoelectronics Lab., Dept. of Physics
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Computational Research Division
  3. Univ. of California, Berkeley, CA (United States). Quantum Nanoelectronics Lab., Dept. of Physics; Univ. of California, Berkeley, CA (United States). Center for Quantum Coherent Science; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Published Article
Journal Name:
Physical Review. X
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Related Information: © 2018 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.; Journal ID: ISSN 2160-3308
Publisher:
American Physical Society
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1420209
Alternate Identifier(s):
OSTI ID: 1434014

Colless, J. I., Ramasesh, V. V., Dahlen, D., Blok, M. S., Kimchi-Schwartz, M. E., McClean, J. R., Carter, J., de Jong, W. A., and Siddiqi, I.. Computation of Molecular Spectra on a Quantum Processor with an Error-Resilient Algorithm. United States: N. p., Web. doi:10.1103/PhysRevX.8.011021.
Colless, J. I., Ramasesh, V. V., Dahlen, D., Blok, M. S., Kimchi-Schwartz, M. E., McClean, J. R., Carter, J., de Jong, W. A., & Siddiqi, I.. Computation of Molecular Spectra on a Quantum Processor with an Error-Resilient Algorithm. United States. doi:10.1103/PhysRevX.8.011021.
Colless, J. I., Ramasesh, V. V., Dahlen, D., Blok, M. S., Kimchi-Schwartz, M. E., McClean, J. R., Carter, J., de Jong, W. A., and Siddiqi, I.. 2018. "Computation of Molecular Spectra on a Quantum Processor with an Error-Resilient Algorithm". United States. doi:10.1103/PhysRevX.8.011021.
@article{osti_1420209,
title = {Computation of Molecular Spectra on a Quantum Processor with an Error-Resilient Algorithm},
author = {Colless, J. I. and Ramasesh, V. V. and Dahlen, D. and Blok, M. S. and Kimchi-Schwartz, M. E. and McClean, J. R. and Carter, J. and de Jong, W. A. and Siddiqi, I.},
abstractNote = {Harnessing the full power of nascent quantum processors requires the efficient management of a limited number of quantum bits with finite coherent lifetimes. Hybrid algorithms, such as the variational quantum eigensolver (VQE), leverage classical resources to reduce the required number of quantum gates. Experimental demonstrations of VQE have resulted in calculation of Hamiltonian ground states, and a new theoretical approach based on a quantum subspace expansion (QSE) has outlined a procedure for determining excited states that are central to dynamical processes. Here, we use a superconducting-qubit-based processor to apply the QSE approach to the H2 molecule, extracting both ground and excited states without the need for auxiliary qubits or additional minimization. Further, we show that this extended protocol can mitigate the effects of incoherent errors, potentially enabling larger-scale quantum simulations without the need for complex error-correction techniques.},
doi = {10.1103/PhysRevX.8.011021},
journal = {Physical Review. X},
number = 1,
volume = 8,
place = {United States},
year = {2018},
month = {2}
}

Works referenced in this record:

Self—Consistent Molecular Orbital Methods. XII. Further Extensions of Gaussian—Type Basis Sets for Use in Molecular Orbital Studies of Organic Molecules
journal, March 1972
  • Hehre, W. J.; Ditchfield, R.; Pople, J. A.
  • The Journal of Chemical Physics, Vol. 56, Issue 5, p. 2257-2261
  • DOI: 10.1063/1.1677527