Nonunitary Operations for Ground-State Calculations in Near-Term Quantum Computers

Guglielmo Mazzola, Pauline J. Ollitrault, Panagiotis Kl. Barkoutsos, and Ivano Tavernelli
Phys. Rev. Lett. 123, 130501 – Published 27 September 2019
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Abstract

We introduce a quantum Monte Carlo inspired reweighting scheme to accurately compute energies from optimally short quantum circuits. This effectively hybrid quantum-classical approach features both entanglement provided by a short quantum circuit, and the presence of an effective nonunitary operator at the same time. The functional form of this projector is borrowed from classical computation and is able to filter out high-energy components generated by a suboptimal variational quantum heuristic Ansatz. The accuracy of this approach is demonstrated numerically in finding energies of entangled ground states of many-body lattice models. We demonstrate a practical implementation on IBM quantum hardware up to an 8-qubit circuit.

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  • Received 9 July 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.130501

© 2019 American Physical Society

Physics Subject Headings (PhySH)

Quantum Information, Science & Technology

Authors & Affiliations

Guglielmo Mazzola1,*, Pauline J. Ollitrault1,2, Panagiotis Kl. Barkoutsos1, and Ivano Tavernelli1

  • 1IBM Research Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
  • 2Laboratory of Physical Chemistry, ETH Zürich, 8093 Zürich, Switzerland

  • *GMA@zurich.ibm.com

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Issue

Vol. 123, Iss. 13 — 27 September 2019

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