Gate-free state preparation for fast variational quantum eigensolver simulations

The variational quantum eigensolver is currently the flagship algorithm for solving electronic structure problems on near-term quantum computers. The algorithm involves implementing a sequence of parameterized gates on quantum hardware to generate a target quantum state, and then measuring the molec...

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Bibliographic Details
Published in:npj quantum information 2021-10, Vol.7 (1), p.1-11, Article 155
Main Authors: Meitei, Oinam Romesh, Gard, Bryan T., Barron, George S., Pappas, David P., Economou, Sophia E., Barnes, Edwin, Mayhall, Nicholas J.
Format: Article
Language:English
Subjects:
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639/766/483/481
Algorithms
Classical and Quantum Gravitation
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
computation
Computers
information theory
Physics
Physics and Astronomy
quantum chemistry
Quantum Computing
Quantum Field Theories
quantum information
Quantum Information Technology
Quantum Physics
Relativity Theory
Spintronics
String Theory
theoretical chemistry
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Summary:The variational quantum eigensolver is currently the flagship algorithm for solving electronic structure problems on near-term quantum computers. The algorithm involves implementing a sequence of parameterized gates on quantum hardware to generate a target quantum state, and then measuring the molecular energy. Due to finite coherence times and gate errors, the number of gates that can be implemented remains limited. In this work, we propose an alternative algorithm where device-level pulse shapes are variationally optimized for the state preparation rather than using an abstract-level quantum circuit. In doing so, the coherence time required for the state preparation is drastically reduced. We numerically demonstrate this by directly optimizing pulse shapes which accurately model the dissociation of H 2 and HeH + , and we compute the ground state energy for LiH with four transmons where we see reductions in state preparation times of roughly three orders of magnitude compared to gate-based strategies.
ISSN:2056-6387
2056-6387
DOI:10.1038/s41534-021-00493-0