Please use this identifier to cite or link to this item: http://hdl.handle.net/10497/24065
Title: 
Authors: 
Issue Date: 
2022
Citation: 
Lau, J. W., Haug, T., Kwek, L. C., & Kishor Bharti. (2022). NISQ algorithm for Hamiltonian simulation via truncated Taylor series. SciPost Physics, 12(4), Article 122. https://doi.org/10.21468/scipostphys.12.4.122
Journal: 
SciPost Physics
Abstract: 
Simulating the dynamics of many-body quantum systems is believed to be one of the first fields that quantum computers can show a quantum advantage over classical computers. Noisy intermediate-scale quantum (NISQ) algorithms aim at effectively using the currently available quantum hardware. For quantum simulation, various types of NISQ algorithms have been proposed with individual advantages as well as challenges. In this work, we propose a new algorithm, truncated Taylor quantum simulator (TQS), that shares the advantages of existing algorithms and alleviates some of the shortcomings. Our algorithm does not have any classical-quantum feedback loop and bypasses the barren plateau problem by construction. The classical part in our hybrid quantum-classical algorithm corresponds to a quadratically constrained quadratic program (QCQP) with a single quadratic equality constraint, which admits a semidefinite relaxation. The QCQP based classical optimization was recently introduced as the classical step in quantum assisted eigensolver (QAE), a NISQ algorithm for the Hamiltonian ground state problem. Thus, our work provides a conceptual unification between the NISQ algorithms for the Hamiltonian ground state problem and the Hamiltonian simulation. We recover differential equation-based NISQ algorithms for Hamiltonian simulation such as quantum assisted simulator (QAS) and variational quantum simulator (VQS) as particular cases of our algorithm. We test our algorithm on some toy examples on current cloud quantum computers. We also provide a systematic approach to improve the accuracy of our algorithm.
Description: 
The open access publication is available at: https://doi.org/10.21468/scipostphys.12.4.122
URI: 
ISSN: 
2542-4653
DOI: 
Grant ID: 
EP/T001062/1
Funding Agency: 
National Research Foundation, Singapore
Ministry of Education, Singapore
Engineering and Physical Sciences Research Council [EPSRC]
International Business Machines Corporation (IBM)
File Permission: 
None
File Availability: 
No file
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