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Generation of thermofield double states and critical ground states with a quantum computer

TitleGeneration of thermofield double states and critical ground states with a quantum computer
Publication TypeJournal Article
Year of Publication2020
AuthorsD.. Zhu, S.. Johri, N.. M. Linke, K.. A. Landsman, H. C. Alderete, N.. H. Nguyen, A.. Y. Matsuura, T.. H. Hsieh, and C.. Monroe
JournalProc. Natl. Acad. Sci. U. S. A.
Volume117
Pagination25402–25406
Date Publishedoct
ISSN0027-8424
KeywordsIsing model, quantum computing, quantum simulation, thermofield double state, trapped ions
Abstract

Finite-temperature phases of many-body quantum systems are fundamental to phenomena ranging from condensed-matter physics to cosmology, yet they are generally difficult to simulate. Using an ion trap quantum computer and protocols motivated by the quantum approximate optimization algorithm (QAOA), we generate nontrivial thermal quantum states of the transversefield Ising model (TFIM) by preparing thermofield double states at a variety of temperatures. We also prepare the critical state of the TFIM at zero temperature using quantum?classical hybrid optimization. The entanglement structure of thermofield double and critical states plays a key role in the study of black holes, and our work simulates such nontrivial structures on a quantum computer. Moreover, we find that the variational quantum circuits exhibit noise thresholds above which the lowest-depth QAOA circuits provide the best results.

DOI10.1073/pnas.2006337117