A Relation between Krylov and Nielsen Complexity

Krylov complexity and Nielsen complexity are successful approaches to quantifying quantum evolution complexity that have been actively pursued without much contact between the two lines of research. The two quantities are motivated by quantum chaos and quantum computation, respectively, while the re...

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Bibliographic Details
Published in:Physical review letters 2024-04, Vol.132 (16), p.160402-160402, Article 160402
Main Authors: Craps, Ben, Evnin, Oleg, Pascuzzi, Gabriele
Format: Article
Language:English
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Summary:Krylov complexity and Nielsen complexity are successful approaches to quantifying quantum evolution complexity that have been actively pursued without much contact between the two lines of research. The two quantities are motivated by quantum chaos and quantum computation, respectively, while the relevant mathematics is as different as matrix diagonalization algorithms and geodesic flows on curved manifolds. We demonstrate that, despite these differences, there is a relation between the two quantities. Namely, the time average of Krylov complexity of state evolution can be expressed as a trace of a certain matrix, which also controls an upper bound on Nielsen complexity with a specific custom-tailored penalty schedule adapted to the Krylov basis.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.132.160402