Exact Many-body Quantum Dynamics in One-Dimensional Baths via "Superspins"

Fuente: arXiv
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Auteurs principaux: Lee, Joseph T., Cardenas-Lopez, Silvia, Masson, Stuart J., Trivedi, Rahul, Asenjo-Garcia, Ana
Format: Preprint
Publié: 2025
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author Lee, Joseph T.
Cardenas-Lopez, Silvia
Masson, Stuart J.
Trivedi, Rahul
Asenjo-Garcia, Ana
author_facet Lee, Joseph T.
Cardenas-Lopez, Silvia
Masson, Stuart J.
Trivedi, Rahul
Asenjo-Garcia, Ana
contents Computing the exact dynamics of many-body quantum systems becomes intractable as system size grows. Here, we present a symmetry-based method that provides an exponential reduction in the complexity of a broad class of such problems $\unicode{x2014}$ qubits coupled to one-dimensional electromagnetic baths. We identify conditions under which partial permutational symmetry emerges and exploit it to group qubits into collective multi-level degrees of freedom, which we term ''superspins.'' These superspins obey a generalized angular momentum algebra, reducing the relevant Hilbert space dimension from exponential to polynomial. Using this framework, we efficiently compute many-body superradiant dynamics in large arrays of qubits coupled to waveguides and ring resonators, showing that $\unicode{x2014}$ unlike in conventional Dicke superradiance $\unicode{x2014}$ the total spin length is not conserved. At long times, dark states become populated. We identify configurations where these states exhibit metrologically useful entanglement. Our approach enables exact treatment of complex dissipative dynamics beyond the fully symmetric limit and provides a rigorous benchmark for approximate numerical methods.
format Preprint
id arxiv_https___arxiv_org_abs_2505_00588
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Exact Many-body Quantum Dynamics in One-Dimensional Baths via "Superspins"
Lee, Joseph T.
Cardenas-Lopez, Silvia
Masson, Stuart J.
Trivedi, Rahul
Asenjo-Garcia, Ana
Quantum Physics
Computing the exact dynamics of many-body quantum systems becomes intractable as system size grows. Here, we present a symmetry-based method that provides an exponential reduction in the complexity of a broad class of such problems $\unicode{x2014}$ qubits coupled to one-dimensional electromagnetic baths. We identify conditions under which partial permutational symmetry emerges and exploit it to group qubits into collective multi-level degrees of freedom, which we term ''superspins.'' These superspins obey a generalized angular momentum algebra, reducing the relevant Hilbert space dimension from exponential to polynomial. Using this framework, we efficiently compute many-body superradiant dynamics in large arrays of qubits coupled to waveguides and ring resonators, showing that $\unicode{x2014}$ unlike in conventional Dicke superradiance $\unicode{x2014}$ the total spin length is not conserved. At long times, dark states become populated. We identify configurations where these states exhibit metrologically useful entanglement. Our approach enables exact treatment of complex dissipative dynamics beyond the fully symmetric limit and provides a rigorous benchmark for approximate numerical methods.
title Exact Many-body Quantum Dynamics in One-Dimensional Baths via "Superspins"
topic Quantum Physics
url https://arxiv.org/abs/2505.00588