Entanglement asymmetry as a probe of symmetry breaking

Symmetry and symmetry breaking are two pillars of modern quantum physics. Still, quantifying how much a symmetry is broken is an issue that has received little attention. In extended quantum systems, this problem is intrinsically bound to the subsystem of interest. Hence, in this work, we borrow met...

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Bibliographic Details
Published in:Nature communications 2023-04, Vol.14 (1), p.2036-7, Article 2036
Main Authors: Ares, Filiberto, Murciano, Sara, Calabrese, Pasquale
Format: Article
Language:English
Subjects:
639/766/483/1139
639/766/483/640
Asymmetry
Broken symmetry
Chains
Elementary excitations
Humanities and Social Sciences
multidisciplinary
Quantum entanglement
Quantum theory
Science
Science (multidisciplinary)
Spin dynamics
Subsystems
Symmetry
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Summary:Symmetry and symmetry breaking are two pillars of modern quantum physics. Still, quantifying how much a symmetry is broken is an issue that has received little attention. In extended quantum systems, this problem is intrinsically bound to the subsystem of interest. Hence, in this work, we borrow methods from the theory of entanglement in many-body quantum systems to introduce a subsystem measure of symmetry breaking that we dub entanglement asymmetry . As a prototypical illustration, we study the entanglement asymmetry in a quantum quench of a spin chain in which an initially broken global U (1) symmetry is restored dynamically. We adapt the quasiparticle picture for entanglement evolution to the analytic determination of the entanglement asymmetry. We find, expectedly, that larger is the subsystem, slower is the restoration, but also the counterintuitive result that more the symmetry is initially broken, faster it is restored, a sort of quantum Mpemba effect, a phenomenon that we show to occur in a large variety of systems. A measure of symmetry breaking in a quantum many-body system could provide insight into its dynamics. Ares et al. introduce a subsystem measure of symmetry breaking dubbed entanglement asymmetry and apply it to quantum quench dynamics in spin chains, revealing a quantum analogue of the Mpemba effect.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-023-37747-8