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arXiv · 2305.13356

Critical phase and spin sharpening in SU(2)-symmetric monitored quantum circuits

Shayan Majidy·Utkarsh Agrawal·Sarang Gopalakrishnan·Andrew C. Potter·Romain Vasseur·Nicole Yunger Halpern
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Abstract

Monitored quantum circuits exhibit entanglement transitions at certain measurement rates. Such a transition separates phases characterized by how much information an observer can learn from the measurement outcomes. We study SU(2)-symmetric monitored quantum circuits, using exact numerics and a mapping onto an effective statistical-mechanics model. Due to the symmetry's non-Abelian nature, measuring qubit pairs allows for nontrivial entanglement scaling even in the measurement-only limit. We find a transition between a volume-law entangled phase and a critical phase whose diffusive purification dynamics emerge from the non-Abelian symmetry. Additionally, we numerically identify a "spin-sharpening transition." On one side is a phase in which the measurements can efficiently identify the system's total spin quantum number; on the other side is a phase in which measurements cannot.

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Shayan Majidy, Utkarsh Agrawal, Sarang Gopalakrishnan, Andrew C. Potter, Romain Vasseur, Nicole Yunger Halpern. 2023-05-22. Critical phase and spin sharpening in SU(2)-symmetric monitored quantum circuits. https://doi.org/10.1103/physrevb.108.054307

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