Symmetry restoration and quantum Mpemba effect in symmetric random circuits

Symmetry restoration and quantum Mpemba effect in symmetric random circuits

November 11, 2024 | Shuo Liu, Hao-Kai Zhang, Shuai Yin, Shi-Xin Zhang
This study investigates symmetry restoration and the quantum Mpemba effect in symmetric random quantum circuits. The research focuses on the U(1) symmetry case, revealing that symmetry restoration can fail in U(1)-symmetric circuits for certain weak symmetry-broken initial states in finite systems. In contrast, non-symmetric circuits always restore U(1) symmetry at late times. The quantum Mpemba effect is observed, where symmetry is restored faster for more asymmetric initial states. The study also examines SU(2) and Z₂ symmetric circuits, identifying the presence or absence of the quantum Mpemba effect for these symmetries. A unified understanding is provided through the lens of quantum thermalization with conserved charges. The research explores the dynamics of subsystem symmetry restoration across various symmetric and non-symmetric quantum random circuits. Entanglement asymmetry (EA) is used to quantify symmetry breaking and restoration. The EA dynamics show that the quantum Mpemba effect emerges in U(1)-symmetric circuits, where symmetry is restored more quickly for more asymmetric initial states. This effect is absent in non-symmetric circuits. The study also investigates the role of conserved charges and their impact on thermalization, showing that charge sectors with small Hilbert space dimensions do not thermalize or do so slowly, leading to slower symmetry restoration. The findings highlight the differences between U(1)-symmetric and non-symmetric circuits in terms of symmetry restoration and quantum thermalization. The quantum Mpemba effect is observed in early-time dynamics, where more asymmetric initial states lead to faster symmetry restoration. The study also extends the definition of EA to SU(2) cases, showing that the quantum Mpemba effect can occur in these systems as well. The results provide insights into the mechanisms underlying the quantum Mpemba effect in generic chaotic systems, emphasizing the role of thermalization and conserved charges in symmetry restoration. The study concludes that the quantum Mpemba effect is a significant phenomenon in quantum systems, with implications for understanding quantum thermalization and symmetry restoration in various contexts.This study investigates symmetry restoration and the quantum Mpemba effect in symmetric random quantum circuits. The research focuses on the U(1) symmetry case, revealing that symmetry restoration can fail in U(1)-symmetric circuits for certain weak symmetry-broken initial states in finite systems. In contrast, non-symmetric circuits always restore U(1) symmetry at late times. The quantum Mpemba effect is observed, where symmetry is restored faster for more asymmetric initial states. The study also examines SU(2) and Z₂ symmetric circuits, identifying the presence or absence of the quantum Mpemba effect for these symmetries. A unified understanding is provided through the lens of quantum thermalization with conserved charges. The research explores the dynamics of subsystem symmetry restoration across various symmetric and non-symmetric quantum random circuits. Entanglement asymmetry (EA) is used to quantify symmetry breaking and restoration. The EA dynamics show that the quantum Mpemba effect emerges in U(1)-symmetric circuits, where symmetry is restored more quickly for more asymmetric initial states. This effect is absent in non-symmetric circuits. The study also investigates the role of conserved charges and their impact on thermalization, showing that charge sectors with small Hilbert space dimensions do not thermalize or do so slowly, leading to slower symmetry restoration. The findings highlight the differences between U(1)-symmetric and non-symmetric circuits in terms of symmetry restoration and quantum thermalization. The quantum Mpemba effect is observed in early-time dynamics, where more asymmetric initial states lead to faster symmetry restoration. The study also extends the definition of EA to SU(2) cases, showing that the quantum Mpemba effect can occur in these systems as well. The results provide insights into the mechanisms underlying the quantum Mpemba effect in generic chaotic systems, emphasizing the role of thermalization and conserved charges in symmetry restoration. The study concludes that the quantum Mpemba effect is a significant phenomenon in quantum systems, with implications for understanding quantum thermalization and symmetry restoration in various contexts.
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Understanding Symmetry Restoration and Quantum Mpemba Effect in Symmetric Random Circuits.