Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical review. B./Physical review. B

Long-term evolution of non-Hermitian systems in quantum-walk dynamics

Xiang‐Long Yu, Pei-Ling Huang, Pei-Hao Fu, Jiansheng Wu

Published Mar 28, 2024• 0 citations
Publisher

Abstract

We present a study on the long-term evolution of a non-Hermitian one-dimensional system with on-site dissipations in quantum-walk dynamics. By investigating various cases, including different evolution operations, lattice sizes, initial positions, and dissipations, we uncover remarkable and unconventional features. They include the emergence of distinct final states after a sufficiently long evolution time, the persistence of metastable states for extended periods, the survival of extended states only within the inner region of a domain-wall structure, and the occurrence of instantaneous ultrafar jumps during the evolution process. To provide insight into the underlying physical mechanisms behind these observations, we undertake a comprehensive investigation accompanied by detailed analysis, clarify the relation between time-evolved (meta)stable states and system eigenstates, and analyze the symmetry of final states. Moreover, our research reveals some phenomena that differ from those seen in previous experimental results, which can be attributed to the limited evolution time in the experiments. These theoretical findings underscore the significance of long-term evolution in non-Hermitian systems based on quantum walks.

DOI
10.1103/physrevb.109.115158

Related papers

Non-Hermitian Dynamics in Three-Level Systems: A Perturbative Approach for Time-Dependent Hamiltonians

Gui-Xiang La, Yexin Li, Gong-Ping Zheng

The conventional time-dependent perturbation theory in quantum mechanics is established within the framework of Hermitian Hamiltonians, applicable for describing quantum transitions and associated energy level responses in such systems. However, this theory has fundamental limitations when applied to non-Hermitian systems. Consequently, researchers have systematically extended time-dependent perturbation theory to non-Hermitian systems, establishing a corresponding mature framework. Building on this foundation, this study extends the theory to investigate the transition dynamics induced by non-Hermitian interactions in non-Hermitian Hamiltonian systems. We employ a biorthogonal basis representation for a three-level non-Hermitian system. This work investigates a system comprising an unperturbed static non-Hermitian Hamiltonian and a periodically driven time-dependent perturbation Hamiltonian. Taking the three-level system as a concrete example, we combine analytical methods with numerical simulations to solve and analyze its dynamical evolution equations. These complementary approaches reveal that when system parameters complete a full cycle around an exceptional point, the transitional behavior exhibits specific evolutionary patterns. In this system, quantum transition probabilities exhibit significant asymmetry and non-conservation that depend on the initial and final states, revealing inherent directional characteristics in the dynamical process. Furthermore, for a three-level, periodically driven non-Hermitian system with time-dependent perturbations, this asymmetry is even more pronounced, manifesting as a distinct disparity between forward and reverse transition probabilities. The periodic driving actively amplifies the asymmetry in the transition process. By designing the perturbation spectrum, selective manipulation of specific quantum states can be achieved. Moreover, transition probabilities can be significantly enhanced under resonance conditions, while non-Hermiticity further breaks the system's inherent symmetry, leading to substantial amplification of transitions in a single direction. By precisely tuning the drive frequency, interactions between specific coupling channels can be selectively enhanced or suppressed. The amplification of channel asymmetry by non-Hermitian properties provides a novel mechanism for directional control of quantum states and opens new pathways for realizing related quantum technologies.

Entropy•Feb 28, 2026•0 citations

One-dimensional quantum walk with a moving boundary

L. C. Kwek, Setiawan

Quantum walks are interesting models with potential applications to quantum algorithms and physical processes such as photosynthesis. In this paper, we study two models of one-dimensional quantum walks, namely, quantum walks with a moving absorbing wall and quantum walks with one stationary and one moving absorbing wall. For the former, we calculate numerically the survival probability, the rate of change of average position, and the rate of change of standard deviation of the particle's position in the long time limit for different wall velocities. Moreover, we also study the asymptotic behavior and the dependence of the survival probability on the initial particle's state. While for the latter, we compute the absorption probability of the right stationary wall for different velocities and initial positions of the left wall boundary. The results for these two models are compared with those obtained for the classical model. The difference between the results obtained for the quantum and classical models can be attributed to the difference in the probability distributions.

Physical Review A•Sep 15, 2011•14 citations

Non-Hermiticity-induced quantum control of localization in quantum walks

Rui Zhang, Yi-Fan Liu, Tian Chen

Non-Hermiticity-induced quantum control is an unique phenomenon, which cannot be observed in Hermitian quantum systems. Here we study the quantum control of localization in non-Hermitian QW systems. When a phase defect is introduced to a specific site of non-Hermitian QW, the walker will not only be localized at the site of phase defect but also at its neighboring sites. Moreover, we find that as the system transforms from the $\mathcal{PT}$-symmetry-unbroken regime to $\mathcal{PT}$-symmetry-broken regime, most of probability distributions can be found at the positions far away from the phase defect in a long period of time. Our discoveries about the control of walker in non-Hermitian QW can provide valuable references for the study of quantum search in dissipative quantum systems.

Physical Review A•Aug 19, 2020•10 citations

Self-normal and biorthogonal dynamical quantum phase transitions in non-Hermitian quantum walks

Haiting Zhang, Kunkun Wang, Lei Xiao +1 more

Dynamical quantum phase transitions (DQPTs), characterized by non-analytic behavior in rate function and abrupt changes in dynamic topological order parameters (DTOPs) over time, have garnered enormous attention in recent decades. However, in non-Hermitian systems, the special biorthogonality of the bases makes the definition of DQPTs complex. In this work, we delve into the comprehensive investigation of self-normal DQPTs (originally used in Hermitian systems) to compare them with their biorthogonal counterpart, within the context of non-Hermitian quantum walks (QWs). We present a detailed analysis of the behaviors of Loschmidt rate functions and DTOPs under these two distinct theoretical approaches. While both self-normal and biorthogonal methods can be used to detect DQPTs in quench dynamics between different topological phases, we theoretically present their differences in the definition of critical momenta and critical times by analyzing the Fisher zeros and fixed points. Finally, we present an experiment that observes both types of DQPTs using one-dimensional discrete-time QWs with single photons.

Light Science & Applications•Jul 26, 2025•12 citations

Non-Hermitian quantum walks uncover dynamical quantum phase transitions under self-normal and biorthogonal bases

Guangzhen Li, Luqi Yuan

The differences in critical times and critical momenta between self-normal and biorthogonal dynamical quantum phase transitions are revealed. The theoretical analysis is experimentally validated through multiple quench processes using a one-dimensional discrete-time non-Hermitian quantum walks.

Light Science & Applications•Jan 4, 2026•2 citations

Investigation of a non-Hermitian edge burst with time-dependent perturbation theory

Pengyu Wen, Jinghui Pi, Gui‐Lu Long

Edge burst is a phenomenon in non-Hermitian quantum dynamics discovered by a recent numerical study [Phys. Rev. Lett. 128, 120401 (2022)]. It finds that a large proportion of particle loss occurs at the system boundary in a class of non-Hermitian quantum walk. In this paper, we investigate the evolution of real-space wave functions for this lattice system. We find the wave function of the edge site is distinct from the bulk sites. Using time-dependent perturbation theory, we derive the analytical expression of the real-space wave functions and find that the different evolution behaviors between the edge and bulk sites are due to their different nearest-neighbor site configurations. We also find the edge wave function primarily results from the transition of the two nearest-neighbor nondecay sites. Besides, the numerical diagonalization shows the edge wave function is mainly propagated by a group of eigenmodes with a relatively large imaginary part. Our work provides an analytical method for studying non-Hermitian quantum dynamical problems.

arXiv:2303.17219•Physical Review A•Feb 26, 2024•11 citations
We present a study on the long-term evolution of a non-Hermitian one-dimensional system with on-site dissipations in quantum-walk dynamics. By investigating various cases, including different evolution operations, lattice sizes, initial positions, and dissipations, we uncover remarkable and unconventional features. They include the emergence of distinct final states after a sufficiently long evolution time, the persistence of metastable states for extended periods, the survival of extended states only within the inner region of a domain-wall structure, and the occurrence of instantaneous ultrafar jumps during the evolution process. To provide insight into the underlying physical mechanisms behind these observations, we undertake a comprehensive investigation accompanied by detailed analysis, clarify the relation between time-evolved (meta)stable states and system eigenstates, and analyze the symmetry of final states. Moreover, our research reveals some phenomena that differ from those seen in previous experimental results, which can be attributed to the limited evolution time in the experiments. These theoretical findings underscore the significance of long-term evolution in non-Hermitian systems based on quantum walks.
The conventional time-dependent perturbation theory in quantum mechanics is established within the framework of Hermitian Hamiltonians, applicable for describing quantum transitions and associated energy level responses in such systems. However, this theory has fundamental limitations when applied to non-Hermitian systems. Consequently, researchers have systematically extended time-dependent perturbation theory to non-Hermitian systems, establishing a corresponding mature framework. Building on this foundation, this study extends the theory to investigate the transition dynamics induced by non-Hermitian interactions in non-Hermitian Hamiltonian systems. We employ a biorthogonal basis representation for a three-level non-Hermitian system. This work investigates a system comprising an unperturbed static non-Hermitian Hamiltonian and a periodically driven time-dependent perturbation Hamiltonian. Taking the three-level system as a concrete example, we combine analytical methods with numerical simulations to solve and analyze its dynamical evolution equations. These complementary approaches reveal that when system parameters complete a full cycle around an exceptional point, the transitional behavior exhibits specific evolutionary patterns. In this system, quantum transition probabilities exhibit significant asymmetry and non-conservation that depend on the initial and final states, revealing inherent directional characteristics in the dynamical process. Furthermore, for a three-level, periodically driven non-Hermitian system with time-dependent perturbations, this asymmetry is even more pronounced, manifesting as a distinct disparity between forward and reverse transition probabilities. The periodic driving actively amplifies the asymmetry in the transition process. By designing the perturbation spectrum, selective manipulation of specific quantum states can be achieved. Moreover, transition probabilities can be significantly enhanced under resonance conditions, while non-Hermiticity further breaks the system's inherent symmetry, leading to substantial amplification of transitions in a single direction. By precisely tuning the drive frequency, interactions between specific coupling channels can be selectively enhanced or suppressed. The amplification of channel asymmetry by non-Hermitian properties provides a novel mechanism for directional control of quantum states and opens new pathways for realizing related quantum technologies.
Quantum walks are interesting models with potential applications to quantum algorithms and physical processes such as photosynthesis. In this paper, we study two models of one-dimensional quantum walks, namely, quantum walks with a moving absorbing wall and quantum walks with one stationary and one moving absorbing wall. For the former, we calculate numerically the survival probability, the rate of change of average position, and the rate of change of standard deviation of the particle's position in the long time limit for different wall velocities. Moreover, we also study the asymptotic behavior and the dependence of the survival probability on the initial particle's state. While for the latter, we compute the absorption probability of the right stationary wall for different velocities and initial positions of the left wall boundary. The results for these two models are compared with those obtained for the classical model. The difference between the results obtained for the quantum and classical models can be attributed to the difference in the probability distributions.
Non-Hermiticity-induced quantum control is an unique phenomenon, which cannot be observed in Hermitian quantum systems. Here we study the quantum control of localization in non-Hermitian QW systems. When a phase defect is introduced to a specific site of non-Hermitian QW, the walker will not only be localized at the site of phase defect but also at its neighboring sites. Moreover, we find that as the system transforms from the PT\mathcal{PT}PT-symmetry-unbroken regime to PT\mathcal{PT}PT-symmetry-broken regime, most of probability distributions can be found at the positions far away from the phase defect in a long period of time. Our discoveries about the control of walker in non-Hermitian QW can provide valuable references for the study of quantum search in dissipative quantum systems.
Dynamical quantum phase transitions (DQPTs), characterized by non-analytic behavior in rate function and abrupt changes in dynamic topological order parameters (DTOPs) over time, have garnered enormous attention in recent decades. However, in non-Hermitian systems, the special biorthogonality of the bases makes the definition of DQPTs complex. In this work, we delve into the comprehensive investigation of self-normal DQPTs (originally used in Hermitian systems) to compare them with their biorthogonal counterpart, within the context of non-Hermitian quantum walks (QWs). We present a detailed analysis of the behaviors of Loschmidt rate functions and DTOPs under these two distinct theoretical approaches. While both self-normal and biorthogonal methods can be used to detect DQPTs in quench dynamics between different topological phases, we theoretically present their differences in the definition of critical momenta and critical times by analyzing the Fisher zeros and fixed points. Finally, we present an experiment that observes both types of DQPTs using one-dimensional discrete-time QWs with single photons.
Edge burst is a phenomenon in non-Hermitian quantum dynamics discovered by a recent numerical study [Phys. Rev. Lett. 128, 120401 (2022)]. It finds that a large proportion of particle loss occurs at the system boundary in a class of non-Hermitian quantum walk. In this paper, we investigate the evolution of real-space wave functions for this lattice system. We find the wave function of the edge site is distinct from the bulk sites. Using time-dependent perturbation theory, we derive the analytical expression of the real-space wave functions and find that the different evolution behaviors between the edge and bulk sites are due to their different nearest-neighbor site configurations. We also find the edge wave function primarily results from the transition of the two nearest-neighbor nondecay sites. Besides, the numerical diagonalization shows the edge wave function is mainly propagated by a group of eigenmodes with a relatively large imaginary part. Our work provides an analytical method for studying non-Hermitian quantum dynamical problems.