Two of the most active areas in quantum many-particle dynamics involve systems with an unusually large number of conservation laws. Many-body-localized systems generalize ideas of Anderson localization by disorder to interacting systems. While localization still exists with interactions and inhibits thermalization, the interactions between conserved quantities lead to some dramatic differences from the Anderson case. Quantum integrable models such as the XXZ spin chain or Bose gas with delta-function interactions also have infinite sets of conservation laws, again leading to modifications of conventional thermalization. A practical way to treat the hydrodynamic evolution from local equilibrium to global equilibrium in such models is discussed. This paper expands upon a presentation at a discussion meeting of the Royal Society on 7 February 2017. The work described was carried out with a number of collaborators, including Jens Bardarson, Vir Bulchandani, Roni Ilan, Christoph Karrasch, Siddharth Parameswaran, Frank Pollmann and Romain Vasseur.This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'.Two of the most active areas in quantum many-particle dynamics involve systems with an unusually large number of conservation laws. Many-body-localized systems generalize ideas of Anderson localization by disorder to interacting systems. While localization still exists with interactions and inhibits thermalization, the interactions between conserved quantities lead to some dramatic differences from the Anderson case. Quantum integrable models such as the XXZ spin chain or Bose gas with delta-function interactions also have infinite sets of conservation laws, again leading to modifications of conventional thermalization. A practical way to treat the hydrodynamic evolution from local equilibrium to global equilibrium in such models is discussed. This paper expands upon a presentation at a discussion meeting of the Royal Society on 7 February 2017. The work described was carried out with a number of collaborators, including Jens Bardarson, Vir Bulchandani, Roni Ilan, Christoph Karrasch, Siddharth Parameswaran, Frank Pollmann and Romain Vasseur.This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'.

Philosophical Transactions of the Royal Society A Mathematical Physical and Engineering SciencesOct 30, 20174 citations

SYNTHETIC QUANTUM MANY-BODY SYSTEMS

Christine Guerlin, Kristian Baumann, Ferdinand Brennecke +8 more

Laser SpectroscopyFeb 1, 20100 citations

Multipartite entanglement in a non-Hermitian quadruple-well potential with synthetic gauge fields

Yan-Qiong Ma, Ke-Wen Xiao, Cheng-Jie Wang +1 more

Multipartite entanglement lies at the heart of quantum many-body physics and quantum information science, serving as a key resource for quantum computation, quantum simulation, and quantum metrology. While its behavior in Hermitian systems has been extensively studied, its fate in non-Hermitian systems, especially those with synthetic gauge fields, remains largely unexplored. In this work we investigate multipartite entanglement dynamics in a quadruple-well system under the influence of synthetic gauge fields and nonreciprocal coupling. By constructing a many-body Hamiltonian that incorporates synthetic gauge fluxes, interaction-induced nonlinearity, and parity-time ( $\mathcal{PT}$ ) symmetry-breaking terms, we reveal that the interplay between non-Hermiticity and gauge fields provides unprecedented control over entanglement structures and their evolution. Notably, the synthetic gauge field acts as a tunable switch for entanglement configurations, enabling transitions between separable, bipartite, tripartite, and globally entangled configurations. Furthermore, we uncover a striking odd-even effect of particle number on both $\mathcal{PT}$ -symmetry phase transitions and entanglement patterns, highlighting the role of particle-number parity in non-Hermitian many-body systems. These findings not only deepen our understanding of many-body quantum correlations in non-Hermitian systems but also open alternative avenues for designing entanglement-resolved quantum sensors and preparing topologically nontrivial many-body states in synthetic quantum platforms.Multipartite entanglement lies at the heart of quantum many-body physics and quantum information science, serving as a key resource for quantum computation, quantum simulation, and quantum metrology. While its behavior in Hermitian systems has been extensively studied, its fate in non-Hermitian systems, especially those with synthetic gauge fields, remains largely unexplored. In this work we investigate multipartite entanglement dynamics in a quadruple-well system under the influence of synthetic gauge fields and nonreciprocal coupling. By constructing a many-body Hamiltonian that incorporates synthetic gauge fluxes, interaction-induced nonlinearity, and parity-time ($\mathcal{PT}$) symmetry-breaking terms, we reveal that the interplay between non-Hermiticity and gauge fields provides unprecedented control over entanglement structures and their evolution. Notably, the synthetic gauge field acts as a tunable switch for entanglement configurations, enabling transitions between separable, bipartite, tripartite, and globally entangled configurations. Furthermore, we uncover a striking odd-even effect of particle number on both $\mathcal{PT}$-symmetry phase transitions and entanglement patterns, highlighting the role of particle-number parity in non-Hermitian many-body systems. These findings not only deepen our understanding of many-body quantum correlations in non-Hermitian systems but also open alternative avenues for designing entanglement-resolved quantum sensors and preparing topologically nontrivial many-body states in synthetic quantum platforms.

Physical Review ADec 1, 20250 citations

QUANTUM MANY-BODY SYSTEMS WITH SHORT-RANGE INTERACTIONS

Jun O. S. Yin

Jan 1, 20082 citations

Creating locally interacting Hamiltonians in the synthetic frequency dimension for photons

Luqi Yuan, Avik Dutt, Mingpu Qin +2 more

The recent emerging field of synthetic dimension in photonics offers a variety of opportunities for manipulating different internal degrees of freedom of photons such as the spectrum of light. While nonlinear optical effects can be incorporated into these photonic systems with synthetic dimensions, these nonlinear effects typically result in long-range interactions along the frequency axis. Thus, it has been difficult to use the synthetic dimension concept to study a large class of Hamiltonians that involves local interactions. Here we show that a Hamiltonian that is locally interacting along the synthetic dimension can be achieved in a dynamically modulated ring resonator incorporating χ ( 3 ) nonlinearity, provided that the group velocity dispersion of the waveguide forming the ring is specifically designed. As a demonstration we numerically implement a Bose–Hubbard model and explore photon blockade effect in the synthetic frequency space. Our work opens new possibilities for studying fundamental many-body physics in the synthetic space in photonics, with potential applications in optical quantum communication and quantum computation.The recent emerging field of synthetic dimension in photonics offers a variety of opportunities for manipulating different internal degrees of freedom of photons such as the spectrum of light. While nonlinear optical effects can be incorporated into these photonic systems with synthetic dimensions, these nonlinear effects typically result in long-range interactions along the frequency axis. Thus, it has been difficult to use the synthetic dimension concept to study a large class of Hamiltonians that involves local interactions. Here we show that a Hamiltonian that is locally interacting along the synthetic dimension can be achieved in a dynamically modulated ring resonator incorporating χ ( 3 ) nonlinearity, provided that the group velocity dispersion of the waveguide forming the ring is specifically designed. As a demonstration we numerically implement a Bose–Hubbard model and explore photon blockade effect in the synthetic frequency space. Our work opens new possibilities for studying fundamental many-body physics in the synthetic space in photonics, with potential applications in optical quantum communication and quantum computation.

arXiv:1909.12466Photonics ResearchJul 13, 202033 citations

Quantum Many-Body Systems

Chon‐Fai Kam, Wei-Min Zhang, D.H. Feng

Lecture notes in physicsNov 2, 202210 citations

\mathcal{PT}

) symmetry-breaking terms, we reveal that the interplay between non-Hermiticity and gauge fields provides unprecedented control over entanglement structures and their evolution. Notably, the synthetic gauge field acts as a tunable switch for entanglement configurations, enabling transitions between separable, bipartite, tripartite, and globally entangled configurations. Furthermore, we uncover a striking odd-even effect of particle number on both

\mathcal{PT}

-symmetry phase transitions and entanglement patterns, highlighting the role of particle-number parity in non-Hermitian many-body systems. These findings not only deepen our understanding of many-body quantum correlations in non-Hermitian systems but also open alternative avenues for designing entanglement-resolved quantum sensors and preparing topologically nontrivial many-body states in synthetic quantum platforms.