Detecting Quantum Anomalies in Open Systems

• URL: http://arxiv.org/abs/2312.11188v2
• Date: Wed, 15 May 2024 02:54:59 GMT
• Title: Detecting Quantum Anomalies in Open Systems
• Authors: Yunlong Zang, Yingfei Gu, Shenghan Jiang,
• Abstract summary: We introduce a novel and experimentally feasible approach to detect quantum anomalies in open systems. We numerically demonstrate the unavoidable singular behavior of $exp(rmitheta Sz_rm tot)$ for half-integer spin chains.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Symmetries and quantum anomalies serve as powerful tools for constraining complicated quantum many-body systems, offering valuable insights into low-energy characteristics based on their ultraviolet structure. Nevertheless, their applicability has traditionally been confined to closed quantum systems, rendering them largely unexplored for open quantum systems described by density matrices. In this work, we introduce a novel and experimentally feasible approach to detect quantum anomalies in open systems. Specifically, we claim that, when coupled with an external environment, the mixed 't Hooft anomaly between spin rotation symmetry and lattice translation symmetry gives distinctive characteristics for half-integer and integer spin chains in measurements of $\exp(\rm{i}\theta S^z_{\rm tot})$ as a function of $\theta$. Notably, the half-integer spin chain manifests a topological phenomenon akin to the ``level crossing" observed in closed systems. To substantiate our assertion, we develop a lattice-level spacetime rotation to analyze the aforementioned measurements. Based on the matrix product density operator and transfer matrix formalism, we analytically establish and numerically demonstrate the unavoidable singular behavior of $\exp(\rm{i}\theta S^z_{\rm tot})$ for half-integer spin chains. Conceptually, our work demonstrates a way to discuss notions like ``spectral flow'' and ``flux threading'' in open systems not necessarily with a Hamiltonian.

Related papers

• Fourier Neural Operators for Learning Dynamics in Quantum Spin Systems [77.88054335119074]
  We use FNOs to model the evolution of random quantum spin systems. We apply FNOs to a compact set of Hamiltonian observables instead of the entire $2n$ quantum wavefunction.
  arXiv  Detail & Related papers  (2024-09-05T07:18:09Z)
• Symmetry: a fundamental resource for quantum coherence and metrology [0.0]
  We show that when the quantum state is an eigenstate of an operator $A$, observables $G$ which are completely off-diagonal have purely quantum fluctuations. This property holds regardless of the purity of the quantum state, and it implies that off-diagonal fluctuations represent a metrological resource for phase estimation.
  arXiv  Detail & Related papers  (2024-07-01T07:19:37Z)
• Measuring Spectral Form Factor in Many-Body Chaotic and Localized Phases of Quantum Processors [22.983795509221974]
  We experimentally measure the spectral form factor (SFF) to probe the presence or absence of chaos in quantum many-body systems. This work unveils a new way of extracting the universal signatures of many-body quantum chaos in quantum devices by probing the correlations in eigenenergies and eigenstates.
  arXiv  Detail & Related papers  (2024-03-25T16:59:00Z)
• Anomaly in open quantum systems and its implications on mixed-state quantum phases [6.356631694532754]
  We develop a systematic approach to characterize the 't Hooft anomaly in open quantum systems. By representing their symmetry transformation through superoperators, we incorporate them in a unified framework. We find that anomalies of bosonic systems are classified by $Hd+2(Ktimes G,U(1))/Hd+2(G,U(1))$ in $d$ spatial dimensions.
  arXiv  Detail & Related papers  (2024-03-21T16:34:37Z)
• Unified Framework for Open Quantum Dynamics with Memory [1.639482556214273]
  We show the formal connection between the memory kernel and the influence functions. We also show how approximate path integral methods can be understood in terms of approximate memory kernels. The insights we provide will significantly advance the understanding of non-Markovian dynamics.
  arXiv  Detail & Related papers  (2023-12-20T17:57:17Z)
• Theory of robust quantum many-body scars in long-range interacting systems [0.0]
  Quantum many-body scars (QMBS) are exceptional energy eigenstates of quantum many-body systems. We show that the setting of long-range interacting quantum spin systems generically hosts robust QMBS.
  arXiv  Detail & Related papers  (2023-09-21T22:00:40Z)
• Geometric phases along quantum trajectories [58.720142291102135]
  We study the distribution function of geometric phases in monitored quantum systems. For the single trajectory exhibiting no quantum jumps, a topological transition in the phase acquired after a cycle. For the same parameters, the density matrix does not show any interference.
  arXiv  Detail & Related papers  (2023-01-10T22:05:18Z)
• Quantum Transport in Open Spin Chains using Neural-Network Quantum States [11.137438870686026]
  We study the treatment of asymmetric open quantum systems with neural networks based on the restricted Boltzmann machine. In particular, we are interested in the non-equilibrium steady state current in the boundary-driven (anisotropic) Heisenberg spin chain.
  arXiv  Detail & Related papers  (2022-12-27T11:30:47Z)
• Visualizing spinon Fermi surfaces with time-dependent spectroscopy [62.997667081978825]
  We propose applying time-dependent photo-emission spectroscopy, an established tool in solid state systems, in cold atom quantum simulators. We show in exact diagonalization simulations of the one-dimensional $t-J$ model that the spinons start to populate previously unoccupied states in an effective band structure. The dependence of the spectral function on the time after the pump pulse reveals collective interactions among spinons.
  arXiv  Detail & Related papers  (2021-05-27T18:00:02Z)
• Sensing quantum chaos through the non-unitary geometric phase [62.997667081978825]
  We propose a decoherent mechanism for sensing quantum chaos. The chaotic nature of a many-body quantum system is sensed by studying the implications that the system produces in the long-time dynamics of a probe coupled to it.
  arXiv  Detail & Related papers  (2021-04-13T17:24:08Z)
• Spin Entanglement and Magnetic Competition via Long-range Interactions in Spinor Quantum Optical Lattices [62.997667081978825]
  We study the effects of cavity mediated long range magnetic interactions and optical lattices in ultracold matter. We find that global interactions modify the underlying magnetic character of the system while introducing competition scenarios. These allow new alternatives toward the design of robust mechanisms for quantum information purposes.
  arXiv  Detail & Related papers  (2020-11-16T08:03:44Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.