Measuring unconventional causal structures in monitored dynamics

• URL: http://arxiv.org/abs/2601.12271v1
• Date: Sun, 18 Jan 2026 05:58:19 GMT
• Title: Measuring unconventional causal structures in monitored dynamics
• Authors: Hong-Yi Wang, Haifeng Tang, Xiao-Liang Qi,
• Abstract summary: We study the causal structure and emergent "arrow of time" in monitored quantum dynamics.<n>We propose a new measure, the cross-entropy quantum causal influence, to quantify the extent of causal influence.
• Score: 7.280769022083202
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Causality underpins all logical reasoning. However, the causal structure in quantum processes can be far from intuitive, often differing from its classical counterpart in relativity, which is defined by the light cone. In particular, in systems with measurement and post-selection, causal influence can occur between spacelike separated regions. In this work, we study the causal structure and emergent "arrow of time" in monitored quantum dynamics, particularly their dependence on initial and final states. We propose a new measure, the cross-entropy quantum causal influence, to quantify the extent of causal influence, whose simulation demonstrates exotic causal structures, such as inverted light cones. This quantity can be measured in current quantum computing platforms. Additionally, we provide an analytical understanding of the relation between time arrow and entropy by studying two types of models that are analytically tractable: a quantum Brownian evolution model and a dual-unitary circuit model.

Related papers

• Measurement-induced crossover in quantum first-detection times [39.98742834565653]
  We show that the measurement back action intrinsic to quantum mechanics may profoundly alter the system dynamics.<n>For a quantum particle in one spatial dimension subject to stroboscopic measurements, we observe an algebraic decay of the probability of the first-detection time if the particle is free.<n>This crossover reflects the purely quantum nature of the detection process, which fundamentally distinguishes it from the first-passage problem in classical systems.
  arXiv  Detail & Related papers  (2026-01-17T16:48:07Z)
• Direct probing of the simulation complexity of open quantum many-body dynamics [42.085941481155295]
  We study the role of dissipation in simulating open-system dynamics using both quantum and classical methods.<n>Our results show that dissipation affects correlation length and mixing time in distinct ways at intermediate and long timescales.
  arXiv  Detail & Related papers  (2025-08-27T15:14:36Z)
• Conditional mutual information: A generalization of causal inference in quantum systems [3.401200772945481]
  We develop a quantum causal index, tailored to learn the causal relationships inherent in quantum systems.<n>Our study focuses on the asymmetric quantum conditional mutual information (QCMI), incorporating the von Neumann entropy.<n>We study the effective causal propagation velocity, which is the speed at which QCMI becomes significant at distant sites.
  arXiv  Detail & Related papers  (2025-08-16T20:50:53Z)
• Probing Quantum States Over Spacetime Through Interferometry [4.437382576172235]
  We establish a notion of the quantum state that applies consistently across space and time.<n>We show that measurements can always be implemented with interferometry.<n>We show that our formalism reveals a new type oftemporal correlation between two quantum dynamics.
  arXiv  Detail & Related papers  (2025-07-25T13:36:01Z)
• Theory of the correlated quantum Zeno effect in a monitored qubit dimer [41.94295877935867]
  We show how the competition between two measurement processes give rise to two distinct Quantum Zeno (QZ) regimes.<n>We develop a theory based on a Gutzwiller ansatz for the wavefunction that is able to capture the structure of the Hilbert phase diagram.<n>We show how the two QZ regimes are intimately connected to the topology of the flow of the underlying non-Hermitian Hamiltonian governing the no-click evolution.
  arXiv  Detail & Related papers  (2025-03-28T19:44:48Z)
• Experimental demonstration of quantum causal inference via noninvasive measurements [2.649823756203203]
  We probe whether causal structure can be determined without intervention in quantum systems. We demonstrate the experimental discrimination between several possible causal structures for a bipartite quantum system at two times.
  arXiv  Detail & Related papers  (2024-11-09T03:29:44Z)
• Enhanced Entanglement in the Measurement-Altered Quantum Ising Chain [43.80709028066351]
  Local quantum measurements do not simply disentangle degrees of freedom, but may actually strengthen the entanglement in the system.<n>This paper explores how a finite density of local measurement modifies a given state's entanglement structure.
  arXiv  Detail & Related papers  (2023-10-04T09:51:00Z)
• Quantum Causal Inference with Extremely Light Touch [0.0]
  We give a causal inference scheme using quantum observations alone for a case with both temporal and spatial correlations.<n>The protocol determines compatibility with 5 causal structures distinguished by the direction of causal influence.
  arXiv  Detail & Related papers  (2023-03-19T02:59:05Z)
• Universality of critical dynamics with finite entanglement [68.8204255655161]
  We study how low-energy dynamics of quantum systems near criticality are modified by finite entanglement. Our result establishes the precise role played by entanglement in time-dependent critical phenomena.
  arXiv  Detail & Related papers  (2023-01-23T19:23:54Z)
• Admissible Causal Structures and Correlations [0.0]
  We study limitations on causal structures and correlations imposed by local quantum theory. For one, we find a necessary graph theoretic criterion--the "siblings-on-cycles" property--for a causal structure to be admissible. We show that these causal models, in a restricted setting, are indeed consistent.
  arXiv  Detail & Related papers  (2022-10-23T17:33:47Z)
• Efficient Distinction between Quantum Direct and Common Causes and its Experimental Verification [15.082156478846654]
  We introduce a quantity named Causal Determinant' to efficiently identify the quantum causal structures between two quantum systems. According to the causal determinant, the quantum direct cause imposed by an arbitrary unitary operator can be perfectly discriminated with the quantum common cause.
  arXiv  Detail & Related papers  (2022-03-05T14:12:37Z)
• Unification of Random Dynamical Decoupling and the Quantum Zeno Effect [68.8204255655161]
  We show that the system dynamics under random dynamical decoupling converges to a unitary with a decoupling error that characteristically depends on the convergence speed of the Zeno limit. This reveals a unification of the random dynamical decoupling and the quantum Zeno effect.
  arXiv  Detail & Related papers  (2021-12-08T11:41:38Z)
• Unraveling the topology of dissipative quantum systems [58.720142291102135]
  We discuss topology in dissipative quantum systems from the perspective of quantum trajectories. We show for a broad family of translation-invariant collapse models that the set of dark state-inducing Hamiltonians imposes a nontrivial topological structure on the space of Hamiltonians.
  arXiv  Detail & Related papers  (2020-07-12T11:26:02Z)

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.