Leggett-Garg Inequality Violations Bound Quantum Fisher Information

• URL: http://arxiv.org/abs/2604.09772v1
• Date: Fri, 10 Apr 2026 18:00:34 GMT
• Title: Leggett-Garg Inequality Violations Bound Quantum Fisher Information
• Abstract summary: We prove that a violation of a Leggett-Garg inequality for bounded observables in stationary pure states and thermal states yields a rigorous lower bound on the quantum Fisher information.<n>We show that temporal correlations of a single collective observable can serve as an experimentally accessible witness of many-body quantum coherence.
• Score: 0.07777489763207261
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: We prove that a violation of a Leggett-Garg inequality for bounded observables in stationary pure states and thermal states yields a rigorous lower bound on the quantum Fisher information. This turns a qualitative foundations test of realism in quantum systems into a quantitative witness of useful quantum sensitivity and, in the collective setting, into a lower bound on multipartite entanglement depth in many-body systems. We further demonstrate that Leggett-Garg violations are constrained by the same spectral moments, susceptibilities, and $f$-sum-rule bounds that organize many-body response. Our results show that temporal correlations of a single collective observable can serve as an experimentally accessible witness of many-body quantum coherence, without requiring full state reconstruction.

Related papers

• Hysteretic squashed entanglement in many-body quantum systems [42.085941481155295]
  Entanglement in many-body quantum systems is distributed across spatial regions.<n>We propose hysteretic entanglement $T_sq$, a conditional entanglement that measures the genuine quantum correlations between two subregions.<n>We show that $T_sq$ can detect genuine quantum correlations across both adjacent and long-range subsystems.
  arXiv  Detail & Related papers  (2026-03-10T17:00:49Z)
• Detecting unfaithful entanglement by multiple fidelities [7.320365821066744]
  Certifying entanglement for unknown quantum states experimentally is a fundamental problem in quantum computing and quantum physics. Because of being easy to implement, a most popular approach for this problem in modern quantum experiments is detecting target quantum states with fidelity-based entanglement witnesses. Recently, it has been realized that there exist so-called unfaithful quantum states, which can be entangled, but their entanglement cannot be certified by any fidelity-based entanglement witnesses.
  arXiv  Detail & Related papers  (2024-09-20T04:58:12Z)
• Quantum Non-Demolition Measurements and Leggett-Garg inequality [0.0]
  Quantum non-demolition measurements define a non-invasive protocol to extract information from a quantum system. This protocol leads to a quasi-probability distribution for the measured observable outcomes, which can be negative. We show that there are situations in which Leggett-Garg inequalities are satisfied even if the macrorealism condition is violated.
  arXiv  Detail & Related papers  (2024-07-31T18:04:51Z)
• Ergodiscord: An Operational and Distinct Notion of Quantumness of Correlations [0.0]
  We present a framework for exploring quantumness of correlations in multipartite quantum states.<n>We introduce an operational quantifier of nonclassicality, termed em ergodiscord.<n>We show that a mixed nonclassical state can lock more work than the maximally entangled state of the corresponding system.
  arXiv  Detail & Related papers  (2024-07-11T08:38:51Z)
• 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)
• High-dimensional monitoring and the emergence of realism via multiple observers [41.94295877935867]
  Correlation is the basic mechanism of every measurement model.<n>We introduce a model that interpolates between weak and strong non-selective measurements for qudits.
  arXiv  Detail & Related papers  (2023-05-13T13:42:19Z)
• Overlapping qubits from non-isometric maps and de Sitter tensor networks [41.94295877935867]
  We show that processes in local effective theories can be spoofed with a quantum system with fewer degrees of freedom. We highlight how approximate overlapping qubits are conceptually connected to Hilbert space dimension verification, degree-of-freedom counting in black holes and holography.
  arXiv  Detail & Related papers  (2023-04-05T18:08:30Z)
• Witnessing the non-objectivity of an unknown quantum dynamics [0.6745502291821955]
  We show that objectivity implies a Bell-like inequality. Observers probing distinct parts of the environment can agree upon their measurement outcome of a given observable. But such outcome can be totally uncorrelated from the property of the quantum system that fixed observable should be probing.
  arXiv  Detail & Related papers  (2022-11-28T18:44:42Z)
• Improved Quantum Algorithms for Fidelity Estimation [77.34726150561087]
  We develop new and efficient quantum algorithms for fidelity estimation with provable performance guarantees. Our algorithms use advanced quantum linear algebra techniques, such as the quantum singular value transformation. We prove that fidelity estimation to any non-trivial constant additive accuracy is hard in general.
  arXiv  Detail & Related papers  (2022-03-30T02:02:16Z)
• Experimental violations of Leggett-Garg's inequalities on a quantum computer [77.34726150561087]
  We experimentally observe the violations of Leggett-Garg-Bell's inequalities on single and multi-qubit systems. Our analysis highlights the limits of nowadays quantum platforms, showing that the above-mentioned correlation functions deviate from theoretical prediction as the number of qubits and the depth of the circuit grow.
  arXiv  Detail & Related papers  (2021-09-06T14:35:15Z)
• Unveiling quantum entanglement in many-body systems from partial information [0.0]
  This paper introduces a flexible data-driven entanglement detection technique for uncharacterized quantum many-body states. It is of immediate relevance to experiments in a quantum advantage regime.
  arXiv  Detail & Related papers  (2021-07-08T16:17:02Z)
• Einselection from incompatible decoherence channels [62.997667081978825]
  We analyze an open quantum dynamics inspired by CQED experiments with two non-commuting Lindblad operators. We show that Fock states remain the most robust states to decoherence up to a critical coupling.
  arXiv  Detail & Related papers  (2020-01-29T14:15:19Z)

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.