Paper-5 develops a reproducible symmetry-resolved method for analyzing the internal structure of fixed-order many-body quantum correlator fields using Johnson-harmonic decomposition. Instead of compressing a large collection of labelled correlators into a single overall number, the method keeps the subset structure of the data and separates the centered correlator field into different harmonic layers. This makes it possible to see how correlations are organized inside a quantum system, not only how large the total correlation is. J742_Paper5_Main_Manuscript_DOI… This work is part of the broader QDL five-paper progression: Paper-1 — Exact Permutation Moments: develops exact finite-sample mean, variance, and covariance formulas for Walsh interaction-order energies under permutation. Paper-2 — Exact Distribution Laws: extends the framework to structured exact distributions, Krawtchouk-based reductions, computational-complexity boundaries, and continuation-horizon classification. Paper-3 — Exact Certified Tail Computation: develops certified deterministic counting methods for difficult exact tail probabilities in a structured finite Walsh/Clebsch problem. Paper-4 — Identifiability, Contrast Closure, and Frozen External Testing: studies restricted four-variable log-linear interaction models, rank, identifiability, contrast closure, and a frozen external statistical test. Paper-5 — Johnson-Harmonic Correlator Profiles: applies a symmetry-resolved framework to complete labelled quantum correlator fields and studies how their internal correlation structure is distributed across Johnson-harmonic layers. The central challenge in Paper-5 is that a many-body experiment can produce hundreds or thousands of labelled correlators. If these are reduced to one aggregate norm, important structural information can be lost. Paper-5 preserves the full labelled subset geometry and resolves the correlator field into interpretable harmonic components. What Paper-5 does: reconstructs complete fixed-order labelled correlator fields from public experimental data; removes the common-mode component and decomposes the remaining structure into Johnson-harmonic layers; computes layer energies and normalized structural statistics; uses exact finite-population projector calibration; preserves subset-label information instead of reducing everything to a single total norm; propagates uncertainty using source-native randomized experimental replicates; applies an exact finite-shot bias correction to quadratic layer energies; compares the physical signal with a source-defined noise-reference cohort; provides a reproducible computational route through QDL Research Suite v1.3.0. The mathematical Johnson/slice decomposition itself is established mathematics; the contribution of Paper-5 is the combined experimental-analysis workflow and its application to two independent public quantum datasets. J742_Paper5_Main_Manuscript_DOI… Main locked results: For the six-qubit tomography dataset, each setting contains 20 three-body correlators with harmonic dimensions 20 = 1 + 5 + 9 + 5. Across 28 source measurement settings, the pooled centered correlation structure is: H1 = 48.4133% H2 = 36.7277% H3 = 14.8590% This shows a distributed harmonic profile rather than concentration in a single layer. J742_Paper5_Main_Manuscript_DOI… For the independent 32-qubit hardware dataset, each seed contains 4,960 three-body correlators, decomposed as 4,960 = 1 + 31 + 464 + 4,464. Across nine frozen seeds, the pooled profile is: H1 = 0.341937% H2 = 0.123369% H3 = 99.534694% showing an extremely strong H3-dominant structure. J742_Paper5_Main_Manuscript_DOI… The H3-dominant result remains stable across 675 source-randomized physical twirls. A seed-blocked bootstrap gives a pooled H3 95% interval of approximately: 99.5301% – 99.5388%. J742_Paper5_Main_Manuscript_DOI… After exact finite-shot correction, the pooled H3 fraction changes only from approximately 99.53469% → 99.53486%, showing that ordinary finite-shot sampling bias is extremely small relative to the observed structure. J742_Paper5_Main_Manuscript_DOI… A source-defined noise-renormalization reference cohort gives the opposite profile: Physical corrected H3: 99.534860% Noise-reference corrected H3: 0.138145% providing a strong diagnostic contrast between the physical cohort and the source-defined reference data. J742_Paper5_Main_Manuscript_DOI… How Paper-5 connects to the earlier papers:Paper-1 provides exact permutation-moment tools. Paper-2 studies structured exact distributions. Paper-3 develops certified exact-tail computation. Paper-4 focuses on identifiability and restricted interaction models. Paper-5 moves to a different but related application layer: it uses structured mathematical tools to analyze the internal organization of many-body quantum correlation fields. Why it is useful:The method is useful when a quantum experiment produces many labelled multi-qubit or many-body correlators and researchers want to understand where the structure is located inside that large correlation field. Potential applications include: quantum-state tomography; randomized-measurement analysis; many-body quantum experiments; multi-qubit correlation analysis; quantum-hardware characterization; comparison of correlation structures across devices or experiments; finite-shot robustness checks; structured analysis of subset-indexed data; reproducibility and independent verification of quantum experiments. Rather than asking only: “How much correlation is present?” Paper-5 also asks: “How is that correlation organized across different symmetry layers?” This makes the method useful as a structure scanner for complex quantum correlation data. Reproducibility:The computational implementation for Paper-5 is included in QDL Research Suite v1.3.0, DOI 10.5281/zenodo.22972830. The software provides the Paper-5 computational reproduction route while preserving the original public datasets as the source authority. J742_Paper5_Main_Manuscript_DOI… Paper-5 Preprint DOI:10.5281/zenodo.22974172 J742_Paper5_Main_Manuscript_DOI… Scope:Paper-5 provides a structural and statistical diagnostic workflow. The Johnson decomposition itself is established mathematics. The paper does not claim a new universal Johnson theorem, Bell nonlocality, neutrino thermalization from the H3 statistic, a new physical mechanism, causation, retrocausality, future-state prediction, or a nonzero physical intervention parameter. J742_Paper5_Main_Manuscript_DOI… In simple terms:Paper-5 takes a large set of quantum correlations and breaks it into meaningful symmetry layers. Instead of giving only one total correlation number, it shows where the correlation structure lives inside the data. In the six-qubit experiment, the structure is spread across several layers. In the 32-qubit dataset, almost all of the centered structure appears in the highest Johnson layer, and this pattern remains stable after randomized-twirl analysis and finite-shot correction. In one sentence:Paper-5 is a reproducible structure-analysis framework for complex quantum correlation data that shows not only how much correlation exists, but how that correlation is organized inside the system.
Paper-5 develops a reproducible symmetry-resolved method for analyzing the internal structure of fixed-order many-body quantum correlator fields using Johnson-harmonic decomposition. Instead of compressing a large collection of labelled correlators into a single overall number, the method keeps the subset structure of the data and separates the centered correlator field into different harmonic layers. This makes it possible to see how correlations are organized inside a quantum system, not only how large the total correlation is. J742_Paper5_Main_Manuscript_DOI… This work is part of the broader QDL five-paper progression: Paper-1 — Exact Permutation Moments: develops exact finite-sample mean, variance, and covariance formulas for Walsh interaction-order energies under permutation. Paper-2 — Exact Distribution Laws: extends the framework to structured exact distributions, Krawtchouk-based reductions, computational-complexity boundaries, and continuation-horizon classification. Paper-3 — Exact Certified Tail Computation: develops certified deterministic counting methods for difficult exact tail probabilities in a structured finite Walsh/Clebsch problem. Paper-4 — Identifiability, Contrast Closure, and Frozen External Testing: studies restricted four-variable log-linear interaction models, rank, identifiability, contrast closure, and a frozen external statistical test. Paper-5 — Johnson-Harmonic Correlator Profiles: applies a symmetry-resolved framework to complete labelled quantum correlator fields and studies how their internal correlation structure is distributed across Johnson-harmonic layers. The central challenge in Paper-5 is that a many-body experiment can produce hundreds or thousands of labelled correlators. If these are reduced to one aggregate norm, important structural information can be lost. Paper-5 preserves the full labelled subset geometry and resolves the correlator field into interpretable harmonic components. What Paper-5 does: reconstructs complete fixed-order labelled correlator fields from public experimental data; removes the common-mode component and decomposes the remaining structure into Johnson-harmonic layers; computes layer energies and normalized structural statistics; uses exact finite-population projector calibration; preserves subset-label information instead of reducing everything to a single total norm; propagates uncertainty using source-native randomized experimental replicates; applies an exact finite-shot bias correction to quadratic layer energies; compares the physical signal with a source-defined noise-reference cohort; provides a reproducible computational route through QDL Research Suite v1.3.0. The mathematical Johnson/slice decomposition itself is established mathematics; the contribution of Paper-5 is the combined experimental-analysis workflow and its application to two independent public quantum datasets. J742_Paper5_Main_Manuscript_DOI… Main locked results: For the six-qubit tomography dataset, each setting contains 20 three-body correlators with harmonic dimensions 20 = 1 + 5 + 9 + 5. Across 28 source measurement settings, the pooled centered correlation structure is: H1 = 48.4133% H2 = 36.7277% H3 = 14.8590% This shows a distributed harmonic profile rather than concentration in a single layer. J742_Paper5_Main_Manuscript_DOI… For the independent 32-qubit hardware dataset, each seed contains 4,960 three-body correlators, decomposed as 4,960 = 1 + 31 + 464 + 4,464. Across nine frozen seeds, the pooled profile is: H1 = 0.341937% H2 = 0.123369% H3 = 99.534694% showing an extremely strong H3-dominant structure. J742_Paper5_Main_Manuscript_DOI… The H3-dominant result remains stable across 675 source-randomized physical twirls. A seed-blocked bootstrap gives a pooled H3 95% interval of approximately: 99.5301% – 99.5388%. J742_Paper5_Main_Manuscript_DOI… After exact finite-shot correction, the pooled H3 fraction changes only from approximately 99.53469% → 99.53486%, showing that ordinary finite-shot sampling bias is extremely small relative to the observed structure. J742_Paper5_Main_Manuscript_DOI… A source-defined noise-renormalization reference cohort gives the opposite profile: Physical corrected H3: 99.534860% Noise-reference corrected H3: 0.138145% providing a strong diagnostic contrast between the physical cohort and the source-defined reference data. J742_Paper5_Main_Manuscript_DOI… How Paper-5 connects to the earlier papers:Paper-1 provides exact permutation-moment tools. Paper-2 studies structured exact distributions. Paper-3 develops certified exact-tail computation. Paper-4 focuses on identifiability and restricted interaction models. Paper-5 moves to a different but related application layer: it uses structured mathematical tools to analyze the internal organization of many-body quantum correlation fields. Why it is useful:The method is useful when a quantum experiment produces many labelled multi-qubit or many-body correlators and researchers want to understand where the structure is located inside that large correlation field. Potential applications include: quantum-state tomography; randomized-measurement analysis; many-body quantum experiments; multi-qubit correlation analysis; quantum-hardware characterization; comparison of correlation structures across devices or experiments; finite-shot robustness checks; structured analysis of subset-indexed data; reproducibility and independent verification of quantum experiments. Rather than asking only: “How much correlation is present?” Paper-5 also asks: “How is that correlation organized across different symmetry layers?” This makes the method useful as a structure scanner for complex quantum correlation data. Reproducibility:The computational implementation for Paper-5 is included in QDL Research Suite v1.3.0, DOI 10.5281/zenodo.22972830. The software provides the Paper-5 computational reproduction route while preserving the original public datasets as the source authority. J742_Paper5_Main_Manuscript_DOI… Paper-5 Preprint DOI:10.5281/zenodo.22974172 J742_Paper5_Main_Manuscript_DOI… Scope:Paper-5 provides a structural and statistical diagnostic workflow. The Johnson decomposition itself is established mathematics. The paper does not claim a new universal Johnson theorem, Bell nonlocality, neutrino thermalization from the H3 statistic, a new physical mechanism, causation, retrocausality, future-state prediction, or a nonzero physical intervention parameter. J742_Paper5_Main_Manuscript_DOI… In simple terms:Paper-5 takes a large set of quantum correlations and breaks it into meaningful symmetry layers. Instead of giving only one total correlation number, it shows where the correlation structure lives inside the data. In the six-qubit experiment, the structure is spread across several layers. In the 32-qubit dataset, almost all of the centered structure appears in the highest Johnson layer, and this pattern remains stable after randomized-twirl analysis and finite-shot correction. In one sentence:Paper-5 is a reproducible structure-analysis framework for complex quantum correlation data that shows not only how much correlation exists, but how that correlation is organized inside the system.
This preprint studies a structural failure mode in variational quantum mereology using the compact generalized-bipartition construction of Kabernik, Pollack, and Singh (KPS) as a benchmark. KPS previously reported non-uniqueness of the selected low-field structures, including six distinct state-reduction maps for the N=3 example. The contribution of this work is not the discovery of that degeneracy, but an explanation of its structural origin and its physical consequences.For finite open Ising chains, within the fixed computational-basis compact family, the diagonal Ising interaction does not contribute to the inter-row part of the short-time linear-entropy selector. As a result, the selector factorizes into a positive field-dependent normalization multiplied by a graph functional that is independent of the interaction ordering. This interaction blindness produces a criterion-symmetry surplus: the selector has a larger permutation symmetry than the discrete symmetry of the physical open-chain Hamiltonian.The mechanism is derived analytically, while its realization as physical non-identification is exhaustively certified for N=3, N=4, and N=5. The complete exact-selected sets contain 6, 48, and 120 compact maps, respectively, which split into 2, 12, and 30 discrete Hamiltonian-symmetry classes. An independent reduced-state information diagnostic varies across these classes, showing that structures considered equivalent by the selector can retain different physical information.For N=5, the exact selector optimum is 9/140. The full selected set contains 120 maps and 30 discrete Hamiltonian-symmetry classes, reproduced by independent exhaustive computational implementations. The accompanying reproducibility archive includes the manuscript, Supplemental Material, numerical certificates, symmetry audits, independent verification scripts, integrity manifests, and package-level reproducibility checks.An N=6 computational certificate is also included as a boundary check. It improves the certified loss bound to LOSS >= 51250 and gives the bracket 1232336 <= Z_F <= 1288670. This does not constitute closure of the exact N=6 optimum and is not used to claim an asymptotic scaling law.
A Reproducible Method for Checking Earlier Events and Later Choices in Quantum Experiments QDL Research Program — Paper 11 | Version V1.0.0 DOI: https://doi.org/10.5281/zenodo.23261100 Overview Quantum experiments can produce surprising results. Sometimes, an event is recorded first, and a measurement choice is made later. If these two events appear connected, an important question arises: Is this connection supported by the experimental data, or could it be explained by statistical variation, event selection, or measurement conditions? This paper presents a clear and reproducible method for investigating that question. It combines real experimental data, exact statistical calculations, source verification, and computer-based testing. The main goal is simple: make quantum-data calculations easier to understand, repeat, and independently check. What Does This Paper Study? The study examines how researchers can correctly compare an earlier recorded event with a later measurement setting. It focuses on five important questions: Were the earlier events and later settings correctly identified? Were all eligible events included using the original experimental rules? Do the observed numbers show a meaningful statistical relationship? Could selection effects, detection differences, or data-matching errors explain the result? Can another researcher reproduce the same calculations using the available sources? The paper provides mathematical formulas, numerical examples, source checks, and reproducible software for these questions. Three Main Research Applications 1. Munich Event-Ready Bell Experiment The first application studies data from a published quantum Bell experiment involving entangled atoms. The published dataset contains 55,568 events. We independently recalculated four-sector statistics from the published count tables. The main results are: Measurement Odds Ratio Fisher p-value Lab 1 0.997122 0.8653 Lab 2 0.980578 0.2486 These results do not provide stable evidence of an association between the selected variables in the full published counts. We also analyzed original event-level records from two experimental runs in April and June 2016. These files contain 20,403 valid paired events. By applying the original selection rule of 5,000 events per Bell-state class, we exactly reproduced the historical results. All 16 published sector counts matched, with zero differences. This demonstrates why correct event selection and source verification are important for reliable scientific calculations. 2. Photonic Quantum-Switch Experiment The second application examines published data from a 2026 photonic quantum-switch experiment. The original study reported a Bell-like causal-inequality value of approximately 1.8090 ± 0.0024, compared with a fixed-order bound of 1.75. We independently recalculated the relevant quantity using 256 published probability entries. Our calculated value was: 1.808954375 This agrees with the reported result at its published precision. We also examined six statistical comparisons involving measurement settings and marginal probabilities. These checks help distinguish an experimental causal-inequality result from a possible statistical relationship between an earlier event and a later setting. The two questions are different and should not be confused. 3. Testing the Method with 80,000 Synthetic Trials The third application uses 80,000 computer-generated trials, divided into four controlled scenarios. The scenarios represent: A system with no inserted effect. A system with a deliberately inserted statistical difference. A system affected by detection-efficiency differences. A system with information leakage before the earlier result was fully recorded. The software reproduced the expected numerical results for all four scenarios. These tests show how the method can identify known statistical patterns and distinguish them from possible experimental artifacts. The synthetic trials are software-validation data, not new laboratory observations. Main Contributions This paper brings together several important elements in one reproducible research workflow. 1. Clear event identification It defines which event happened earlier, which setting was chosen later, and how the records should be matched. 2. Exact statistical calculations It uses four-sector count tables, odds ratios, log-affinity measures, uncertainty estimates, and Fisher's exact tests. 3. Original-data verification It demonstrates how the correct historical event-selection rule can reproduce published results exactly. 4. Independent source comparisons It uses different quantum datasets without incorrectly treating their measurements as equivalent. 5. Reproducible software It provides a computational framework for repeating the calculations, checking results, and recording source limitations. Why Is This Work Useful? Scientific results become more valuable when other researchers can independently verify them. This paper offers a practical way to investigate complex quantum-data questions without depending only on interpretations or assumptions. The method can help researchers: Recheck published quantum experiments. Find problems caused by event selection or data matching. Compare statistical results across experimental runs. Separate real experimental measurements from simulated examples. Design more reliable tests for future quantum experiments. Understand which conclusions are supported by the available evidence. Scientific Scope This work is primarily about statistical verification, experimental-data interpretation, and reproducibility. It does not establish backwards-time signalling or a new fundamental physical law. The Munich published-count analysis and the two recovered original runs have different levels of source access. The quantum-switch experiment measures a different physical quantity. The synthetic trials are used only to test the software. These distinctions are maintained throughout the study. Data and Software Availability The calculations are supported by QDL Research Suite, a Python-based scientific software package containing tools for reproducible mathematical and statistical analysis. QDL Research Suite — All Versions: https://doi.org/10.5281/zenodo.22952901 QDL Research Suite v1.10.0 — Version Used: https://doi.org/10.5281/zenodo.23256494 The software provides calculation modules, reproducibility tools, automated tests, and verification outputs. The study also identifies the original experimental publications and available source datasets so that the calculations can be checked against their sources. Conclusion The central contribution of Paper 11 is a clear, source-linked method for checking quantum experimental data. It combines published experimental results, original event records, exact statistical methods, and controlled software tests. The work shows how careful data selection, transparent calculations, and independent verification can improve confidence in scientific analysis. Its purpose is to help make complex quantum research more understandable, reproducible, and reliable, while keeping mathematical results, experimental evidence, and physical interpretations clearly separated. Author: Roshankumar Chandaliya Research Program: Quantum Diverter Loop (QDL) Paper: 11 Version: V1.0.0 DOI: https://doi.org/10.5281/zenodo.23261100
Quantum correlations are a fundamental property of quantum many-body states. Yet they remain experimentally elusive, hindering certification of genuine quantum behavior, especially in quantum materials. Here we show that the momentum-dependent dynamical susceptibility measured via inelastic neutron scattering enables the systematic reconstruction of a general family of quantum correlation functions, which express the degree of quantum coherence in the fluctuations of two spins at an arbitrary mutual distance. Using neutron scattering data for the compound KCuF 3 —a system of weakly coupled S = 1 / 2 Heisenberg chains—and numerically exact quantum Monte Carlo data, we show that quantum correlations possess a radically different spatial structure with respect to conventional correlations. Indeed, they exhibit a different emergent length scale—the quantum coherence length—which is finite at any finite temperature (including when long-range magnetic order develops). Moreover, we show theoretically that coupled Heisenberg spin chains exhibit a form of quantum monogamy, with a trade-off between quantum correlations along and transverse to the spin chains. These results highlight real-space quantum correlators as an informative, model-independent means of probing the underlying quantum state of real quantum materials. Published by the American Physical Society 2024
A two-mode quantum harmonic oscillator is reconstructed from the axiom that a single distinction is the primitive degree of freedom. The construction forces an internal reference witness, Euclidean geometry and a positive irrational remainder δ=2−1. The binary count remains I=1, while its complete account retains the identifying relations and succession that the count alone omits. Symmetry conservation and recoverable closure establish persistence, with a next lawful step always available. Circular closure supplies the exact area increment g=(π−2)/4. Its accumulation forces escapement: an additional complete unit is admitted with its witness and origin retained. Applying the primitive construction to this unit supplies the joint Archimedes trammel and its three-dimensional family. The completion event fixes the relative phase and recoverable shadow amplitudes. Subsequent comparisons complete the cell account, whose positive irrational remainder Ω=1−π/(32) permits further admission. Representing complete accumulated area as squared ladder weight uniquely fixes wn2=(n+1)g and the dimensionless action coefficient ℏ∗=g. Source and child quadratures satisfy the canonical relations on a common invariant domain. At escapement, the completed-unit contribution restores the commutator term missing from the source remainder. The Hamiltonian Htick=(πℏ∗/2)(nα+nβ+Id) has a complete discrete spectrum; ni counts oscillator occupations. Its unitary evolution reproduces the trammel's quarter-turn, and an explicit Hermite transform supplies the equivalent Schrödinger representation. The geometric birth comparison becomes an entangled source–child state. Its complete amplitudes and retained context recover the producing account. Each finite generated retained history admits a faithful quantum memory representation satisfying structural record coherence with sequential weak value one.
Paper 9 - Exact General-d Affinity Reversal and Contrast-Space Invariants introduces a compact mathematical framework for understanding a simple but important question: When an interaction is reversed, what changes, what stays the same, and how can that be measured exactly? The paper extends binary affinity to general d-state systems, derives an exact reversal law, and introduces the transformed coordinate Ξd, for which reversal becomes especially simple: ΞR=−ΞF. It also identifies reversal-stable quantities and extends the analysis from a single scalar to the full interaction matrix Θ=HTln(Z)H, allowing richer multi-state structure to be studied through singular values, rank, interaction strength, determinant magnitude, and effective participation. Exact_General_d_Affinity_Revers… Exact_General_d_Affinity_Revers… Why it is useful: the framework can help researchers compare forward and reversed interaction descriptions, study systems with more than two states, test whether a single summary is sufficient, and identify stable geometric features in complex interaction data. The paper includes qutrit, qubit, and many-body validation examples to demonstrate how the method can be used in practice. Exact_General_d_Affinity_Revers… Connected QDL Research This work is part of the broader Quantum Diverter Loop (QDL) research program. Earlier QDL papers develop complementary tools for exact permutation analysis, exact counting and tail probabilities, model identifiability, higher-order interactions, cumulant response, multimode affinity geometry, causal testing, and binary affinity analysis. The methods from Papers 1–9, together with compatibility support for Papers 17–19, are organized in the reproducible QDL Research Suite v1.8.0, making the calculations easier to repeat, test, compare, and independently verify. QDL Research Suite v1.8.0:DOI: 10.5281/zenodo.23161137 All QDL Research Suite versions:DOI: 10.5281/zenodo.22952901 In simple terms, this paper adds a new multi-state reversal layer to a growing QDL toolkit for exact mathematics, reproducible computation, interaction analysis, and independent verification.
As Schroedinger already recognised one century ago, entanglement is at the core of quantum mechanics. Nowadays it turns out to be the fundamental notion behind many quantum phenomena, from quantum algorithms to gravity, passing by critical phenomena and topological phases of matter, triggering unexpected connections between apparently far branches of physics. At the center of all these ideas, we find the (Rényi) entanglement entropies, which are powerful entanglement measures that provide fundamental insights into the investigated system or theory. This motivates the development of techniques for determining it, such as the replica trick: its implementation via the path-integral finds a wide place in this thesis. For example, we develop an efficient strategy to compute a generalised version of the Rényi entropies for all the eigenstates of a (1+1)-dimensional conformal field theory. This represents the starting point for a simulation scheme ideal to compute the entanglement in more generic (1+1)-dimensional quantum field theories (QFTs), e.g. after a quench in the sine-Gordon field theory. The study of entanglement also intertwines with another pillar of modern physics, i.e. symmetries and how their presence influences the properties of a system. Given the interest in this connection, this thesis addresses the question of how the entanglement splits into the different sectors of an internal symmetry. We approach the problem first in the QFT context, both for the free Dirac and complex scalar fields in two-dimensional spacetime, which have an abelian conserved charge, and systems having an internal Lie group symmetry to tackle the non-abelian case. Another typical framework in which we study the symmetry resolution of entanglement is lattice models, where different techniques can be exploited in order to derive exact results, ranging from the corner transfer matrix for gapped integrable systems to the connection between quadratic lattice Hamiltonians and their two-point correlation functions. The symmetry resolution also concerns other entanglement measures, namely, we analyse the behaviour of the operator entanglement, i.e. a key quantifier of the complexity of an operator, the symmetry-resolved mutual information, the effect of symmetries on entanglement negativity. The latter quantity is a genuine measure of quantum correlations in mixed states and a consistent part of the thesis is about this subject. For example, we study its time evolution after a quench and we provide an operatorial characterisation for entanglement in mixed states, which we dub negativity Hamiltonian.