arXiv subjects

Rachid Ahl Laamara

Publications and source records attributed to Rachid Ahl Laamara.

At least 37 records · Page 2Linked to original sources

arXiv2026

Multiparameter quantum estimation and entanglement in top--antitop quark production

We investigate the interplay between quantum correlations and multiparameter quantum estimation in top--antitop quark pair production through the gluon-fusion channel. Using the spin density matrix formalism, we construct an effective two-qubit quantum state governed by the relativistic parameters associated with the scattering process. Within the framework of quantum metrology, we derive the quantum Fisher information matrix for the simultaneous estimation of the relativistic velocity parameter and the production angle, and we analyze the corresponding quantum precision bounds. Our results reveal highly nontrivial estimation regimes strongly controlled by relativistic spin correlations and scattering geometry. We further characterize the produced state through the concurrence and demonstrate the existence of strong connections between entanglement structures and multiparameter estimation sensitivity. Finally, we discuss the experimental feasibility of probing these effects at the Large Hadron Collider through spin-correlation observables and reconstructed top--antitop density matrices. Our results identify top--antitop production as a unique relativistic platform for exploring quantum information theory and multiparameter quantum metrology in high-energy physics.

quant-ph↗

arXiv2026

Quantum unital Otto heat engines: using Kirkwood-Dirac quasi-probability for the engine's coherence to stay alive

In this work, we consider quantum unital Otto heat engines. The latter refers to the fact that both the unitaries of the adiabatic strokes and the source of the heat provided to the engine preserve the maximally mixed state. We show how to compute the cumulants of either the dephased or undephased engine. For a qubit, we give the analytical expressions of the averages and variances for arbitrary unitaries and unital channels. We do a detailed comparative study between the dephased and undephased heat engines. More precisely, we focus on the effect of the parameters on the average work and its reliability and efficiency. As a case study of unital channels, we consider a quantum projective measurement. We show on which basis we should projectively measure the qubit, either the dephased or undephased heat engine, to extract higher amounts of work, increase the latter's reliability, and increase efficiency. Further, we show that non-adiabatic transitions are not always detrimental to thermodynamic quantities. Our results, we believe, are important for heat engines fueled by quantum measurement.

quant-ph↗

arXiv2026

Characterizing quantum correlations and quantum teleportation in $gg \to t\bar{t}$ and $q\bar{q} \to t\bar{t}$ processes under noisy channels

The measurement of top-quark spin correlations provides a key tool for probing its interactions with high precision. Owing to its extremely short lifetime ($τ\sim 10^{-25}$ s), the top quark preserves its spin polarization information, making the $t\bar{t}$ system an ideal framework for investigating quantum correlations in high-energy physics. In this work, we analyze quantum correlations in $t\bar{t}$ pairs produced in QCD using several quantum information-theoretic measures, including Bell nonlocality, quantum steering, concurrence, and geometric quantum discord. Their dependence on kinematic variables is examined in both the $gg \to t\bar{t}$ and $q\bar{q} \to t\bar{t}$ channels, with convergence toward the $gg \to t\bar{t}$ dominated regime in the ultra-relativistic limit ($β= 1$). We also investigate the effect of three effective decoherence channels (AD, PD, and PF). The AD and PD channels lead to a monotonic degradation of correlations as the decoherence parameter $p$ increases, while the PF channel exhibits a symmetric behavior around $p=1/2$. The impact of these channels on quantum teleportation is analyzed, showing that it remains above the classical threshold of $2/3$ even in the presence of noise. These results indicate that certain quantum resources can persist despite decoherence, opening new perspectives at the interface of quantum information and particle physics.

quant-ph↗

arXiv2026

Dephasing Effects on the Dynamical Evolution of Quantum Correlations and Coherence in Neutrino Oscillations

Neutrino oscillations confirm the presence of mode entanglement, as each flavor eigenstate is composed of a coherent superposition of distinct mass eigenstates. In this work, we investigate the dynamics of quantum resources in neutrino oscillation systems by analyzing quantum steering, logarithmic negativity, and quantum coherence within a two-flavor framework. Treating neutrino oscillations as an effective two-level quantum system, we study the influence of environmental decoherence on these nonclassical features by modeling the system as an open quantum system. Three representative noise channels are considered, namely amplitude damping (AD), phase flip (PF), and phase damping (PD), allowing us to capture both dissipative and dephasing mechanisms. We examine the evolution of quantum resources in both Markovian and non-Markovian regimes, highlighting the role of memory effects in the system-environment interaction. The results reveal a clear hierarchy in the robustness of quantum resources under decoherence. Steering is the most sensitive correlation in the hierarchy under decoherence effects. while logarithmic negativity exhibits intermediate robustness. Quantum coherence displays the highest resilience, persisting over a wider range of parameters. In the PF and PD channels, logarithmic negativity and coherence are shown to exhibit identical dynamical behavior, reflecting their common dependence on phase-related noise. In contrast, the non-Markovian regime leads to delayed decoherence and partial revivals of entanglement and coherence due to information backflow, whereas quantum steering remains strongly suppressed. These findings provide a comparison of different quantum resources in neutrino oscillation systems and offer new insights into the interplay between decoherence mechanisms and quantum correlations.

quant-ph↗

arXiv2026

Entanglement and Quantum Coherence in Coupled Double Quantum Dots under Markovian and Non-Markovian Noisy Channels

Quantum dots are nanometer-scale semiconductor particles that exhibit size-dependent quantum mechanical properties. In this work, we investigate the dynamics of quantum correlations, quantified by the concurrence and the quantum coherence, in a bipartite system of coupled double quantum dots. The analysis is carried out within both Markovian and non-Markovian regimes, and further extended to different noisy quantum channels, including amplitude damping, phase flip, and phase damping. Our results show that environmental memory plays a crucial role in the preservation of quantum correlations, leading to oscillatory behavior and partial revivals in the non-Markovian regime, in contrast to the monotonic decay observed under Markovian dynamics. Moreover, distinct decoherence mechanisms induce qualitatively different effects: dissipative channels rapidly suppress correlations, while phase-based channels lead to either redistribution or gradual degradation. A key finding is that quantum coherence exhibits a higher robustness compared to entanglement under all considered conditions, highlighting its relevance as a reliable quantum resource in noisy environments. These results provide valuable insights into the control and protection of quantum correlations in realistic solid-state systems.

quant-ph↗

arXiv2026

Mass-correction-induced enhancement of quantum correlations even beyond entanglement in the $e^{+}e^{-} \rightarrow J/ψ\rightarrow Λ(pπ^{-}) \barΛ(\bar{p}π^{+})$ process at the BESIII experiment under memory effects

In this work, we derive the bipartite density matrix for the $e^{+}e^{-} \rightarrow J/ψ\rightarrow Λ(pπ^{-}) \barΛ(\bar{p}π^{+})$ process at BESIII. We evaluate the impact of mass corrections and memory effects (within Markovian and non-Markovian regimes) on quantum correlations even beyond entanglement. The dependence of these quantum properties on the scattering angle $φ$ is analyzed, with a particular focus on the impact of mass corrections. By comparing massless and mass-corrected scenarios, we demonstrate that the inclusion of mass effects enhances the maximum violation of the Bell inequality. While the qualitative temporal behavior remains unchanged, mass corrections quantitatively modify the angular distribution and introduce additional extrema at $φ=0$ and $φ=π$, thereby strengthening non-local correlations without altering their fundamental dynamical origin. An examination of the hierarchy of quantum correlations in baryon-antibaryon systems yields partial confirmation: $\text{Bell Nonlocality} \subset \text{Steering} \subset \text{Entanglement} \subset \text{Discord}$. Additionally, our results show that classical correlations serve to mitigate the decoherence and the decay of quantum correlations. This interplay between classical and quantum correlations suggests practical applications in quantum information and provides a robust framework for investigating baryon-antibaryon interactions.

quant-ph↗

arXiv2026

Multiparameter quantum estimation and Stirling Engine Performance in a Gravitational Cat State System

We investigate the multiparameter quantum estimation and quantum thermodynamics properties of a gravitational cat state (gravcat) system composed of two interacting massive particles confined in double-well potentials. The system is described by an effective Hamiltonian involving the energy splitting parameter $ω$ and the gravitational coupling strength $γ$, while the interaction with a thermal environment is modeled through a Gibbs thermal state. Within the framework of quantum parameter estimation theory, we employ the quantum Fisher information matrix (QFIM) to analyze the precision limits for estimating the three fundamental parameters of the model, namely the gravitational coupling $γ$, the energy splitting $ω$, and the temperature $T$. Utilizing the symmetric logarithmic derivative (SLD) formalism within the QFIM framework, we derive the analytical expressions of the estimation bounds and evaluate the corresponding minimal variances associated with the quantum Cramér-Rao bound. Both simultaneous and individual estimation strategies are investigated, and their performances are compared in different parameter regimes. Our results reveal the existence of optimal estimation regions where the precision is significantly enhanced and show that the relative efficiency of the estimation schemes strongly depends on the interaction strength, the energy gap, and the thermal environment. In addition, the thermodynamic behavior of the system is analyzed within the framework of a quantum Stirling cycle. The internal energy, entropy, heat exchanges, and work production are examined, allowing us to evaluate the efficiency of the gravcat-based quantum heat engine. The obtained results highlight the interplay between quantum metrology and quantum thermodynamics.

quant-ph↗

arXiv2026

Optimal multiparameter quantum estimation in accelerating Unruh-DeWitt detectors

The quantum Fisher information matrix (QFIM) is central to multiparameter quantum metrology, dictating the attainable sensitivity via the quantum Cramér-Rao bound. In this work, we investigate the ultimate precision limits for relativistic quantum thermometry in a bipartite system of uniformly accelerated Unruh-DeWitt detectors. Utilizing the symmetric logarithmic derivative (SLD) formalism within the QFIM framework, we analyze the individual and simultaneous estimation of the Unruh temperature $T$ and the initial-state parameter $Δ_0$. In the noiseless case, we demonstrate that these two parameters are quantum compatible, allowing the multiparameter quantum Cramér-Rao bound to be saturated without a loss of precision. We then examine the impact of environmental effects by comparing Markovian and non-Markovian dynamics. In the Markovian regime, dissipation leads to a monotonic degradation of estimation precision; conversely, non-Markovian memory effects induce temporal oscillations and transient precision enhancements due to information backflow. The robustness of the estimation protocols is further analyzed under correlated noisy channels, including amplitude damping, phase flip, and phase damping. We show that dissipative noise results in more significant precision loss than purely dephasing mechanisms, whereas classical correlations in the noise mitigate this degradation. Finally, we discuss the estimation of the detector energy-level spacing $ω$ as a natural extension, highlighting its sensitivity to the environmental structure. Our results provide a unified framework for relativistic multiparameter quantum metrology within the context of open quantum systems.

quant-ph↗

arXiv2026

Enhanced multiparameter quantum estimation in cavity magnomechanics via a coherent feedback loop

Multiparameter quantum metrology plays a fundamental role in uncovering and exploiting the distinctive features of quantum systems. In this work, we propose an effective and experimentally feasible scheme to significantly enhance the simultaneous quantum estimation of the photon magnon and magnon mechanical coupling strengths in a hybrid cavity magnon mechanical platform. Our approach relies on the assistance of a coherent feedback loop combined with the injection of a coherent driving field. We show that an appropriate tuning of the system and feedback parameters leads to a substantial reduction of the estimation errors associated with both coupling strengths. To quantify the metrological performance of the proposed scheme, we employ the quantum Cramer Rao bound (QCRB) as a fundamental benchmark for multiparameter estimation. We explicitly compute and compare the QCRBs derived from the symmetric logarithmic derivative (SLD) and the right logarithmic derivative (RLD) formalisms. Our results demonstrate that the RLD based QCRB is systematically lower than the SLD based bound, indicating superior estimation precision in the considered noncommutative estimation scenario. We further analyze the performance of heterodyne detection and show that, in suitable parameter regimes, the corresponding classical estimation precision closely approaches the ultimate quantum limit predicted by our scheme. Finally, we discuss the experimental feasibility of the proposed setup within currently available cavity magnon mechanical platforms. Owing to its general character, the framework developed here can be readily extended to the high precision estimation of other physical parameters in hybrid quantum systems.

quant-ph↗

arXiv2026

Squeezed-Light-Enhanced Multiparameter Quantum Estimation in Cavity Magnonics

Improving multiparameter quantum estimation in magnonic systems via quantum noise suppression is a well-established and critical research objective. In this work, we propose an experimentally realistic scheme to improve the precision of simultaneously estimating different parameters in a cavity-magnon system by utilizing a degenerate optical parametric amplifier (OPA). The OPA enhances the estimation precision by decreasing the most informative quantum Cramér-Rao bound, calculated employing the symmetric logarithmic derivative (SLD) and the right logarithmic derivative (RLD). We show that when nonlinearity is introduced into the system, quantum noise is significantly suppressed. Our results show how different physical parameters influence multiparameter estimation precision and provide a detailed discussion of the associated physical mechanisms in the steady state. Our results focus on exploring practical Gaussian measurement schemes that can be realized experimentally. Besides, we further analyze the system's dynamics, comparing both the SLD quantum Fisher information (QFI) and the classical Fisher information (CFI) for both homodyne and heterodyne detection. This approach provides a robust foundation for multiparameter quantum estimation, offering significant potential for application in hybrid magnomechanical and optomechanical systems.

quant-ph↗

arXiv2026

Digital-Analog quantum Rabi simulation in the Deep Strong Coupling Regime

We study the quantum Rabi model (QRM) in the deep strong coupling (DSC) regime. To capture the full dynamics of the QRM in the DSC regime, we implemented single-qubit rotations combined with integrated digital steps and qubit-bosonic blocks. This approach leads to a paradigm known as digital analog quantum simulations (DAQSs). In this work, we review the encoding of QRM in the DSC regime through emerging paradigms of digital and analog techniques. Using DAQSs encoding, an efficient simulation can be performed on state-of-the-art circuit quantum electrodynamics platforms. Finally, we provide detailed information on the dynamics of the QRM in varity of parameter regions. We demonstrate the effectiveness of the DAQS paradigms in achieving prolonged coherent measurements during time evolution, even in the case of perturbative DSC regime dynamics. This proposal lays the groundwork for simulating complex many-body dynamics that involve bosonic modes.

quant-ph↗

arXiv2025

Coherent feedback-enhanced asymmetry of thermal process in open quantum systems: Cavity optomechanics

Entropy production is a fundamental concept in nonequilibrium thermodynamics, providing a direct measure of the irreversibility inherent in any physical process. In this work, we investigate in steady-state the enhancement of irreversibility employing coherent feedback loop. We evaluate the steady-state entropy production rate and quantum correlations by applying the quantum phase space formulation to calculate the entropy change. Our study reveals the essential contribution of coherent feedback in the thermal bath's input-noise operators, resulting in the system being driven far from thermal equilibrium. Our analysis shows that in the small-coupling limit, the entropy production rate is proportional to the quantum mutual information. We use for application the optomechanical system of Fabry-Pérot cavity, and show that the picks of the entropy production corresponding of the heating/cooling of movable mirror are improved. Therefore, we conclude that irreversibility and quantum correlations are not independent and must be analyzed jointly. The results demonstrate the possibility of enhancement of entropy production and pave the way for promising quantum thermal applications through coherent feedback loop.

quant-ph↗

arXiv2025

Optimal Multiparameter Quantum Estimation of Magnonic Couplings in a Magnomechanical Cavity

In this work, we introduce an experimentally viable scheme to enhance the simultaneous estimation precision of the couplings $G_{mc}$ and $G_{mb}$, with a particular focus on the performance of heterodyne detection. By comparing simultaneous and individual estimation strategies, we demonstrate that the simultaneous approach offers a notable advantage in our system. To support this, we compute the quantum Fisher information matrices (QFIMs) based on the symmetric logarithmic derivative (SLD) and the right logarithmic derivative (RLD). Our results show that the quantum Cramér Rao bound (QCRB) associated with the RLD is consistently lower than that of the SLD, indicating superior estimation precision. From a physical standpoint, this improvement reflects the system's enhanced capacity to encode, transfer, and extract quantum information while allowing optimal control of fundamental interactions. We show that increasing the Rabi frequency, cavity loss rate, and the average number of photons and phonons, combined with reduced mechanical damping and temperature, enhances the system's sensitivity to the coupling parameters. These mechanisms act on the available quantum resources, such as entanglement, squeezing, and state purity, leading to more precise estimations. Furthermore, our analysis reveals that under certain conditions, heterodyne detection can closely approach the ultimate precision set by the QFIM. This suggests that a measurement strategy based on heterodyne detection can offer an efficient and practical route for estimating the couplings $G_{mc}$ and $G_{mb}$, paving the way for high precision hybrid quantum sensors.

quant-ph↗

arXiv2025

Minimal Weak Gravity Conjecture And Gauge Duality in M-theory on K3xT2

The minimal Weak Gravity Conjecture (WGC) predicts the emergence of towers of superextremal states in both weak and strong coupling limits. In this work, we study M-theory compactified on a special class of Calabi-Yau threefolds to construct a 5D effective field theory (EFT) that accommodates both weak and strong gauge coupling limits. Building on a classification of fiber structures of Calabi-Yau threefolds with finite volume, we establish a correspondence between curves in the fiber and the base, which relates weak and strong gauge couplings. This allows us to probe non-perturbative effects by treating strong couplings through their weakly counterparts. We use this result and properties of Bogomol'nyi-Prasad-Sommerfield (BPS) states to demonstrate that M-theory on such Calabi-Yau threefold exhibits towers of superextremal BPS states in the aforementioned extreme limits as expected by the minimal WGC.

hep-th↗

arXiv2025

Magnon-rotation enhanced nonreciprocity of multipartite entanglement in a magnomechanical system

Nonreciprocal physics is attracting significant interest in quantum information processing. In this work, we propose a scheme to investigate the nonreciprocity of bi- and tripartite entanglement and generate squeezed states in a magnomechanical system. This is achieved through the Barnett effect, which originates from the rotation of the first magnon mode. The system consists of two YIG spheres, each supporting a magnon mode that represents collective spin motion, positioned inside a microwave cavity (MC). We show that the Barnett effect enhances entanglement under thermal effects and generates squeezed states for the two magnon modes and the photon mode. Moreover, we show that magnon-magnon coupling enhances entanglement between different two modes.

quant-ph↗

arXiv2025

Monogamy of Gaussian quantum steering and entanglement in a hybrid qubit-cavity optomagnonic system with coherent feedback loop

The monogamy of quantum correlations is a fundamental principle in quantum information processing, limiting how quantum correlations can be shared among multiple subsystems. Here we propose a theoretical scheme to investigate the monogamy of quantum steering and genuine tripartite entanglement in a hybrid qubit-cavity optomagnonic system with a coherent feedback loop. Using logarithmic negativity and Gaussian quantum steering, we quantify entanglement and steerability, respectively. We verify the CKW-type monogamy inequalities which leads to steering monogamous through adjustments of the reflective parameter among three tripartite modes versus temperature. Our results show that a coherent feedback loop can enhance entanglement and quantum steering under thermal effects.

quant-ph↗

arXiv2025

Exploiting Non-Markovian Memory Effects for Robust Quantum Teleportation

The reliable transmission of quantum information remains a central challenge in the presence of environmental noise. In particular, maintaining high teleportation fidelity in open quantum systems is hindered by decoherence, which disrupts quantum coherence and entanglement. Traditional noise mitigation techniques often neglect the rich temporal correlations present in realistic environments. This raises a key question: can non-Markovian memory effects be harnessed to improve the performance of quantum teleportation? In this work, we address this problem by analyzing how non-Markovian dynamics influence teleportation fidelity. We employ a statistical speed approach based on the Hilbert Schmidt norm to witness information backflow and monitor the system's instantaneous evolution rate. Our study focuses on two measurement-based strategies: weak measurement (WM) combined with quantum measurement reversal (QMR), and a hybrid protocol integrating environment-assisted measurement (EAM) with post selection and QMR. Through analytical expressions and detailed numerical simulations, we demonstrate that both strategies can enhance teleportation fidelity under non-Markovian noise. Notably, the EAM-based scheme exhibits superior robustness, achieving high fidelity even without fine-tuned parameters. Our results establish a concrete link between non-Markovian memory effects, statistical speed, and coherence preservation, offering practical insights for the design of resilient quantum communication protocols.

quant-ph↗

arXiv2025

Hermitian vs non-Hermitian quantum thermometry

We investigate the dephasing dynamics of a qubit as an effective mechanism for estimating the temperature of its surrounding environment for different symmetrizes. Our approach is fundamentally quantum, leveraging the qubit's susceptibility to decoherence without necessitating thermal equilibrium with the system under study. We also examine how symmetry properties affect the accuracy of information retrieval and the robustness of quantum information storage in such systems, highlighting their potential advantages in mitigating decoherence effects. The optimization of quantum Fisher information is performed with respect to both the interaction duration and the environmental temperature, focusing on Ohmic-like spectral density environments. Furthermore, we explicitly identify the optimal qubit measurement that attains the quantum Cramer-Rao bound for precision. Our findings reveal that optimal estimation arises from a complex interplay between the qubit's dephasing dynamics and the Ohmic characteristics of the environment with a particular focus on non-Hermitian systems that exhibit enhanced resilience to decoherence. Notably, optimal estimation does not occur when the qubit reaches a stationary state nor under conditions of complete dephasing.

quant-ph↗