arXiv subjects

Berihu Teklu

Publications and source records attributed to Berihu Teklu.

At least 19 recordsLinked to original sources

arXiv2026

Thermodynamic Performance of a Measurement-Driven Quantum Engine with a Two-Parameter $(p,q)$-Deformed Harmonic Oscillator

We address a measurement-driven, single-bath quantum engine that generates usable work using quantum measurement backaction. The working medium is a two-parameter $(p,q)$-deformed harmonic oscillator, whose nonlinear spectrum modifies the energy gaps sampled by a nonselective Gaussian measurement and the work exchanged during quasistatic adiabatic strokes. The cycle starts from a Gibbs state and consists of an adiabatic change of $(\omega,p,q)$, measurement of the final effective position quadrature, a reverse adiabatic stroke, and thermalization with the original bath. Using a consistent first-law convention, we derive the measurement heat, adiabatic work contributions, thermalization heat, and reduced working-medium efficiency. We also express the measurement stroke via a transition matrix and identify passivity/unitality conditions that ensure nonnegative measurement heat. Numerical scans show that, within the finite-basis, spectral-ordering, and engine-operation checks used in this work, deformation can enhance measurement-induced energy input and extracted work relative to the undeformed oscillator. The physical engine regime is selected by $\QM>0$, $\Wcyc<0$, $\QT<0$, and $0<\eta<1$. The reported efficiency is reduced and excludes measurement-apparatus costs.

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arXiv2026

Position- and Momentum-Space Quantum Information Measures of the Double-Morse Oscillator

We investigate the quantum-information properties of a particle confined by the double Morse potential in position and momentum spaces. The quasi-exact solvability of the model gives analytical expressions for the first two bound states, allowing the corresponding probability densities to be analyzed directly. Shannon entropy, Onicescu energy, Fisher information, statistical complexity, and Fisher-Shannon products are evaluated as functions of the parameter $A$, which controls the transition from a well-separated double well to a merged single-well profile. The position distribution is more delocalized and structurally complex when the double-well character is pronounced, whereas the momentum distribution exhibits the complementary trend. As the wells merge, the ground-state Fisher--Shannon product approaches its Gaussian reference value, whereas the excited state retains stronger non-Gaussian structure.

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arXiv2026

Exact Quasiprobability Hierarchy of the Double-Morse Oscillator: From Potential Geometry to Operator Ordering

Phase-space and quasiprobability methods now play operational roles in quantum technologies, characterizing localization, non-Gaussianity, nonclassical resources, and coarse-graining. We develop an exact, representation-consistent analysis of the lowest quasi-exact ground state of the symmetric double-Morse oscillator. In the double-Morse potential, the dimensionless parameter $A$ controls the separation of the minima and the central barrier, thereby changing the physical ground state. At fixed $A$, the Cahill--Glauber parameter $s$ labels the quasiprobability $W_A^{(s)}(q,p)$: $s=0$, $-1$, and $1$ give the Wigner, Husimi $Q$, and Glauber--Sudarshan $P$ representations, respectively. Although the potential is double-welled for $0<A<1$, the exact ground-state amplitude is single-peaked at the origin and lies above the barrier; as $A$ approaches unity, the merged well remains locally quartic rather than harmonic. Closed analytical expressions are obtained for the Wigner function and Weyl characteristic function. The Wigner function displays the $A$-dependent exchange between position and momentum localization and retains negative regions, certifying nonclassicality and, for this pure state, non-Gaussianity. The Weyl function is its Fourier dual, generates symmetrically ordered moments and cumulants, and yields the full $s$-ordered hierarchy. For $s<0$, isotropic Gaussian smoothing suppresses fine sign-changing structure while preserving the large-scale localization envelope. The Husimi endpoint is nonnegative without implying classicality, whereas the $P$ representation remains distributional. Thus, $A$ controls the physical phase-space geometry, while $s$ controls how the same non-Gaussian and nonclassical state is resolved across complementary representations.

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arXiv2026

Nonlinearity and Quantum Metrology in the Double-Morse Potential

We address the nonlinear properties of the double-Morse potential as a resource for single-mode quantum states due to its double-well structure and anharmonicity. We obtain analytical expressions for the ground-state wavefunction and the corresponding ground-state energy, using the asymmetry (width) parameter $α$ as the primary control parameter. We then assess non-Gaussianity and nonclassicality as quantitative signatures of nonlinearity and quantumness, and we find that both increase monotonically with $α$. Furthermore, we analyze the metrological performance of the model for estimating the structural parameter $α$. By evaluating the corresponding Fisher information, we show that position measurements are optimal and can saturate the Cramér-Rao bound. In particular, the estimation of $α$ is most precise in the shallow-well regime, where the quantum Fisher information is largest. For deep wells, enhanced sensitivity is instead obtained for the reparameterized control variable $A=2e^{-αx_0}$, provided that $x_0$ is independently calibrated. These results establish the double-Morse potential as a controllable source of non-Gaussianity and nonclassicality, with a metrological behavior that depends on the chosen estimation parameter. We highlight possible applications of this model in quantum sensing, continuous-variable quantum information, and quantum simulation.

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arXiv2026

Environment-assisted squeezing in a coherently driven non-Hermitian degenerate parametric oscillator

Environment-assisted approaches to nonclassical light offer a practical path to strong squeezing in imperfect, lossy platforms. In this paper, we study a degenerate parametric oscillator in which a coherently driven cavity is coupled to a broadband squeezed reservoir via a single-port mirror. At the same time, the intracavity dynamics include non-Hermitian (gain-loss-imbalanced) terms. Within input--output theory, we obtain closed-form expressions for the steady-state quadrature variances, the output squeezing spectrum, and the power spectrum, and map their dependence on the reservoir squeeze factor, the coherent drive amplitude, and the parametric gain. We find that the non-Hermitian contributions open operating windows in which the intracavity quadrature noise is markedly suppressed below the standard quantum limit and, depending on the parameter set, either sharpen or amplify spectral squeezing and power-spectral features at the output. The non-Hermitian coefficients are treated as effective, low-order drift parameters that describe calibrated imbalance between engineered source and sink channels after auxiliary degrees of freedom have been eliminated. The analysis is restricted to the stable Gaussian regime in which the drift matrix is stable, and the squeezed-reservoir diffusion matrix remains physical. The results demonstrate an environment-assisted approach in which reservoir engineering and coherent driving work together to enhance squeezing. The resulting parameter maps identify experimentally testable windows, rather than a unique device prescription, for combining reservoir squeezing, coherent driving, and controlled gain/loss imbalance in cavity-QED and nonlinear photonic settings.

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arXiv2026

Influence of quantum decoherence on the survival of quantumness in neutrino oscillations

This study examines the dynamics of quantumness in two-flavor neutrino oscillations subjected to a dephasing channel, using representative oscillation parameters associated with the KamLAND, MINOS, and Daya Bay experiments. We analyze three complementary quantum-correlation measures -- entanglement of formation (EOF), quantum discord (QD), and local quantum uncertainty (LQU) -- within an effective two-qubit description. In the unitary case, all three measures display oscillatory behavior controlled by flavor mixing, and their amplitudes are strongly shaped by the relevant mixing angle. MINOS exhibits the largest correlations because $θ_{23}$ is close to maximal, KamLAND shows intermediate values associated with the solar sector, and Daya Bay yields smaller correlations due to the relatively small value of $θ_{13}$. Under dephasing, the off-diagonal coherence terms are suppressed and the three quantifiers decrease accordingly, while QD remains non-zero in regimes where entanglement is weak. For pure states, LQU satisfies $\mathcal{U}=\mathcal{C}^2$ and therefore tracks entanglement monotonically, whereas QD provides a broader witness of non-classical correlations. These results provide a compact quantum-information description of two-flavor neutrino oscillations in both coherent and dephased regimes. We also quantify the sensitivity of these observables to oscillation and decoherence parameters, showing that their main added value relative to flavor probabilities is their direct response to off-diagonal coherence loss.

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arXiv2025

Stroboscopic Saturation of Multiparameter Quantum Limits in Distributed Quantum Sensing

High-precision sensors that exploit uniquely quantum phenomena have been shown to surpass the standard quantum limit of measurement precision. However, in the general scenario where multiple parameters are simultaneously encoded in a quantum probe, while surpassing the standard quantum limit is possible, its practical attainability is severely hindered. This difficulty arises due to the fundamental incompatibility among the optimal measurements required for estimating different parameters. A naturally multiparameter sensing scenario emerges when a network of quantum sensors is spatially distributed, with each individual sensor probing a distinct parameter of interest. The central goal in such a setting is twofold: first, to surpass the standard quantum limit in estimating global properties of the system -- thereby achieving quantum-enhanced sensitivity for a given network size -- and second, to explicitly identify the optimal measurement strategies necessary to practically attain this quantum advantage. Here, we analytically demonstrate quantum-enhanced sensitivity for a broad class of distributed quantum probes, including cases where the precision scales quadratically or quartically with the sensing resources. We construct the corresponding optimal measurement strategies that achieve the ultimate precision limits -- namely, saturation of both the Holevo and quantum Cramér-Rao bounds. We then apply our framework to two concrete scenarios: the simultaneous estimation of multiple gravitational accelerations (gravimetry) and coupling strengths across spatially separated locations. Feasibility analyses indicate that the proposed distributed quantum-enhanced sensing schemes are within reach of current experimental capabilities.

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arXiv2025

Amplifying Two-Mode Squeezing in Nanomechanical Resonators

Quantum squeezing plays a crucial role in enhancing the precision of quantum metrology and improving the efficiency of quantum information processing protocols. We thus propose a scheme to amplify two-mode squeezing in nanomechanical resonators, harnessing parametric amplification and two-tone laser controls. The red-detuned laser drives facilitate the cooling of the nanomechanical resonators down to their ground state and allow optimal quantum state transfer in the weak-coupling, resolved sideband regime. In particular, the competing blue-detuned lasers in the driving pairs induce displacement squeezing in mechanical resonators. Thus, the quantum state transfer of the squeezing in nanomechanical resonators and the intracavity correlated photons of the parametric amplifier significantly enhance the two-mode mechanical squeezing. Notably, increasing the coupling strength of the red detuned laser and the ratio of blue-to-red detuned laser dramatically amplifies the two-mode mechanical squeezing under realistic experiment parameters of a typical optomechanical system. Our findings reveal that the proposed cooperative mechanism effectively enhances the level of two-mode mechanical squeezing with a considerable improvement and demonstrates exceptional resilience to thermal noise.

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arXiv2025

Optimizing mechanical entanglement using squeezing and parametric amplification

We propose a scheme of an optomechanical system that optimizes entanglement in nanomechanical resonators through quantum state transfer of intracavity squeezing and squeezed reservoir field sources assisted by radiation pressure. The system is driven by red-detuned laser fields, which enable simultaneous cooling of the mechanical resonators and facilitate the quantum state transfer in a weak coupling and good cavity limit. Specifically, the mechanical entanglement is quantified using logarithmic negativity within the bipartite Gaussian states of the two mechanical modes. The results show that several key parameters, including the parametric phase and nonlinear gain of the non-degenerate optical parametric amplifier, the strength of the squeezing reservoir, optomechanical cooperativity, thermal excitation of phonons, and the temperature of mechanical baths, strongly influence the degree of mechanical entanglement. Hence, the findings indicate that careful tuning of the parameters can enable control over the enhancement of entanglement robustness, suggesting that this optomechanical scheme provides a viable pathway for applications in quantum sensing and information processing

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arXiv2025

Frequency estimation by frequency jumps

The frequency of a quantum harmonic oscillator cannot be determined through static measurement strategies on a prepared state, as the eigenstates of the system are independent of its frequency. Therefore, dynamic procedures must be employed, involving measurements taken after the system has evolved and encoded the frequency information. This paper explores the precision achievable in a protocol where a known detuning suddenly shifts the oscillator's frequency, which then reverts to its original value after a specific time interval. Our results demonstrate that the squeezing induced by this frequency jump can effectively enhance the encoding of frequency information, significantly improving the quantum signal-to-noise ratio (QSNR) compared to standard free evolution at the same resource (energy and time) cost. The QSNR exhibits minimal dependence on the actual frequency and increases with both the magnitude of the detuning and the overall duration of the protocol. Furthermore, incorporating multiple frequency jumps into the protocol could further enhance precision, particularly for lower frequency values.

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arXiv2024

Enhancement of Opto-Electro-Mechanical Entanglement through Three-Level Atoms

We address the dynamical bipartite entanglement in an opto-electro-mechanical system that involves a three-level atom. The system consists of a degenerate three-level atom, a mechanical resonator, an optical cavity, and a microwave cavity. By utilizing the linearization approximation and nonlinear quantum-Langevin equations, the dynamics of the system are analyzed, and the bipartite entanglement is evaluated using the logarithmic negativity. The research findings indicate that the entanglement between each subsystem increases with the atom injection rate, suggesting that a higher atom injection rate leads to enhanced information transmission between the subsystems. Additionally, it is observed that the correlation between subsystems increases with an increase in the coupling rate. Moreover, the study demonstrates that the correlation between each subsystem decreases as temperature rises. We also show that the degree of tripartite entanglement diminishes with increasing atomic decay rates. The results highlight the positive impact of three-level atoms on the bipartite entanglement in an opto-electro-mechanical system. Consequently, such electro-optomechanical systems can offer a framework for optomechanical information transfer.

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arXiv2024

Critical metrology of minimally accessible anisotropic spin chains

We address quantum metrology in critical spin chains with anisotropy and Dzyaloshinskii-Moriya (DM) interaction, and show how local and quasi-local measurements may be exploited to characterize global properties of the systems. In particular, we evaluate the classical (magnetization) and quantum Fisher information of the relevant parameters for the density matrix of a single spin and that of a pair of spins ranging from nearest to sixth-nearest neighbors, to the limiting case of very distant spins. Our results allow us to elucidate the role of the different parameters and to individuate the optimal working regimes for the precise characterization of the system, also clarifying the effects of correlations on the estimation precision.

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arXiv2024

Strong mechanical squeezing in a microcavity with double quantum wells

In a hybrid quantum system composed of two quantum wells placed inside a cavity with a moving end mirror pumped by bichromatic coherent light, we address the formation of squeezed states of a mechanical resonator. The exciton mode and mechanical resonator interact indirectly via microcavity fields. Under the conditions of the generated coupling, we predict squeezing of the mechanical-mode beyond the resolved side-band regime with existing experimental parameters. Finally, we show that the robustness of this squeezing against thermal fluctuations is important for practical applications of such systems.

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arXiv2023

Irreversibility in an optical parametric driven optomechanical system

We investigate the role of nonlinearity via optical parametric oscillator on the entropy production rate and quantum correlations in a hybrid optomechanical system. Specifically, we derive the modified entropy production rate of an optical parametric oscillator placed in the optomechanical cavity which is well described by the two-mode Gaussian state. We find a dramatic deviation in the irreversibility and quantum mutual information for small detuning. Our analysis shows that the system irreversibility can be reduced by choosing the appropriate phase of the self-induced nonlinearity. We further demonstrate that the nonlinearity effect persist for a reasonable range of cavity decay rate.

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arXiv2022

Joint quantum estimation of loss and nonlinearity in driven-dissipative Kerr resonators

We address multiparameter quantum estimation for coherently driven nonlinear Kerr resonators in the presence of loss. In particular, we consider the realistic situation in which the parameters of interest are the loss rate and the nonlinear coupling, whereas the amplitude of the coherent driving is known and externally tunable. Our results show that this driven-dissipative model is asymptotically classical, i.e. the Uhlmann curvature vanishes, and the two parameters may be jointly estimated without any additional noise of quantum origin. We also find that the ultimate bound to precision, as quantified by the quantum Fisher information (QFI), increases with the interaction time and the driving amplitude for both parameters. Finally, we investigate the performance of quadrature detection, and show that for both parameters the Fisher information oscillates in time, repeatedly approaching the corresponding QFI.

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arXiv2022

Enhancement of magnon-photon-phonon entanglement in a cavity magnomechanics with coherent feedback loop

We propose a scheme to improve magnon-photon-phonon entanglement in cavity magnomechanics using coherent feedback loop. In addition, we prove that the steady state and dynamical state of the system is a genuine tripartite entanglement state. We use the logarithmic negativity as the witness of quantum correlations to quantify the entanglement of all bipartite subsystem, and genuine tripartite entanglement via the nonzero minimum residual contangle, in steady and dynamical regime. We consider the feasible experiment parameters to realize the tripartite entanglement. We show that the entanglement can be significantly improved with coherent feedback using a suitable tuning of the reflective parameter of the beam splitter. The entanglement is robust against the thermal effects. Our proposal scheme to improve the entanglement can be of interest to applications in quantum information.

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arXiv2022

Noisy propagation of Gaussian states in optical media with finite bandwidth

We address propagation and entanglement of Gaussian states in optical media characterised by non-trivial spectral densities. In particular, we consider environments with a finite bandwidth and show that in the low temperature regime: i) secular terms in the master equation may be neglected; ii) attenuation (damping) is strongly suppressed; iii) the overall diffusion process may be described as a Gaussian noise channel with variance depending only on the bandwidth. We find several regimes where propagation is not much detrimental and entanglement may be protected form decoherence.

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arXiv2022

Continuous-variable entanglement dynamics in Lorentzian environment

We address the non-Markovian entanglement dynamics for bimodal continuous variable quantum systems interacting with two independent structured reservoirs. We derive an analytical expression for the entanglement of formation without performing the Markov and the secular approximations. We observe a variety of qualitative features such as entanglement sudden death, dynamical generation, and protection for two types of Lorentzian spectral densities, assuming the two modes initially excited in a twin-beam state. Our quantitative analysis shows that these cases with different reservoir spectrum, the environmental temperature and the initial amount of entanglement differ significantly in these qualitative features.

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