Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

The Journal of V N Karazin Kharkiv National University Series Physics

INFLUENCE OF DECOHERENCE PARAMETERS ON THE EFFICIENCY OF PRESERVING ENTANGLEMENT OF TWO-QUBIT WERNER STATES THROUGH QUANTUM MEASUREMENTS

O. M. Konovalenko, Z. А. Maizelis

Published May 28, 2025• 0 citations
Publisher

Abstract

In this work we analyse how a protocol of joint, periodically repeated measurements influences the preservation of state coherence and thereby maintains entanglement in two-qubit systems prepared in a Werner state. By modeling the linear interactions of each qubit with independent dissipative environments (with coefficients , ) together with the dispersive interactions (with coefficients ), we introduce the algorithmic “efficiency” parameter , which quantitatively characterises how strongly these measurements slow down the loss of coherence and support the underlying quantum correlations.. For the maximally entangled input state (Werner state parameter ), the efficiency shows a hyperbolic dependence on the dispersive‐coupling parameter in the strong linear-coupling regime, when , In the opposite regime, when , efficiency asymptotically approaches unity, indicating a loss of capability to suppress decoherence in environments dominated by dispersive interactions. A comprehensive numerical study has been performed on the entanglement-preservation efficiency across all three relevant parameters—namely, the linear and dispersive couplings of each qubit to the environment and the Werner-state parameter that quantifies the initial entanglement. The algorithm’s performance is analyzed in various limiting cases, including the minimal and maximal values of the Werner parameter examined in this work, as well as scenarios in which the linear-interaction strength approaches the dispersive one. The results obtained indicate that carefully tailored measurement schemes, combined with a high level of quantum-system entanglement, can effectively neutralize the deleterious influence of the environment. This paves the way for formulating detailed, quantitatively substantiated recommendations for tuning dynamic coherence-protection procedures that enhance the reliability of entanglement preservation across a variety of quantum algorithms, including entanglement-based quantum-cryptography protocols (BB84, E91/BBM92, DI-QKD, as well as multi-correlation quantum secret-sharing schemes such as HBB99) and variational algorithms for materials simulation (VQE, ADAPT-VQE, QITE, VQSD and related UCC-based approaches).

DOI
10.26565/2222-5617-2025-42-02

Related papers

Entanglement Degradation in Two Interacting Qubits Coupled to Dephasing Environments

Rahma Abdelmagid, Khadija Alshehhi, Gehad Sadiek

One of the main obstacles toward building efficient quantum computing systems is decoherence, where the inevitable interaction between the qubits and the surrounding environment leads to a vanishing entanglement. We consider a system of two interacting asymmetric two-level atoms (qubits) in the presence of pure and correlated dephasing environments. We study the dynamics of entanglement while varying the interaction strength between the two qubits, their relative frequencies, and their coupling strength to the environment starting from different initial states of practical interest. The impact of the asymmetry of the two qubits, reflected in their different frequencies and coupling strengths to the environment, varies significantly depending on the initial state of the system and its degree of anisotropy. For an initial disentangled, or a Werner, state, as the difference between the frequencies increases, the entanglement decay rate increases, with more persistence at the higher degrees of anisotropy in the former state. However, for an initial anti-correlated Bell state, the entanglement decays more rapidly in the symmetric case compared with the asymmetric one. The difference in the coupling strengths of the two qubits to the pure (uncorrelated) dephasing environment leads to higher entanglement decay in the different initial state cases, though the rate varies depending on the degree of anisotropy and the initial state. Interestingly, the correlated dephasing environment, within a certain range, was found to enhance the entanglement dynamics starting from certain initial states, such as the disentangled, anti-correlated Bell, and Werner, whereas it exhibits a decaying effect in other cases such as the initial correlated Bell state.

Entropy•Oct 17, 2023•5 citations

Unique entanglement time evolution of two-qubit product separable and extended Werner-like states in a discrete qubit environment

Renzo P. Alporha, Lemuel John F. Sese, Rayda Gammag

Abstract This study investigates the parameters affecting the entanglement time evolution of product separable (PS) and extended Werner-like (EWL) states in homogeneous, white noise, and mixed environments. In a pure homogeneous environment, both states demonstrate complete entanglement revivals, where an increase in the number of environments leads to an attenuation of concurrence. The PS state exhibits gaps and never reaches a maximum entanglement, whereas maximum purity EWL states (Bell states) maintain or periodically reach maximum entanglement. Hence, the PS and EWL states have a disjoint entanglement time evolution subspaces. Interestingly, the environment interaction and subsystem coupling interaction that influence entanglement have an inverse time relationship under a constant value of concurrence. Placing the system of interest in a white noise environment induces entanglement dissipation, with the dissipation time dependent on the width of random distribution of interaction strengths rather than the magnitude of interaction strength. In a distinct qubit environment, the entanglement time evolution of the PS state depends on the distribution of the number of environments. Moreover, combining homogeneous and white noise environments results in entanglement dynamics that exhibit characteristics of both homogeneous and white noise.

arXiv:2409.16244•Physica Scripta•Jul 10, 2025•0 citations

Entanglement properties of superconducting qubits coupled to a semi-infinite transmission line

Yang-Qing Guo, Ping‐Xing Chen, Jian Li

Quantum entanglement, a key resource in quantum information processing, is reduced by interaction between the quantum system concerned and its unavoidable noisy environment. Therefore it is of particular importance to study the dynamical properties of entanglement in open quantum systems. In this work, we mainly focus on two qubits coupled to an adjustable environment, namely a semi-infinite transmission line. The two qubits’ relaxations, through individual channels or collective channel or both, can be adjusted by the qubits’ transition frequencies. We examine entanglement dynamics in this model system with initial Werner state, and show that the phenomena of entanglement sudden death and revival can be observed. Due to the hardness of preparing the Werner state experimentally, we introduce a new type of entangled state called pseudo-Werner state, which preserves as much entangling property as the Werner state, and more importantly, it is experiment friendly. Furthermore, we provide detailed procedures for generating pseudo-Werner state and studying entanglement dynamics with it, which can be straightforwardly implemented in a superconducting waveguide quantum electrodynamics system.

arXiv:2204.08219•Chinese Physics B•Mar 3, 2023•1 citation

Long-time preservation of correlations through the interactions among cavities as engineered environments

K. Berrada, Hichem Eleuch

Abstract In this present manuscript, we explore the possibility to preserve and manipulate of classical and quantum correlations initially present in a system of qubits, where each qubit is immersed in a cavity that is interacted with another cavity as an engineered environment. We consider the qubit entropy, entanglement of formation, quantum discord, and classical correlation for Markovian and non-Markovian regimes. We find that the correlations can be maintained and enhanced during the dynamics, which is a useful dynamical feature, by adjusting the strength coupling constant between cavities for weak- and strong- coupling regime (W- and S-CR). In particular, we have found that, for the case of perfect cavities, high values of correlations can be achieved during the evolution with respect to the strength coupling between cavities. The obtained results can provide more hints for future studies on the control of correlations with optimal conditions. By a specific selection of the model parameters, long-time preservation of correlations can be achieved without being affected by the decoherence.

Quantum Information Processing•Jul 10, 2025•0 citations

Quantum Zeno and anti-Zeno effects on the entanglement dynamics of qubits dissipating into a common and non-Markovian environment

Alireza Nourmandipour, Mohammad Kazem Tavassoly, M. A. Bolorizadeh

We investigate the quantum Zeno and anti-Zeno effects on pairwise entanglement dynamics of a collective of noninteracting qubits which have been initially prepared in a Werner state and are off-resonantly coupled to a common and non-Markovian environment. We obtain the analytical expression of the concurrence in the absence and presence of the nonselective measurements. In particular, we express our results in the strong and weak coupling regimes and examine the role of the system size and the effect of the detuning from the cavity field frequency on the temporal behavior of the pairwise entanglement. We show that the detuning parameter has a positive role in protection of entanglement in the absence of the measurement for the weak coupling regime. We find that for the values of detuning parameter less than the cavity damping rate, the quantum Zeno effect is always dominant, while for values greater than the cavity damping rate, both Zeno and anti-Zeno effects can occur, depending on the measurement intervals. We also find that the anti-Zeno effect can occur in the pairwise entanglement dynamics in the absence and presence of the detuning in the strong coupling regime.

arXiv:1607.01160•Journal of the Optical Society of America B•Jul 15, 2016•33 citations

Decoherence of two maximally entangled qubits in a lossy nonlinear cavity

Adam Miranowicz

Decoherence effect on quantum entanglement of two optical qubits in a lossy cavity interacting with a nonlinear medium (Kerr nonlinearity) is analysed. The qubits are assumed to be initially in the maximally entangled states (Bell or Bell-like states) or the maximally entangled mixed states, on the example of Werner and Werner-like states. Two kinds of measures of the entanglement are considered: the concurrence to describe a decay of the entanglement of formation of the qubits, and the negativity to determine a decay of the entanglement cost under positive-partial-transpose-preserving operations. It is observed that the Kerr nonlinearity, in the discussed decoherence model, does not affect the entanglement of the qubits initially in the Bell or Werner states, although the evolution of the qubits can depend on this nonlinearity explicitly. However, it is shown that for the initial Bell-like state and the corresponding Werner-like state, the loss of the entanglement can be periodically reduced by inserting the Kerr nonlinearity in the lossy cavity. Moreover, the relativity of the entanglement measures is demonstrated, to our knowledge for the first time, as a result of a physical process.

arXiv:quant-ph/0402025•Journal of Physics A Mathematical and General•Jul 28, 2004•20 citations
In this work we analyse how a protocol of joint, periodically repeated measurements influences the preservation of state coherence and thereby maintains entanglement in two-qubit systems prepared in a Werner state. By modeling the linear interactions of each qubit with independent dissipative environments (with coefficients , ) together with the dispersive interactions (with coefficients ), we introduce the algorithmic “efficiency” parameter , which quantitatively characterises how strongly these measurements slow down the loss of coherence and support the underlying quantum correlations.. For the maximally entangled input state (Werner state parameter ), the efficiency shows a hyperbolic dependence on the dispersive‐coupling parameter in the strong linear-coupling regime, when , In the opposite regime, when , efficiency asymptotically approaches unity, indicating a loss of capability to suppress decoherence in environments dominated by dispersive interactions. A comprehensive numerical study has been performed on the entanglement-preservation efficiency across all three relevant parameters—namely, the linear and dispersive couplings of each qubit to the environment and the Werner-state parameter that quantifies the initial entanglement. The algorithm’s performance is analyzed in various limiting cases, including the minimal and maximal values of the Werner parameter examined in this work, as well as scenarios in which the linear-interaction strength approaches the dispersive one. The results obtained indicate that carefully tailored measurement schemes, combined with a high level of quantum-system entanglement, can effectively neutralize the deleterious influence of the environment. This paves the way for formulating detailed, quantitatively substantiated recommendations for tuning dynamic coherence-protection procedures that enhance the reliability of entanglement preservation across a variety of quantum algorithms, including entanglement-based quantum-cryptography protocols (BB84, E91/BBM92, DI-QKD, as well as multi-correlation quantum secret-sharing schemes such as HBB99) and variational algorithms for materials simulation (VQE, ADAPT-VQE, QITE, VQSD and related UCC-based approaches).
One of the main obstacles toward building efficient quantum computing systems is decoherence, where the inevitable interaction between the qubits and the surrounding environment leads to a vanishing entanglement. We consider a system of two interacting asymmetric two-level atoms (qubits) in the presence of pure and correlated dephasing environments. We study the dynamics of entanglement while varying the interaction strength between the two qubits, their relative frequencies, and their coupling strength to the environment starting from different initial states of practical interest. The impact of the asymmetry of the two qubits, reflected in their different frequencies and coupling strengths to the environment, varies significantly depending on the initial state of the system and its degree of anisotropy. For an initial disentangled, or a Werner, state, as the difference between the frequencies increases, the entanglement decay rate increases, with more persistence at the higher degrees of anisotropy in the former state. However, for an initial anti-correlated Bell state, the entanglement decays more rapidly in the symmetric case compared with the asymmetric one. The difference in the coupling strengths of the two qubits to the pure (uncorrelated) dephasing environment leads to higher entanglement decay in the different initial state cases, though the rate varies depending on the degree of anisotropy and the initial state. Interestingly, the correlated dephasing environment, within a certain range, was found to enhance the entanglement dynamics starting from certain initial states, such as the disentangled, anti-correlated Bell, and Werner, whereas it exhibits a decaying effect in other cases such as the initial correlated Bell state.
Abstract This study investigates the parameters affecting the entanglement time evolution of product separable (PS) and extended Werner-like (EWL) states in homogeneous, white noise, and mixed environments. In a pure homogeneous environment, both states demonstrate complete entanglement revivals, where an increase in the number of environments leads to an attenuation of concurrence. The PS state exhibits gaps and never reaches a maximum entanglement, whereas maximum purity EWL states (Bell states) maintain or periodically reach maximum entanglement. Hence, the PS and EWL states have a disjoint entanglement time evolution subspaces. Interestingly, the environment interaction and subsystem coupling interaction that influence entanglement have an inverse time relationship under a constant value of concurrence. Placing the system of interest in a white noise environment induces entanglement dissipation, with the dissipation time dependent on the width of random distribution of interaction strengths rather than the magnitude of interaction strength. In a distinct qubit environment, the entanglement time evolution of the PS state depends on the distribution of the number of environments. Moreover, combining homogeneous and white noise environments results in entanglement dynamics that exhibit characteristics of both homogeneous and white noise.
Quantum entanglement, a key resource in quantum information processing, is reduced by interaction between the quantum system concerned and its unavoidable noisy environment. Therefore it is of particular importance to study the dynamical properties of entanglement in open quantum systems. In this work, we mainly focus on two qubits coupled to an adjustable environment, namely a semi-infinite transmission line. The two qubits’ relaxations, through individual channels or collective channel or both, can be adjusted by the qubits’ transition frequencies. We examine entanglement dynamics in this model system with initial Werner state, and show that the phenomena of entanglement sudden death and revival can be observed. Due to the hardness of preparing the Werner state experimentally, we introduce a new type of entangled state called pseudo-Werner state, which preserves as much entangling property as the Werner state, and more importantly, it is experiment friendly. Furthermore, we provide detailed procedures for generating pseudo-Werner state and studying entanglement dynamics with it, which can be straightforwardly implemented in a superconducting waveguide quantum electrodynamics system.
Abstract In this present manuscript, we explore the possibility to preserve and manipulate of classical and quantum correlations initially present in a system of qubits, where each qubit is immersed in a cavity that is interacted with another cavity as an engineered environment. We consider the qubit entropy, entanglement of formation, quantum discord, and classical correlation for Markovian and non-Markovian regimes. We find that the correlations can be maintained and enhanced during the dynamics, which is a useful dynamical feature, by adjusting the strength coupling constant between cavities for weak- and strong- coupling regime (W- and S-CR). In particular, we have found that, for the case of perfect cavities, high values of correlations can be achieved during the evolution with respect to the strength coupling between cavities. The obtained results can provide more hints for future studies on the control of correlations with optimal conditions. By a specific selection of the model parameters, long-time preservation of correlations can be achieved without being affected by the decoherence.
We investigate the quantum Zeno and anti-Zeno effects on pairwise entanglement dynamics of a collective of noninteracting qubits which have been initially prepared in a Werner state and are off-resonantly coupled to a common and non-Markovian environment. We obtain the analytical expression of the concurrence in the absence and presence of the nonselective measurements. In particular, we express our results in the strong and weak coupling regimes and examine the role of the system size and the effect of the detuning from the cavity field frequency on the temporal behavior of the pairwise entanglement. We show that the detuning parameter has a positive role in protection of entanglement in the absence of the measurement for the weak coupling regime. We find that for the values of detuning parameter less than the cavity damping rate, the quantum Zeno effect is always dominant, while for values greater than the cavity damping rate, both Zeno and anti-Zeno effects can occur, depending on the measurement intervals. We also find that the anti-Zeno effect can occur in the pairwise entanglement dynamics in the absence and presence of the detuning in the strong coupling regime.
Decoherence effect on quantum entanglement of two optical qubits in a lossy cavity interacting with a nonlinear medium (Kerr nonlinearity) is analysed. The qubits are assumed to be initially in the maximally entangled states (Bell or Bell-like states) or the maximally entangled mixed states, on the example of Werner and Werner-like states. Two kinds of measures of the entanglement are considered: the concurrence to describe a decay of the entanglement of formation of the qubits, and the negativity to determine a decay of the entanglement cost under positive-partial-transpose-preserving operations. It is observed that the Kerr nonlinearity, in the discussed decoherence model, does not affect the entanglement of the qubits initially in the Bell or Werner states, although the evolution of the qubits can depend on this nonlinearity explicitly. However, it is shown that for the initial Bell-like state and the corresponding Werner-like state, the loss of the entanglement can be periodically reduced by inserting the Kerr nonlinearity in the lossy cavity. Moreover, the relativity of the entanglement measures is demonstrated, to our knowledge for the first time, as a result of a physical process.