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