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The European Physical Journal Special Topics

Multi-partite entanglement in Davies environment

Konrad Jałowiecki, Jerzy Dajka

Published Feb 20, 2019• 1 citation
Publisher

Abstract

We analyse dynamics of genuinely multi-partite entanglement of N-qubit states initially prepared in the form of so called X-matrices with one qubit coupled to a Davies-type environment. We develop an analytic formula for genuinely multi-partite concurrence of the investigated states as a function of time and analyze its time evolution with an emphasis on the qualitative difference between systems affected by a pure decoherence only and those which do dissipate energy at finite temperature.

DOI
10.1140/epjst/e2019-800042-9

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We study the entanglement dynamics of multi-qubit systems coupled to a common dissipative environment, focusing on systems with one or two initially excited qubits. Using the Lindblad master equation, we derive the time evolution of the density matrix and analyze the entanglement between qubit pairs via the concurrence measure. The solution method involves applying the Lindblad super-operator to the initial density matrix, generating a subspace of non-duplicate states. We extend our analysis to nnn-qubit systems, including three-qubit and four-qubit configurations, and explore the effects of thermal noise on entanglement dynamics. Our results demonstrate how initial conditions, system size, and environmental interactions shape entanglement, providing valuable insights for quantum information processing applications.
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We consider a many-body system consisting of a harmonic oscillator linearly coupled to NNN others and solve the corresponding dynamical problem analytically. Initially, the main oscillator is prepared in a superposition of two coherent states and the NNN others in the ground states. We divide this system in arbitrary three partitions and the entanglement dynamics between any of these partitions is quantified. We show that the residual entanglement of the tripartite system is always present. Besides, the concurrence of any two partitions depends on the overlap between the two coherent states forming the initial superposition of the main oscillator and the distribution of excitations in the partitions. Finally, we obtain a hierarchy of entanglement between the central oscillator and partitions formed by the other oscillators. For long times the excitations of the main oscillator are completely transferred to the NNN others and these are found entangled.
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We study the time evolution of two two-state systems (two qubits) initially in the pure entangled states or the maximally entangled mixed states interacting with the individual environmental noise. It is shown that due to environment noise, all quantum entangled states are very fragile and become a classical mixed state in a short-time limit. But the environment can affect entanglement in very different ways. The type of decoherence process for certain entangled states belongs to amplitude damping, while the others belong to dephasing decoherence.