Creation of Two-Particle Entanglement in Open Macroscopic Quantum Systems

Merkli, Marco and Berman, G. P. and Borgonovi, F. and Tsifrinovich, V. I. (2012) Creation of Two-Particle Entanglement in Open Macroscopic Quantum Systems. Advances in Mathematical Physics, 2012. ISSN 1687-9139

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Abstract

We consider an open quantum system of N not directly interacting spins (qubits) in contact with both local and collective thermal environments. The qubit-environment interactions are energy conserving. We trace out the variables of the thermal environments and N − 2 qubits to obtain the time-dependent reduced density matrix for two arbitrary qubits. We numerically simulate the reduced dynamics and the creation of entanglement (concurrence) as a function of the parameters of the thermal environments and the number of qubits, N. Our results demonstrate that the twoqubit entanglement generally decreases as N increases. We show analytically that, in the limit N → ∞, no entanglement can be created. This indicates that collective thermal environments cannot create two-qubit entanglement when many qubits are located within a region of the size of the environment coherence length. We discuss possible relevance of our consideration to recent quantum information devices and biosystems

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