Creation of Two-Particle Entanglement in Open Macroscopic Quantum Systems

Abstract EN

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 two-qubit 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.