Abstract
We investigate the creation of highly entangled ground states in a system of three exchange-coupled qubits arranged in a ring geometry. Suitable magnetic field configurations yielding approximate Greenberger-Horne-Zeilinger and exact ground states are identified. The entanglement in the system is studied at finite temperature in terms of the mixed-state tangle . By generalizing a conjugate gradient optimization algorithm originally developed to evaluate the entanglement of formation, we demonstrate that can be calculated efficiently and with high precision. We identify the parameter regime for which the equilibrium entanglement of the tripartite system reaches its maximum.
- Received 11 May 2007
DOI:https://doi.org/10.1103/PhysRevLett.100.100502
©2008 American Physical Society