document: Pairwise thermal entanglement in the n-qubit -LRB- n < or = 5 -RRB- Heisenberg XX chain We have calculated the concurrence of the pairwise thermal entanglement for the four-qubit and five-qubit Heisenberg XX chain . It is found that there is a great difference between the even-qubit and the odd-qubit chain in the aspect of the critical temperature and of the existence of the entanglement for the case of the qubit number n no more than 5
doc_bio_tags: B I I O O O O O O O O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O
extractive_keyphrases: pairwise thermal entanglement critical temperature
abstractive_keyphrases: four-qubit heisenberg xx chain five-qubit heisenberg xx chain even-qubit chain odd-qubit chain