Entangled webs: Tight bound for symmetric sharing of entanglement

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Authors	KOASHI M. BŮŽEK Vladimír IMOTO N.
Year of publication	2000
Type	Article in Periodical
Magazine / Source	Physical Review A
MU Faculty or unit	Faculty of Informatics
Citation
Field	Theoretical physics
Keywords	STATE ENTANGLEMENT; BELL THEOREM; QUANTUM; CRYPTOGRAPHY
Description	Quantum entanglement cannot be unlimitedly shared among an arbitrary number of qubits. The degree of bipartite entanglement decreases as the number of entangled pairs in an N-qubit system increases. We analyze a system of N qubits in which an arbitrary pair of particles is entangled. We show that the maximum degree of entanglement (measured in the concurrence) between any pair of qubits is 2/N. This tight bound can be achieved when the qubits are prepared in a pure symmetric (with respect to permutations) state with just one qubit in the basis stare \0 > and the others in the basis state \1 >.
Related projects:	Informatics as the third methodology Non-sequential Models of Computing -- Quantum and Concurrent Distributed Models of Computing