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Entangled webs: Tight bound for symmetric sharing of entanglement

Masato Koashi·Vladimir Buzek·Nobuyuki Imoto
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Abstract

Quantum entanglement cannot be unlimitedly shared among arbitrary number of qubits. Larger the number of entangled pairs in an N-qubit system, smaller the degree of bi-partite entanglement is. 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 state |0> and the others in the basis state |1>.

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Masato Koashi, Vladimir Buzek, Nobuyuki Imoto. 2000-07-24. Entangled webs: Tight bound for symmetric sharing of entanglement. https://doi.org/10.1103/physreva.62.050302

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