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Entanglement of a Pair of Quantum Bits

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arxiv quant-ph/9703041 v2 pith:SZFOTHWA submitted 1997-03-22 quant-ph

Entanglement of a Pair of Quantum Bits

classification quant-ph
keywords entanglementquantumformationformulamixedstatestatessystem
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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The ``entanglement of formation'' of a mixed state of a bipartite quantum system can be defined in terms of the number of pure singlets needed to create the state with no further transfer of quantum information. We find an exact formula for the entanglement of formation for all mixed states of two qubits having no more than two non-zero eigenvalues, and we report evidence suggesting that the formula is valid for all states of this system.

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