Title: Optimal local preparation of an arbitrary mixed state of two qubits: Closed expression for the single-copy case
Abstract: We consider the problem of preparing a single copy of an arbitrary two-qubit mixed state $\ensuremath{\rho},$ starting from an entangled pure state $\ensuremath{\psi}$ and using only local operations assisted with classical communication. We present an analytical expression for the minimal amount of pure-state entanglement required, and describe the corresponding local strategy. We also examine optimal probabilistic generalizations of the previous process.