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arXiv · 1810.11995

Two-qubit mixed states and teleportation fidelity: Purity, concurrence, and beyond

Sumit Nandi·Chandan Datta·Arpan Das·Pankaj Agrawal
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Abstract

To explore the properties of a two-qubit mixed state, we consider quantum teleportation. The fidelity of a teleported state depends on the resource state purity and entanglement, as characterized by concurrence. Concurrence and purity are functions of state parameters. However, it turns out that a state with larger purity and concurrence, may have comparatively smaller fidelity. By computing teleportation fidelity, concurrence and purity for two-qubit X-states, we show it explicitly. We further show that fidelity changes monotonically with respect to functions of parameters - other than concurrence and purity. A state with smaller concurrence and purity, but larger value of one of these functions has larger fidelity. These functions, thus characterize nonlocal classical and/or quantum properties of the state that are not captured by purity and concurrence alone. In particular, concurrence is not enough to characterize the entanglement properties of a two-qubit mixed state.

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Sumit Nandi, Chandan Datta, Arpan Das, Pankaj Agrawal. 2018-10-29. Two-qubit mixed states and teleportation fidelity: Purity, concurrence, and beyond. https://doi.org/10.1140/epjd%2Fe2018-90252-2

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