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

  • Sumit NandiEmail author
  • Chandan Datta
  • Arpan Das
  • Pankaj Agrawal
Regular Article


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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Quantum Information 


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© EDP Sciences, SIF, Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Institute of Physics, Sachivalaya MargBhubaneswarIndia
  2. 2.Homi Bhabha National Institute, Training School ComplexAnushakti Nagar, MumbaiIndia

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