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Graphene-based qubits in quantum communications

We explore the potential application of graphene-based qubits in photonic quantum communications. In particular, the valley pair qubit in double quantum dots of gapped graphene is investigated as a quantum memory in the implementation of quantum repeaters. For the application envisioned here, our work extends the recent study of the qubit (Wu et al., arXiv: 1104.0443; Phys. Rev. B 84, 195463 (2011)) to the case where the qubit is placed in a normal magnetic field-free configuration. It develops, for the configuration, a method of qubit manipulation, based on a unique AC electric field-induced, valley-orbit interaction-derived mechanism in gapped graphene. It also studies the optical response of graphene quantum dots in the configuration, in terms of valley excitation with respect to photonic polarization, and illustrates faithful photon \leftrightarrow valley quantum state transfers. This work suggests the interesting prospect of an all-graphene approach for the solid state components of a quantum network, e.g., quantum computers and quantum memories in communications.