Graphene-based qubits in quantum communications

Abstract

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.Comment: 4 figure

Ferromagnetism in the unusual low-valence layered material LaSrNiRuO 4

“…We first did a constrained LSDA+U calculation, assuming the Ni + S = 1/2 but Ru 2+ S = 0 states with the doubly occupied 3z 2 − r 2 , xz and yz orbitals of the Ru 4d. In many cases, this type of calculations can find several orbitally polarized metastable solutions, in addition to the ground state [22][23][24]. Unfortunately, however, the present constrained LSDA+U calculation turns out not to stabilize the Ru 2+ S = 0 state, and it converges exactly to the Ni + S = 1/2 and Ru 2+ S = 1 FM insulating ground state.…”

Anomalous magnetic and spin glass behavior in Nb-substituted LaCo1−xNbxO3

“…Here, the double exchange interactions between Co 3+ and Co 4+ are playing an important role in controlling the magnetic/spin-state transitions. Also, the layered cobaltites La 2−x Sr x CoO 4 (containing both Co 2+ and Co 3+ ) are very interesting to understand the role of different spin as well as valence states of Co ions in controlling the magnetic, transport and electronic properties [35][36][37][38][39][40][41]. For example, it has been reported that the Co 2+ present mostly in HS state, whereas different spin-states are possible in Co 3+ [37,38].…”

Concentration and distribution of entanglement based on valley qubits system in graphene

“…Each QD can be described by the valley (denoted as s v ) degree of freedom and the spin (denoted as r) degree of freedom. Considering the excitation process of the electron in QD from valence band to the quantized conduction band, the effective interaction between the electrons of the QDs can be described as [12]:…”

“…As discussed in Ref. [12], the valley qubit is realized by utilizing two coupled QDs in gapped graphene. Quantum state transfer from a photon qubit to a valley qubit could be realized in the same system.…”