Noise-induced distributed entanglement in atom-cavity-fiber system

Abstract

The distributed quantum computation plays an important role in large-scale quantum information processing. In the atom-cavity-fiber system, we put forward two efficient proposals to prepare the steady entanglement of two distant atoms with dissipation. The atomic spontaneous emission and the loss of fiber are exploited actively as powerful resources, while the effect of cavity decay is inhibited by quantum Zeno dynamics and quantumjump-based feedback control. These proposals do not require precisely tailored Rabi frequencies or coupling strength between cavity and fiber. Furthermore, we discuss the feasibility of extending the present schemes into the systems consisting of two atoms at the opposite ends of the n cavities connected by (n − 1) fibers, and the corresponding numerical simulation reveals that a high fidelity remains achievable with current experimental parameters. FIG. 1: (a) Diagrammatic illustration of the cavity-atom-fiber system and the atomic level for preparation of the Bell stateThe effective transitions of the reduced system.[51, 52], a more general process, the quantum Zeno dynamics was raised, where the system can evolve away from its initial state under a multidimensional projection [53][54][55][56]. The quantum Zeno dynamics provides us with the possibility to significantly restrain the cavity decay in QIP tasks [57][58][59][60][61][62][63][64][65]. On the other hand, the quantum feedback is usually applied in decoherence suppression, entanglement production, and entanglement protection [66][67][68][69][70][71][72][73][74]. This technology is based on immediately feeding back the measurement results to the quantum system of interest and then alter its subsequent dynamics. For instance, Mancini et al. controlled steady state Einstein-Podolsky-Rosen correlations for two bosonic modes interacting via parametric Hamiltonian by the quantum feedback [69]. Carvalho et al.proposed a direct feedback based on quantum-jump detection to achieve the maximal entangled states between two atoms in a cavity [70], and then they found that the quantum-jump-based feedback can protect highly entangled states against decoherence by comparing the effects of different control Hamiltonians and detection processes [71].In this paper, we propose two dissipative schemes to generate distant entangled Bell state and Knill-Laflamme-Milburn (KLM) state of two atoms with high fidelity, respectively, where two Λ atoms are trapped in two separated cavities connected by a fiber. We eliminate the unconcerned states by dispersive microwave fields, and inhibit the cavity decay by the quantum Zeno dynamics and the quantum-jump-based feedback control. The schemes have four distinctive features: (i) The target state is independent of the concrete initial states. (ii) The schemes are robust against the loss of photon, and the spontaneous emission of atoms and the decay of fibers are powerful resources to create target states. (iii) The atoms in different cavities are more convenient to be manipulated, and needn't precisely tailored...

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