We propose an efficient scheme for transferring quantum states and generating entangled states between two qubits of different nature. The hybrid system consists a single nitrogen vacancy(NV) center and a superconducting (SC) qubit, which couple to an optical cavity and a microwave resonator, respectively. Meanwhile, the optical cavity and the microwave resonator are coupled via the electro-optic effect. By adjusting the relative parameters, we can achieve high fidelity quantum state transfer as well as highly entangled states between the NV center and the SC qubit. This protocol is within the reach of currently available techniques, and may provide interesting applications in quantum communication and computation with single NV centers and SC qubits.
We propose an efficient scheme for a coherent quantum interface between microwave and optical photons using nitrogen-vacancy (NV) centers in diamond. In this setup, an NV center ensembleis simultaneously coupled to an optical and a microwave cavity. We show that, by using the collective spin excitation modes as an intermediary, quantum states can be transferred between the microwave cavity and the optical cavity through either a double-swap scheme or a dark-state protocol. This hybrid quantum interface may provide interesting applications in single microwave photon detections or quantum information processing.
We present an experimental feasible scheme to synthesize two-mode
continuous-variable entangled states of two superconducting resonators that are
interconnected by two gap-tunable superconductingqubits. We show that, with
each artificial atom suitably driven by a bichromatic microwave field to induce
sidebands in the qubit-resonator coupling, the stationary state of the photon
fields in the two resonators can be cooled and steered into a two-mode squeezed
vacuum state via a dissipative quantum dynamical process, while the
superconducting qubits remain in their ground states. In this scheme the qubit
decay plays a positive role and can help drive the system to the target state,
which thus converts a detrimental source of noise into a resource.