Rongzhen Jiao

Universal quantum controlled phase gate on photonic qubits based on nitrogen vacancy centers and microcavity resonators.

Here we investigate a physical implementation of the universal quantum controlled phase (CPHASE) gate operation on photonic qubits by using nitrogen vacancy (N-V) centers and microcavity resonators. The quantum CPHASE gate can be achieved by sending the photons through the microcavity and interacting with the N-V center. The proposed scheme can be further used for scalable quantum computation. We show that this technique provides us a deterministic source of cluster state generation on photonic qubits. In this scheme, only single photons and single N-V center are required and the proposed schemes are feasible with the current experimental technology.

Concentration of entangled nitrogen-vacancy centers in decoherence free subspace

Exploiting the input-output process of low-Q cavities confining nitrogen-vacancy centers, we present an efficient entanglement concentration protocol on electron spin state in decoherence free subspace. Less entangled state can be concentrated to maximally entangled state with the assistance of single photon detection. With its robustness and scalability, the present protocol is immune to dephasing and can be further applied to quantum repeaters and distributed quantum computation.

Fano resonances based on multimode and degenerate mode interference in plasmonic resonator system

In this paper, three Fano resonances based on three different physical mechanisms are theoretically and numerically investigated in a plasmonic resonator system, comprised of two circular cavities. And the multimode interference coupled mode theory (MICMT) including coupling phases is proposed to explain the Fano resonances in plasmonic resonator system. According to MICMT, one of the Fano resonances originates from the interference between different resonant modes of one resonator, the other is induced by the interference between the resonant modes of different resonators. Mode degeneracy is removed when the symmetry of the system is broken, thereby emerging the third kind of Fano resonance which is called degenerate interference Fano resonance, and the degenerate interference coupled mode theory (DICMT) is proposed to explain this kind of Fano resonance. The sensitivity and FOM* (figure of merit) of these Fano resonances can be as high as 840 nm/RIU and 100, respectively. These are useful for fundamental study and applications in sensors, splitters and slow-light devices.

Amplification of Absorption Induced by Localized Surface Plasmons in Superconducting Nanowire Single-Photon Detector

The absorption can be amplified by using tungsten silicide (WSi) and metallic nano-antennas, which is related with the detection efficiency of a superconducting nanowire single-photon detector based on surface plasmons. A metal slot sandwiched between two hydrogen silsequioxane (HSQ), WSi nanowire, and metallic fan nano-antennas are the elements of the proposed single-photon detector. The slot is also filled with HSQ and WSi nanowire is inserted in the top of the slot. Metallic fan nano-antennas are added no WSi nanowire and the all these elements are deposed on the sapphire substrate. Our results show that the absorption/the detection efficiency of our proposed structure is much larger than the one with the niobium nitride (NbN) nanowire. There is an optimal width of WSi nanowire and the distance between WSi nanowire and metallic nano-antennas for the absorption/the detection efficiency of the detector. Our structure provides suitable parameters for designing SNSPD in experiments.