High Resolution Image Download MS PowerPoint Slide Nanophotonic quantum devices can significantly boost light–matter interaction, which is important for applications such as quantum networks. Reaching a high interaction strength between an optical transition of a spin system and a single mode of light is an essential step that demands precise control over all degrees of freedom of the optical coupling. While current devices have reached a high accuracy of emitter positioning, the placement process remains overall statistically, reducing the device fabrication yield. Furthermore, not all degrees of freedom of the optical coupling can be controlled, limiting the device performance. Here, we develop a hybrid approach based on negatively charged silicon vacancy center in nanodiamonds coupled to a mode of a Si 3 N 4 -photonic crystal cavity, where all terms of the coupling strength can be controlled individually. We used the frequency of coherent Rabi oscillations and line-broadening as a measure of the device performance. This allows for iterative optimization of the position and rotation of the dipole with respect to individual preselected modes of light. Therefore, our work marks an important step for optimization of hybrid quantum photonics and enables us to align device simulations with real device performance.
High Resolution Image Download MS PowerPoint Slide Nanophotonic quantum devices can significantly boost light–matter interaction, which is important for applications such as quantum networks. Reaching a high interaction strength between an optical transition of a spin system and a single mode of light is an essential step that demands precise control over all degrees of freedom of the optical coupling. While current devices have reached a high accuracy of emitter positioning, the placement process remains overall statistically, reducing the device fabrication yield. Furthermore, not all degrees of freedom of the optical coupling can be controlled, limiting the device performance. Here, we develop a hybrid approach based on negatively charged silicon vacancy center in nanodiamonds coupled to a mode of a Si 3 N 4 -photonic crystal cavity, where all terms of the coupling strength can be controlled individually. We used the frequency of coherent Rabi oscillations and line-broadening as a measure of the device performance. This allows for iterative optimization of the position and rotation of the dipole with respect to individual preselected modes of light. Therefore, our work marks an important step for optimization of hybrid quantum photonics and enables us to align device simulations with real device performance.
Nanophotonic quantum devices can significantly boost light-matter interaction which is important for applications such as quantum networks. Reaching a high interaction strength between an optical transition of a spin system and a single mode of light is an essential step which demands precise control over all degrees of freedom of the optical coupling. While current devices have reached a high accuracy of emitter positioning, the placement process remains overall statistically, reducing the device fabrication yield. Furthermore, not all degrees of freedom of the optical coupling can be controlled limiting the device performance. Here, we develop a hybrid approach based on negatively-charged silicon-vacancy center in nanodiamonds coupled to a mode of a Si3N4-photonic crystal cavity, where all terms of the coupling strength can be controlled individually. We use the frequency of coherent Rabi-oscillations and line-broadening as a measure of the device performance. This allows for iterative optimization of the position and the rotation of the dipole with respect to individual, preselected modes of light. Therefore, our work marks an important step for optimization of hybrid quantum photonics and enables to align device simulations with real device performance.
High Resolution Image Download MS PowerPoint Slide Spin-based, quantum-photonics promise to realize distributed quantum computing and quantum networks. The performance depends on an efficient entanglement distribution where cavity quantum electrodynamics could boost the efficiency. The central challenge is the development of compact devices with large spin-photon coupling rates and a high operation bandwidth. Photonic crystal cavities comprise strong field confinement but require highly accurate positioning of atomic systems in mode field maxima. Negatively charged silicon-vacancy centers in diamond emerged as promising atom-like systems. Spectral stability and access to long-lived, nuclear-spin memories enabled elementary demonstrations of quantum network nodes, including memory-enhanced quantum communication. In a hybrid approach, we deterministically place SiV-containing nanodiamonds inside one hole of one-dimensional, freestanding, Si 3 N 4 -based photonic crystal cavities and coherently couple individual optical transitions to cavity modes. We optimize light–matter coupling utilizing two-mode composition, waveguiding, Purcell-enhancement, and cavity-resonance tuning. The resulting photon flux increases by 14 compared to free space. Corresponding lifetime-shortening below 460 ps puts potential operation bandwidth beyond GHz rates.
Hybrid quantum photonic systems connect classical photonics to the quantum world and promise to deliver efficient light-matter quantum interfaces while leveraging the advantages of both, the classical and the quantum, subsystems. However, combining efficient, scalable photonics and solid-state quantum systems with desirable optical and spin properties remains a formidable challenge. In particular, the access to individual spin states and coherent mapping to photons remains unsolved for hybrid systems. In this paper, we demonstrate all-optical initialization and readout of the electron spin of a negatively charged silicon-vacancy center in a nanodiamond coupled to a silicon nitride photonic crystal cavity. We characterize relevant parameters of the coupled emitter-cavity system and determine the silicon-vacancy center’s spin-relaxation and spin-decoherence rate. Our results mark a key step towards the realization of a hybrid spin-photon interface based on silicon nitride photonics and the silicon-vacancy center’s electron spin in nanodiamonds with potential use for quantum networks, quantum communication, and distributed quantum computation. Published by the American Physical Society 2024
Efficient interfaces between optical photons and quantum bits are fundamental building blocks for quantum networks and large-scale quantum computers. We demonstrate an integrated platform for scalable quantum optics based on color centers coupled to diamond nanodevices. First, we incorporate nitrogen-vacancy (NV) centers in diamond into hybrid nanophotonic crystal cavities. Despite our progress towards coupling the NV to cavity photons, we find that the NV-cavity interface is limited by the imperfections of the color center's properties and its local environment. We approach this challenge first by characterizing and modifying the diamond surface to reduce the environmental noise affecting the NV optical transition. Subsequently, we develop a new approach that makes use of a quantum emitter with intrinsic protection from this noise: the silicon-vacancy (SiV) center in diamond. We demonstrate that SiV centers introduced through ion implantation feature highly coherent optical transitions, even inside nanostructures. By placing SiV centers inside all-diamond photonic crystal cavities, we achieve strong SiV-photon coupling with a cooperativity of greater than 20. Using this platform, we realize a quantum-optical switch controlled by the spin degree of freedom of a single SiV. By measuring intensity correlations of indistinguishable Raman photons emitted into a single waveguide, we observe a quantum interference effect resulting from the superradiant emission of two probabilistically entangled SiV centers. Finally, we demonstrate controllable photon-mediated interactions between the spin degrees of freedom of two cavity-coupled SiV centers. When the optical transitions of the two SiV centers are tuned into resonance, the coupling of each SiV to the common cavity mode results in a coherent interaction between the two SiVs, leading to the observation of super- and sub-radiant two-SiV states.
Integrated nanophotonics is an emerging field with high potential for quantum technology applications such as quantum sensing or quantum networks. A desired photonics platform is Si 3 N 4 due to low-photon loss and well-established fabrication techniques. However, quantum optics applications are not yet established. Here, we investigate an approach toward Si 3 N 4 -based quantum photonics utilizing a crossed waveguide, pump–probe design. The platform enables efficient, on-chip excitation, strong background suppression, and at the same time, efficient coupling to the mode of a high- Q photonic crystal cavity. The freestanding photonic crystal cavities reach high Q -factors up to 47 × 10 3 . To test our platform, we positioned an ensemble of negatively charged nitrogen vacancy centers located in a nanodiamond within the interaction zone of the photonic crystal cavity. We quantify the efficiency of the coupling with the β λ -factor reaching values as large as 0.71. We further demonstrate on-chip excitation of the quantum emitter with strong suppression (∼20 dB) of the background fluorescence. Our results unfold the potential to utilize negatively charged nitrogen vacancy centers in nanodiamonds and Si 3 N 4 platforms as an efficient, on-chip spin-photon interface in quantum photonics experiments.
Summary form only given. Deterministic coupling of a single emitter to a photonic crystal cavity is an important step towards the realization of integrated solid-state devices for quantum photonics. As single emitters, color centers in diamond, e.g. the Nitrogen-Vacancy (NV) center or the Silicon-Vacancy (SiV) center have attracted significant interest due to their extraordinary properties like long spin-coherence times or narrowband and bright single photon emission, respectively. For the realization of recent proposals like cavity-enhanced spin measurements or cavity-enhanced single photon sources, it is necessary to couple single color centers to a cavity with small mode volume and high quality factor. Photonic crystal cavities directly fabricated within a monocrystalline diamond membrane are well suited for this task, as they offer tiny mode volumes for efficient emitter-cavity coupling as well as scalable architectures for integrated photonic devices.In order to achieve controlled coupling of a color center to a photonic crystal cavity, several challenges have to be tackled, e.g. exact emitter positioning and alignment of its dipole moment with the cavity electric field as well as the ability for cavity tuning. For deterministic emitter-cavity positioning, two different routes can be pursued: In the first approach, a single emitter is localized within the diamond, its dipole orientation is determined and the cavity is subsequently structured around it. In the second approach, the cavity is fabricated first and a single color center is created within the cavity, e.g. via ion implantion or creation of vacancies. Here we present strategies to realize both methods for deterministic emitter-cavity coupling. For the first approach, we use a monocrystalline diamond film containing single SiV centers. Figure 1a) shows a fluorescence scan of a single SiV center with position markers next to it. The position markers are subsequently used to structure a photonic crystal cavity around the color center using focused ion beam milling [1]. Figures 1b) and c) show SEMimages before and after the cavity fabrication. The photonic crystal lattice constant a ≈ 283nm is chosen such that the cavity modes are red shifted with respect to the SiV emission lines. Using an oxidation tuning method, the cavity modes are tuned into resonance with the zero-phonon line at 740nm of a single SiV center (see Fig. 1d)). On resonance, we measure an intensity enhancement by a factor of 3.8 compared to the off-resonant case.