Rare-earth (RE) atoms in solid-state materials are attractive components for photonic quantum information systems because of their coherence properties even in high-temperature environments. We have experimentally performed the single-site optical spectroscopy and optical addressing of a single RE atom in an amorphous silica optical fiber at room temperature. The single-site optical spectroscopy of the tapered RE-doped fiber shows nonresonant emission lines similar to those seen in the case of an unstructured fiber and the autocorrelation function of photons emitted from the fiber shows the antibunching effect due to the spatial isolation given by the tapered fiber structure. The ability to address single RE atoms at room temperature provides a very stable and cost-effective technical platform for the realization of a solid-state system for a large-scale quantum optical network and other quantum technologies based on a large number of spectral channels from visible to midinfrared wavelengths.
Rare-earth (RE) atoms in solid-state materials are attractive components for photonic quantum information systems because of their coherence properties even in high-temperature environments. We have experimentally performed the single-site optical spectroscopy and optical addressing of a single RE atom in an amorphous silica optical fiber at room temperature. The single-site optical spectroscopy of the tapered RE-doped fiber shows nonresonant emission lines similar to those seen in the case of an unstructured fiber and the autocorrelation function of photons emitted from the fiber shows the antibunching effect due to the spatial isolation given by the tapered fiber structure. The ability to address single RE atoms at room temperature provides a very stable and cost-effective technical platform for the realization of a solid-state system for a large-scale quantum optical network and other quantum technologies based on a large number of spectral channels from visible to midinfrared wavelengths.
The fiber-coupled single-photon source, which can operate at room temperature, is an essential component for implementing optical quantum communication technologies such as quantum internet and quantum key distribution. Here, we experimentally demonstrated the generation of single photons at room temperature from a single Rare-Earth (RE) ion isolated in the optical tapered fiber. Our single photon source is fabricated based on commercially available RE ion doped fibers, which can be prepared at low cost. To investigate the characteristics of our single-photon source, several optical properties were also observed such as saturation intensity of the single RE ion. Our results will lead to the realization of various photonic quantum information technologies such as optical quantum communication networks.
In this thesis, we study the single-photon source using a rare-earth (RE) ion doped in a tapered fiber.Single-photon sources are key components for various optical quantum information technologies, and the development of low-cost single-photon sources has been desired for their implementation.A wide variety of emitters for single-photon sources have been studied.Among these emitters, RE ions have attracted much attention as single-photon emitters due to their high stability of luminescence and the sharpness of the emission spectrum with 4f transitions.In our single-photon source, we obtain spatially isolated single RE ions, which are separated from each other beyond the diffraction limit by tapering a commercially available RE-ion-doped silica fiber.RE ions doped in the silica fiber can be optically activated at room temperature.Therefore, our single-photon source does not need cryogenic systems.In addition, the emission wavelength can be selected based on the type of RE ions doped in the fiber.These features of our single-photon source enable the development of a low-cost and wavelength-selectable source.We performed the autocorrelation measurements using a neodymium (Nd 3+ ) ion in the tapered fiber, and showed the generation of single photons from the ion.In addition, we proposed a method to selectively excite a single RE ion in the tapered fiber, which can directly generate single photons within the tapered fiber, and collect them through the tapered fiber with high collection and channeling efficiencies.Generating single photons with this excitation method is proved by the autocorrelation measurements.We also observed the optical properties of the single photon emitted from the single Nd 3+ ion in the tapered fiber, such as the fluorescence lifetime, saturation intensity and polarization states.The fluorescence lifetime is one of the most important parameters for a single-photon source because this parameter is closely related to the emission rate.We observed the fluorescence lifetime of the single Nd 3+ ion in the tapered silica fiber and an 1 ensemble of the Nd 3+ ion in the unstructured silica fiber.The saturation power of the excitation laser and the saturated fluorescence intensity tell us the appropriate excitation power for generating single photons with high signal-to-noise ratio.Here, we measured the relationship between the fluorescence intensity from the single Nd 3+ ion and the power of the excitation light.In addition, the polarization state of the single photons emitted from the single Nd 3+ ion in the tapered fiber was observed.Our results will lead to the implementation of the low-cost and wavelength-selectable single-photon source to realize various optical quantum information technologies.
The realization of single-photon generation is important for implementing various quantum information technologies. The use of rare-earth ions in an optical fiber is a promising single-photon generation method due to its ability to operate at room temperature as well as the low cost involved. Neodymium ions are especially interesting because the ions are one of the most commercially affordable rare-earth materials in the current industry. The neodymium ion also has the advantage of having a rich energy level structure, which offers several possible wavelengths for emitted single photons from visible to near-telecommunication wavelengths. In this paper, we experimentally demonstrated single-photon generation using an isolated single neodymium ion in tapered silica fiber at room temperature. Our results have significant implications as a platform for low-cost wavelength-selectable single-photon sources and photonic quantum applications.
A fiber-coupled single-photon source is an essential component for the implementation of optical quantum communication technologies. Using the rare-earth ion doped in an optical fiber as an emitter is a significant method to construct such a photon source at room temperature, as well as achieving high coupling and channeling efficiency. In this study, we experimentally demonstrated the generation of single photons at room temperature by selectively exciting a sole rare-earth ion isolated within a tapered silica fiber. The key advantages of our method are the ability to manipulate a purely single ion and the efficient collection of photons from the guided mode of the fiber, owing to the single ion's emission of photons directly within the fiber. These features make our system a promising building block for realizing all-fiber-integrated optical quantum networks. We have also measured the optical lifetime of a single neodymium ion in the tapered fiber, and the result supports that the single-photon correlation time is practically determined by the absorption time of the ion.
High Resolution Image Download MS PowerPoint Slide Crystals and fibers doped with rare-earth (RE) ions provide the basis for most of today’s solid-state optical systems, from lasers and telecom devices to emerging potential quantum applications such as quantum memories and optical to microwave conversion. The two platforms, doped crystals and doped fibers, seem mutually exclusive, each having its own strengths and limitations, the former providing high homogeneity and coherence and the latter offering the advantages of robust optical waveguides. Here we present a hybrid platform that does not rely on doping but rather on coating the waveguide─a tapered silica optical fiber─with a monolayer of complexes, each containing a single RE ion. The complexes offer an identical, tailored environment to each ion, thus minimizing inhomogeneity and allowing tuning of their properties to the desired application. Specifically, we use highly luminescent Yb 3+ [Zn(II) MC (QXA)] complexes, which isolate the RE ion from the environment and suppress nonradiative decay channels. We demonstrate that the beneficial optical transitions of the Yb 3+ are retained after deposition on the tapered fiber and observe an excited-state lifetime of over 0.9 ms, on par with state-of-the-art Yb-doped inorganic crystals.
High-performance optical quantum memories serving as quantum nodes are crucial for the distribution of remote entanglement and the construction of large-scale quantum networks. Notably, quantum systems based on single emitters can achieve deterministic spin-photon entanglement, greatly simplifying the difficulty of constructing quantum network nodes. Among them, optically interfaced spins embedded in solid-state systems, as atomic-like emitters, are important candidate systems for implementing long-lived quantum memory due to their stable physical properties and robustness to decoherence in scalable and compact hardware. To enhance the light-matter-interaction strength, optical microcavities can be exploited as an important tool to generate high-quality spin-photon entanglement for scalable quantum networks. They can enhance the photon collection probability and photon generation rate of specific optical transitions and improve the coherence and spectral purity of emitted photons. For solid-state systems, open Fabry-Pérot cavities can couple single emitters that are not in proximity to the surface, avoiding significant spectral diffusion induced by the interfaces while maintaining the wide tunability, which enables addressing of multiple single emitters in the frequency and spatial domain within a single device. This review describes the characteristics of single emitters as quantum memories with a comparison to atomic ensembles, the cavity-enhancement effect for single emitters and the advantages of different cavities, especially fiber Fabry-Pérot microcavities. Finally, recent experimental progress on solid-state single emitters coupled with fiber Fabry-Pérot microcavities is reviewed, with a focus on color centers in diamond and silicon carbide, as well as rare-earth dopants.