arXiv subjects

Hideyo Tsurusawa

Publications and source records attributed to Hideyo Tsurusawa.

4 recordsLinked to original sources

arXiv2024

Space-division multiplexed phase compensation for quantum communication: concept and field demonstration

Phase-sensitive quantum communication has received considerable attention to overcome the distance limitation of quantum communication. A fundamental problem in phase-sensitive quantum communication is to compensate for phase drift in an optical fiber channel. A combination of time-, wavelength-, and space-division multiplexing can improve the phase stability of the optical fiber. However, the existing phase compensations have used only time- and wavelength-division multiplexing. Here, we demonstrate space-division multiplexed phase compensation in the Osaka metropolitan networks. Our compensation scheme uses two neighboring fibers, one for quantum communication and the other for sensing and compensating the phase drift. Our field investigations confirm the correlation of the phase drift patterns between the two neighboring fibers. Thanks to the correlation, our space-division multiplexed phase compensation significantly reduces the phase drift and improves the quantum bit error rate. Our phase compensation is scalable to a large number of fibers and can be implemented with simple instruments. Our study on space-multiplex phase compensation will support the field deployment of phase-sensitive quantum communication.

quant-ph↗

arXiv2021

Robotic fabrication of high-quality lamellae for aberration-corrected transmission electron microscopy

Aberration-corrected scanning transmission electron microscopy (STEM) is widely used for atomic-level imaging of materials. To accelerate the discovery of new materials based on atomic-level investigations, the throughput of aberration-corrected STEM experiments becomes more and more important. However, the throughput of the full workflow of aberration-corrected STEM is still quite low. A fundamental problem is that the preparation of high-quality thin STEM samples (lamellae) depends on manual operation. Here, inspired by the recent successes of "robot scientists", we demonstrate robotic fabrication of high-quality lamellae by focused-ion-beam (FIB) with full automation software. First, we show that robotic FIB can prepare lamellae with a high success rate, where the robotic FIB controls rough-milling, lift-out, and final-thinning processes. Then, we optimize the FIB parameters of the final-thinning process for single crystal Si. Aberration-corrected STEM imaging of these Si lamellae shows atomic-level images with 55 pm resolution. We also demonstrate robotic fabrication of high-quality lamellae of SrTiO3 and sapphire. The robotic FIB system will resolve the current bottleneck of the full workflow of aberration-corrected STEM analysis and accelerate materials discovery based on atomic-level imaging.

cond-mat.mtrl-sci↗

arXiv2018

Gelation as condensation frustrated by hydrodynamics and mechanical isostaticity

Colloidal gels have unique mechanical and transport properties that stem from their bicontinous nature, in which a colloidal network is intertwined with a viscous solvent, and have found numerous applications in foods, cosmetics, construction materials, and for medical applications, such as cartilage replacements. So far, our understanding of the process of colloidal gelation is limited to long-time dynamical effects, where gelation is viewed as a phase separation process interrupted by the glass transition. However, this picture neglects two important effects: the influence of hydrodynamic interactions, and the emergence of mechanical stability. With confocal microscopy experiments, here we successfully follow the entire process of gelation with a single-particle resolution, yielding time-resolved measures of internal stress and viscoelasticity from the very beginning of the aggregation process. First, we demonstrate that the incompressible nature of a liquid component constrains the initial stage of phase separation, assisting the formation of a percolated network. Then we show that this network is not mechanically stable and undergoes rearrangements driven by self-generated internal stress. Finally, we show that mechanical metastability is reached only after percolation of locally isostatic environments, proving isostaticity a necessary condition for the stability and load bearing ability of gels rather than the glass transition. Our work reveals the crucial roles of momentum conservation in gelation in addition to the conventional purely out-of-equilibrium thermodynamic picture.

cond-mat.soft↗

arXiv2018

Formation of porous crystals via viscoelastic phase separation

Viscoelastic phase separation of colloidal suspensions can be interrupted to form gels either by glass transition or by crystallization. With a new confocal microscopy protocol, we follow the entire kinetics of phase separation, from homogeneous phase to different arrested states. For the first time in experiments, our results unveil a novel crystallization pathway to sponge-like porous crystal structures. In the early stages, we show that nucleation requires a structural reorganization of the liquid phase, called stress-driven ageing. Once nucleation starts, we observe that crystallization follows three different routes: direct crystallization of the liquid phase, Bergeron process, and Ostwald ripening. Nucleation starts inside the reorganised network, but crystals grow past it by direct condensation of the gas phase on their surface, driving liquid evaporation, and producing a network structure different from the original phase separation pattern. We argue that similar crystal-gel states can be formed in monoatomic and molecular systems if the liquid phase is slow enough to induce viscoelastic phase separation, but fast enough to prevent immediate vitrification. This provides a novel pathway to form nano-porous crystals of metals and semiconductors without dealloying, which may be important for catalytic, optical, sensing, and filtration applications.

cond-mat.soft↗