arXiv subjects

Alto Osada

Publications and source records attributed to Alto Osada.

14 recordsLinked to original sources

arXiv2025

Integrated Multi-Wavelength Photonic Architectures for Future Scalable Trapped Ion Quantum Devices

Recent advances of quantum technologies rely on precise control and integration of quantum objects, and technological breakthrough is anticipated for further scaling up to realize practical applications. Trapped-ion quantum technology is a promising candidates to realize them, while its scalability depends on the development of intra-node scaling up, reproducibility of quantum nodes and photonic interconnection among them. Utilization of integrated photonics instead of free-space optics is a crucial step toward mass production of trapped-ion quantum nodes and manifests itself as useful for laser delivery for various quantum operations and photon detection. However, whole architecture of the scalable photonic circuits for them is left unexplored. In this work, we discuss photonic architectures for trapped-ion quantum devices, in which lasers of multiple wavelengths are delivered to multiple trapping zones within a single chip. We analyze two methods of configuring nanophotonic waveguides and compare them in terms of loss of total laser power. This work opens up a new landscape of photonic architecture for various applications not only to quantum ones such as trapped-ion devices but also to classical photonics, e.g. optoelectronic devices and biochemical sensing.

quant-ph↗

arXiv2025

Optical vortex generation by magnons with spin-orbit-coupled light

Light possesses both spin and orbital angular momentum. In spatially asymmetric optical fields, these properties undergo spontaneous coupling, referred to as optical spin-orbit coupling. The study of the coupling has recently become central in modern optics due to its substantial applications in communications, sensing, and quantum control. A key challenge is to clarify the relationship between the origins of spatially asymmetric optical fields and the resulting spin-orbit coupling. Current research focuses on materials and configurations exhibiting spatial asymmetry, such as focusing lenses, interfaces, inhomogeneous media, and metasurfaces. However, Maxwell's equations indicate that matter can introduce both spatial and temporal asymmetry into optical fields. For instance, magnetic ordering breaks the time-reversal symmetry of interacting optical fields via the magneto-optic effect, introducing nonreciprocity in the resulting optical phenomena. Despite the importance, optical phenomena involving both spatially and temporally asymmetric optical fields remain unexplored. Here, we demonstrate that breaking time and spatial symmetries through magnons and light focusing, respectively, transforms an input Gaussian beam into a specific optical vortex beam in a nonreciprocal manner. This phenomenon is quantitatively explained by integrating the physics of magnon-induced Brillouin light scattering with optical spin-orbit coupling. The observed conservation of total angular momentum, encompassing both magnons and photons, further indicates that magnons can control both spin and orbital angular momentum of light. Finally, we outline future research directions enabled by asymmetric optical fields in both space and time.

physics.optics↗

arXiv2025

A Troubleshooting Framework for Trapping Ions

Practical knowledge about troubleshooting and error handling in trapped-ion systems remains largely undocumented and held within individual labs, creating a barrier to cross-disciplinary collaboration towards engineering scalable systems. This paper presents a structured troubleshooting framework for trapping ions, developed through hands-on experience in the lab. The framework categorizes standard failure modes across subsystems -- vacuum, electronics, optics, and imaging -- and organizes them into a modular decision-tree structure. Each troubleshooting action is annotated with estimates of cost and operational risk inspired by the principles of Failure Mode and Effects Analysis (FMEA). By categorizing failure modes and their associated costs, this work bridges the gap between physicists and engineers, enabling collaborative system design and setting the stage for turning experimental setups into robust, reproducible products. This framework provides a structured basis for future error-handled ion-trap systems, designed with diagnostics and maintainability in mind -- for use in distributed quantum computing and networks.

quant-ph↗

arXiv2023

Compact atom source using fiber-based pulsed laser ablation

We designed, demonstrated, and characterized an atom source based on fiber-based pulsed laser ablation. By using commercially available miniature lens system for focusing nanosecond pulsed laser of up to 225~$\mu$J delivered through a multimode fiber of 105~$\mu$m core, we successfully ablate a SrTiO$_3$ target and generate a jet of neutral strontium atoms, though our method can be applied to other transparent ablation targets containing materials under concern. Our device endures 6\,000 cycles of pulse delivery and irradiation without noticeable damage on the fiber facets and lenses. The generated strontium beam is characterized with spectroscopic method and is revealed to exhibit the transverse temperature of 800~K and longitudinal velocity of 2\,300~m/s, which are typical of pulsed-laser-ablation-based atom source. The number of atoms generated by a single ablation pulse is estimated to be $2\times 10^5$. Our device provides a compact, cryo-compatible fiber-pigtailed atom source with minimized device footprints and reduced complexity of vacuum systems to further promote the developments of cold-atom experiments. It may also find interesting applications in atomic and molecular sciences.

physics.atom-ph↗

arXiv2023

All-microwave manipulation of superconducting qubits with a fixed-frequency transmon coupler

All-microwave control of fixed-frequency superconducting quantum computing circuits is advantageous for minimizing the noise channels and wiring costs. Here we introduce a swap interaction between two data transmons assisted by the third-order nonlinearity of a coupler transmon under a microwave drive. We model the interaction analytically and numerically and use it to implement an all-microwave controlled-Z gate. The gate based on the coupler-assisted swap transition maintains high drive efficiency and small residual interaction over a wide range of detuning between the data transmons.

quant-ph↗

arXiv2023

Efficient low-energy single-electron detection using a large-area superconducting microstrip

Superconducting strip single-photon detectors (SSPDs) are excellent tools not only for single-photon detection but also for single-particle detection owing to their high detection efficiency, low dark counts, and low time jitter. Although the detection of various particles, including electrons with keV-scale energy, has been reported so far, there have been no studies for detecting low-energy electrons. It has yet to be clarified how low-energy electrons interact with electrons and/or phonons in a superconductor during electron detection. Here we report the detection property of a superconducting micro-strip single-electron detector (SSED) for electrons with energy below 200 eV. The detection efficiency is estimated as at least 37 % when electrons impinging on the stripline possess an energy of 200 eV. We also show that the minimum detectable energy of electrons is about 10 eV with our SSED, much lower than those of ions, which implies that the electron-electron interaction plays a significant role. SSEDs might open a wide range of applications, from condensed matter physics to quantum information science, because of their compatibility with the cryogenic environment.

quant-ph↗

arXiv2022

Feasibility study on ground-state cooling and single-phonon readout of trapped electrons using hybrid quantum systems

Qubits of long coherence time and fast quantum operations are long-sought objectives towards the realization of high-fidelity quantum operations and their applications to the quantum technologies. An electron levitated in a vacuum by a Paul trap is expected to be a good candidate, for its light mass and hence the high secular frequency which allows for the faster gate operations than those in trapped ions. Controlling the motional state of the trapped electron is a crucial issue, for it mediates an interaction between electron spins, intrinsic qubits embedded in electrons, and its decoherence results in degraded fidelity of two-qubit gates. In addition, an efficient readout of the motional state is important, regarding the possibility of detecting spin state by using it. Despite of such an importance, how to achieve the motional ground state and how to efficiently detect it are not reported so far. Here we propose methods addressing these issues by utilizing hybrid quantum systems involving electron-superconducting circuit and electron-ion coupled systems and analyze the feasibility of our schemes. In both systems, we show that the ground-state cooling and the single-phonon readout of the motional state of the trapped electron are possible. Our work shed light on the way to precisely control the motional states of the trapped electrons, that provides an interesting playground for the development of quantum technologies.

quant-ph↗

arXiv2021

Deterministic loading of a single strontium ion into a surface electrode trap using pulsed laser ablation

Trapped-ion quantum technologies have been developed for decades toward applications such as precision measurement, quantum communication and quantum computation. Coherent manipulation of ions' oscillatory motions in an ion trap is important for quantum information processing by ions, however, unwanted decoherence caused by fluctuating electric-field environment often hinders stable and high-fidelity operations.. One way to avoid this is to adopt pulsed laser ablation for ion loading, a loading method with significantly reduced pollution and heat production. Despite the usefulness of the ablation loading such as the compatibility with cryogenic environment, randomness of the number of loaded ions is still problematic in realistic applications where definite number of ions are preferably loaded with high probability. In this paper, we demonstrate an efficient loading of a single strontium ion into a surface electrode trap generated by laser ablation and successive photoionization. The probability of single-ion loading into a surface electrode trap is measured to be 82\,\%, and such a deterministic single-ion loading allows for loading ions into the trap one-by-one. Our results open up a way to develop more functional ion-trap quantum devices by the clean, stable, and deterministic ion loading.

quant-ph↗

arXiv2020

Fast parametric two-qubit gates with suppressed residual interaction using a parity-violated superconducting qubit

We demonstrate fast two-qubit gates using a parity-violated superconducting qubit consisting of a capacitively-shunted asymmetric Josephson-junction loop under a finite magnetic flux bias. The second-order nonlinearity manifesting in the qubit enables the interaction with a neighboring single-junction transmon qubit via first-order inter-qubit sideband transitions with Rabi frequencies up to 30~MHz. Simultaneously, the unwanted static longitudinal~(ZZ) interaction is eliminated with ac Stark shifts induced by a continuous microwave drive near-resonant to the sideband transitions. The average fidelities of the two-qubit gates are evaluated with randomized benchmarking as 0.967, 0.951, 0.956 for CZ, iSWAP and SWAP gates, respectively.

quant-ph↗

arXiv2019

In-situ wavelength tuning of quantum-dot single-photon sources integrated on a CMOS silicon chip

Silicon quantum photonics provides a promising pathway to realize large-scale quantum photonic integrated circuits (QPICs) by exploiting the power of complementary-metal-oxide-semiconductor (CMOS) technology. Toward scalable operation of such silicon-based QPICs, a straightforward approach is to integrate deterministic single-photon sources (SPSs). To this end, hybrid integration of deterministic solid-state SPSs, such as those based on InAs/GaAs quantum dots (QDs), is highly promising. However, the spectral and spatial randomness inherent in the QDs pose a serious challenge for scalable implementation of multiple identical SPSs on a silicon CMOS chip. To overcome this challenge, we have been investigating a new hybrid integration technique called transfer printing, which is based on a pick-and-place operation and allows for the integration of desired QD SPSs on any locations on the silicon CMOS chips at will. Nevertheless, even in this scenario, in-situ fine tuning for perfect wavelength matching among the integrated QD SPSs will be required for interfering photons from the dissimilar sources. Here, we demonstrate in-situ wavelength tuning of QD SPSs integrated on a CMOS silicon chip. To thermally tune the emission wavelengths of the integrated QDs, we augmented the QD SPSs with optically driven heating pads. The integration of all the necessary elements was performed using transfer printing, which largely simplified the fabrication of the three-dimensional stack of micro/nanophotonic structures. We further demonstrate in-situ wavelength matching between two dissimilar QD sources integrated on the same silicon chip. Our transfer-printing-based approach will open the possibility for realizing large-scale QPICs that leverage CMOS technology.

physics.app-ph↗

arXiv2019

GaAs valley photonic crystal waveguide with light-emitting InAs quantum dots

We report a valley photonic crystal (VPhC) waveguide in a GaAs slab with InAs quantum dots (QDs) as an internal light source exploited for experimental characterization of the waveguide. A topological interface state formed at the interface between two topologically-distinct VPhCs is used as the waveguide mode. We demonstrate robust propagation for near-infrared light emitted from the QDs even under the presence of sharp bends as a consequence of the topological protection of the guided mode. Our work will be of importance for developing robust photonic integrated circuits with small footprints, as well as for exploring active semiconductor topological photonics.

physics.optics↗

arXiv2018

Quantum-dot single-photon source on a CMOS silicon photonic chip integrated using transfer printing

Silicon photonics is a powerful platform for implementing large-scale photonic integrated circuits (PICs), because of its compatibility with mature complementary-metal-oxide-semiconductor (CMOS) technology. Exploiting silicon-based PICs for quantum photonic information processing (or the so-called silicon quantum photonics) provides a promising pathway for large-scale quantum applications. For the development of scalable silicon quantum PICs, a major challenge is integrating on-silicon quantum light sources that deterministically emit single photons. In this regard, the use of epitaxial InAs/GaAs quantum dots (QDs) is a very promising approach, because of their capability of deterministic single-photon emission with high purity and indistinguishability. However, the required hybrid integration is inherently difficult and often lacks the compatibility with CMOS processes. Here, we demonstrate a QD single-photon source (SPS) integrated on a glass-clad silicon photonic waveguide processed by a CMOS foundry. Hybrid integration is performed using transfer printing, which enables us to integrate heterogeneous optical components in a simple pick-and-place manner and thus assemble them after the entire CMOS process is completed. We observe single-photon emission from the integrated QD and its efficient coupling into the silicon waveguide. Our transfer-printing-based approach is fully compatible with CMOS back-end processes, and thus will open the possibility for realizing large-scale quantum PICs that leverage CMOS technology.

physics.app-ph↗

arXiv2018

Strongly coupled single quantum dot-cavity system integrated on a CMOS-processed silicon photonic chip

Quantum photonic integrated circuit (QPIC) is a promising tool for constructing integrated devices for quantum technology applications. In the optical regime, silicon photonics empowered by complementary-metal-oxide-semiconductor (CMOS) technology provides optical components useful for realizing large-scale QPICs. Optical nonlinearity at the single-photon level is required for QPIC to facilitate photon-photon interaction. However, to date, realization of optical elements with deterministic( i.e., not probabilistic) single-photon nonlinearity by using silicon-based components is challenging, despite the enhancement of the functionality of QPICs based on silicon photonics. In this study, we realize for the first time a strongly coupled InAs/GaAs quantum dot-cavity quantum electrodynamics (QED) system on a CMOS-processed silicon photonic chip. The heterogeneous integration of the GaAs cavity on the silicon chip is performed by transfer printing. The cavity QED system on the CMOS photonic chip realized in this work is a promising candidate for on-chip single-photon nonlinear element, which constitutes the fundamental component for future applications based on QPIC, such as, coherent manipulation and nondestructive measurement of qubit states via a cavity, and efficient single-photon filter and router.

cond-mat.mes-hall↗

arXiv2016

Bidirectional conversion between microwave and light via ferromagnetic magnons

Coherent conversion of microwave and optical photons in the single-quantum level can significantly expand our ability to process signals in various fields. Efficient up-conversion of a feeble signal in the microwave domain to the optical domain will lead to quantum-noise-limited microwave amplifiers. Coherent exchange between optical photons and microwave photons will also be a stepping stone to realize long-distance quantum communication. Here we demonstrate bidirectional and coherent conversion between microwave and light using collective spin excitations in a ferromagnet. The converter consists of two harmonic oscillator modes, a microwave cavity mode and a magnetostatic mode called Kittel mode, where microwave photons and magnons in the respective modes are strongly coupled and hybridized. An itinerant microwave field and a travelling optical field can be coupled through the hybrid system, where the microwave field is coupled to the hybrid system through the cavity mode, while the optical field addresses the hybrid system through the Kittel mode via Faraday and inverse Faraday effects. The conversion efficiency is theoretically analyzed and experimentally evaluated. The possible schemes for improving the efficiency are also discussed.

quant-ph↗