Trapped-Ion Quantum Computing LaboratoryPrecision Ion Trapping and Control: Paving the Way for the Future of Quantum Computing

An ion trap is a device that uses oscillating electric fields to confine charged particles. At the Trapped-Ion Quantum Computing Laboratory, the research team works with naturally occurring ytterbium-171 atoms. By ionizing one of the atom's outermost electrons, the atom becomes electrically charged. The ion is then precisely trapped in a vacuum using radio-frequency (RF) fields generated by three pairs of electrodes, with laser cooling applied to stabilize and localize the ion. As more ions are trapped, adjusting the electric potential distribution allows them to naturally align into a linear ion array.

Trapped ions of the same isotope are physically identical, which is a gift from nature. This eliminates the fabrication variability that affects many artificial qubit platforms, making trapped ions ideal qubit candidates. Because quantum states are extremely delicate, experiments must be performed under ultra-high vacuum conditions, which are comparable to outer space, in order to minimize interference caused by environmental noise and stray particles.

High particle temperatures lead to increasingly random and vigorous motion, which undermines the precision of quantum state storage and control. However, in a vacuum, the absence of friction means that ions cannot lose energy naturally. Their motion cannot be reduced passively to levels near absolute zero.

To address this challenge, the research team employs laser cooling. While illuminated by red-detuned laser beams, fast-moving ions absorb photons traveling against their motion. Momentum transfer reduces their motion, cooling them to near absolute zero within milliseconds. Meanwhile, the surrounding components, including the vacuum chamber walls, remain at room temperature. This greatly alleviates the otherwise stringent cryogenic requirements of quantum computing hardware.

Another advantage of ion qubits is their exceptional connectivity. Within the same array, ions interact via shared vibrational modes, enabling logic operations between any pair of qubits. With precise electrode control, ions can even be shuttled between arrays, supporting scalable and modular quantum architectures.

By contrast, artificial qubit platforms are constrained by physical wiring layouts, and thus the interactions are limited to adjacent qubits, resulting in significantly lower connectivity.

From Individual Ions to Ion Arrays

The Trapped-Ion Quantum Computing Laboratory was inaugurated on October 15, 2023. As equipment was gradually installed, the research team began assembling the ion trap experimental system. After a year of dedicated work, lab researchers successfully trapped clusters of ytterbium ions in October 2024 and, by year’s end, obtained the first image of a single ion. Within weeks, they achieved a breakthrough and created a stable ion array. By mid-2025, the team was able to produce stable arrays containing more than fifty ions.

The process appeared straightforward, but it was full of challenges.

For instance, environmental fluctuations can cause laser frequency drift, requiring active frequency stabilization to lock the laser to a precise reference. The laser’s linewidth must also be tightly controlled to prevent unintended state transitions in the ions.

In addition, quantum state readout requires efficient collection of the faint ion fluorescence emitted by ions after excitation. By tuning the laser to a specific frequency, only ions in the “1” state are excited, while those in the “0” state remain unaffected. The process requires carefully designed optical paths, lens arrangements, spatial resolution tuning, low-light amplification, and signal processing techniques. These elements work together to extract the fluorescence profile of each ion, allowing accurate determination of its quantum superposition between 0 and 1.

Control Precision and Connectivity

Beyond qubit count, the team places particular emphasis on the precision of ion control and the connectivity between qubits, both considered core performance metrics. Although the team has successfully trapped more than fifty ions to date, only those whose quantum states can be controlled with high precision qualify as true qubits. Consequently, the team’s short-term goal remains focused on achieving high-fidelity control over 5 to 10 qubits.

The ion trap core has also continued to evolve. In 2022, the team introduced a first-generation single-zone blade-type design, followed by a second-generation multi-zone layered architecture in 2023. The first-generation core has already been installed in experiments, successfully capturing and manipulating ion arrays to demonstrate its effectiveness.

Meanwhile, the multi-zone trap design is still under optimization. According to Dr. Guin-Dar Lin, Director of the Trapped-Ion Quantum Computing Laboratory, experiments involving both the first- and second-generation cores are expected to run in parallel between 2025 and 2026, each tasked with different roles such as ion control and system validation.

The evolution from the first- to the second-generation ion trap marks a shift from the simple to the complex. The first-generation core features a relatively simple and stable design, suitable for testing, training, and providing calibration data and physical parameters. The second-generation trap adopts a multi-zone architecture, in which the trap is segmented into multiple regions with independently applied voltages. This allows researchers to dynamically reshape the potential landscape to precisely control ion movement for different tasks, such as bringing specific ions together to perform logic operations or separating them for storage when interaction is not required.

Current first- and second-generation prototypes rely on precision machining, which makes the system difficult to scale. To expand from tens of qubits to hundreds of thousands or even millions, more stable semiconductor processes will be required so as to achieve system miniaturization and optical integration.

From Ion Trap Experiments to Universal Quantum Computers

Quantum computer performance is evaluated through multiple metrics that factor in qubit count, connectivity, and coherence time. Among competing platforms, trapped-ion systems stand out in the current “noisy intermediate-scale quantum” (NISQ) era for their superior connectivity and coherence. Looking ahead to scalable quantum computing architectures, silicon photonics presents a technically demanding but promising pathway.

To explore how future semiconductor processes might be applied to ion-trap systems, the Trapped-Ion Laboratory has collaborated with the Semiconductor Research Center, Academia Sinica, and National Yang Ming Chiao Tung University. The partnership focuses on forward-looking development, with silicon photonics as a key enabling technology.

At the million-qubit scale, assigning a dedicated laser source to each ion is not only impractical but also prohibitively expensive. Silicon photonics offers a scalable solution by leveraging semiconductor processes to produce integrated waveguides on the substrate. These waveguides route light beneath target ions, couple it into free space, and focus it precisely onto individual ions.

However, the light required to control specific ions often falls within frequency ranges that are strongly absorbed by common silicon photonic materials, leading to low efficiency and thermal management issues. Globally, the use of silicon photonics is still at its early stages of development. Thus, integrating silicon photonics into ion-trap systems continues to pose significant challenges. These include identifying new materials with mature processes and specific wavelengths to designing components that meet system requirements.

Looking ahead, Dr. Guin-Dar Lin outlines a staged roadmap for the Trapped-Ion Laboratory.

Short-term goal (by 2027): Building a universal ion-trap quantum computer prototype with 5 to 10 qubits. “Universal” refers to general-purpose hardware, such as a classical computer, that can execute diverse tasks through programmable code rather than being limited to a single function. However, given the limited qubit count, such a prototype will not yet be able to solve practical problems.

Medium-term goal: Developing the key technologies required for scalable quantum computing architectures. This includes transitioning from current 3D ion-trap structures to 2D designs, namely, ion-trap chips fabricated using semiconductor processes, ion-shuttling techniques, and the integrated optical and electronic components for qubit control. Ultimately, the ion-trap system will be further miniaturized and modularized, with enhanced stability and connectivity.

Long-term goals: Establishing scalable architectures through stable, modular interconnections to support hundreds, thousands, or even tens of thousands of effective qubits. As hardware technologies mature, the laboratory will collaborate with the Quantum Computing Research Center to implement fault-tolerant, error-corrected algorithms, delivering the computational power needed for advances in AI, intelligent platforms, energy storage, and pharmaceutical development.

Cultivating Expertise and Building Ecosystems

Taiwan has long prioritized research areas closely tied to existing industrial sectors. However, emerging sciences such as quantum technologies, optics, atomic and molecular physics remain comparatively underdeveloped. With the quantum industry chain still in its formative stages and the pull of established overseas quantum research hubs and semiconductor sectors, cultivating and retaining domestic quantum talent remains a significant challenge.

According to Dr. Guin-Dar Lin, the current team at the Trapped-Ion Laboratory is composed primarily of physicists with expertise in theoretical and experimental quantum optics and atomic physics. However, quantum computing development is inherently interdisciplinary, and the lab has consistently welcomed talent from electrical engineering, electronics, materials science, and computer science. By generating increasingly mature research outcomes, the lab hopes to build momentum and attract more aspiring researchers to the quantum technology field.

“Quantum computing is undoubtedly the ‘holy grail’ of the next generation,” Dr. Lin emphasized. “Its advancement hinges on repeated trial and error, accumulated experience, and the high-level integration of talent, resources, and technologies. The Trapped-Ion Laboratory serves as a crucial experimental platform for Taiwan’s industry. Moving forward, the laboratory will continue to invest resources and connect domestic and international academic, governmental, and industrial expertise to achieve results recognized by the global industry.”

Quantum computing is widely regarded as a key technology for surpassing the current computational limits, with ion trapping emerging as one of the most promising hardware platforms.

The establishment of the Trapped-Ion Laboratory not only demonstrates the industry’s commitment to advancing quantum technology but also establishes a critical foundation for Taiwan’s quantum ecosystem.