3D traps now host ion crystals for quantum simulation and networking

Microfabricated three-dimensional ion traps are now achieving electric field depths in the electron volt range, a performance leap enabling more stable ion confinement for quantum technologies. These monolithic 3D traps, built with micron-level precision, feature segmented electrodes that facilitate and maintain low heating rates through larger ion-electrode distances.

The fabrication process, using Translume Inc.’s femtoEtch process on fused silica, supports high voltages, over 450V peak to peak, and has been demonstrated with Yb+ ions, exhibiting heating rates of approximately 1 quanta per second. This platform offers robust operation and high photon collection efficiency, advancing the scalability of quantum simulation and networking.

Monolithic 3D Trap Design for Heavy Ion Species

The fabrication of three-dimensional ion traps now extends to heavier ionic species, specifically barium and ytterbium, critical for advancements in quantum information science. Previous monolithic 3D traps struggled to manipulate these heavier ions while maintaining performance characteristics, a limitation this work overcomes with a new design. This capability addresses a significant technical hurdle; heavier ions require shorter ion-electrode distances or higher radio frequency voltages to achieve comparable frequencies to lighter ions like beryllium or calcium.

Achieving this without compromising trap integrity or performance presented considerable fabrication challenges, including the need for robust radio frequency isolation and high-quality substrate materials. Reducing the distance between the ion and the electrode typically increases heating rates, which degrades the coherence of the ion’s motion, a vital factor for quantum applications. This new trap design, however, maintains a relatively large ion-electrode distance while achieving a low heating rate of approximately one quanta per second.

This performance is coupled with long motional Ramsey coherence times of around 96 milliseconds, demonstrating improved stability for maintaining delicate quantum states. The trap’s geometry also allows for high multidirectional optical access, reaching a numerical aperture of 0.7, facilitating precise laser control and manipulation of the trapped ions. This configuration enables a broad range of quantum technology applications, extending beyond computing and simulation to include networking and metrology.

The resulting traps support axially homogeneous radial trapping potentials and demonstrate low excess micromotion, critical for maintaining the coherence of trapped ions. Benchmarking with Yb+ ions revealed heating rates as low as approximately 1 quanta per second, a performance level comparable to cryogenic ion traps.

Segmented Electrode Geometry Enables Zone-Based Control

The ability to individually control zones within a microfabricated ion trap is now realized through segmented electrode geometry, a design feature enabling more complex quantum operations. This precision fabrication, achieved with micron-level accuracy, allows for the creation of stable, reconfigurable trapping potentials critical for manipulating individual ions. The design moves beyond simple confinement, offering a pathway toward scalable quantum computing architectures by isolating and addressing specific ions within a larger chain.

These monolithic 3D traps use segmented electrodes to facilitate zone-based control, a capability enhanced by the trap’s physical structure. The trap’s geometry also contributes to low heating rates, a persistent challenge in ion trapping, by maximizing the distance between ions and electrodes. This design choice, coupled with the trap’s ability to achieve depths in the electron volt range, provides stronger confinement and improved stability for the trapped ions.

Low Heating Rates Achieved with Micron-Level Precision

This reduction in heating, a persistent obstacle to maintaining quantum coherence, stems from a deliberate design choice prioritizing greater separation between the ions and the trap’s electrodes. Larger distances minimize disruptive interactions that contribute to energy gain within the trapped ions, extending the duration of their quantum states. Fabrication repeatability, enabled by micron-level precision, supports the creation of segmented electrodes essential for zone-based quantum operations.

These electrodes allow for precise control over individual zones within the trap, facilitating manipulation of heavier ionic species with enhanced stability. The researchers report detailing their methodology for quantifying this performance improvement. This performance places the GEN3 trap among the lowest reported heating rates for room-temperature operation, rivaling those achieved with cryogenic cooling. The researchers demonstrated the ability to manipulate the heating rates of each radial mode frequency by inverting the sign of the “twist” voltage, offering an additional degree of control over the ion’s behavior.

Fused silica substrates, fabricated with Translume Inc.’s femtoEtch process, are used in the fabrication process.

Multidirectional Optical Access for Individual Addressing

The newest iteration of these microfabricated traps achieves 0.7 numerical aperture (NA) optical access, a feature critical for efficient state detection and single-ion manipulation within the device. This level of access surpasses many existing ion trap designs, enabling more precise control and measurement of individual ions. Maintaining these states is paramount, as heating degrades motional mode coherence, a vital factor for quantum information science, metrology and precision spectroscopy.

Fabrication repeatability, achieved through precision manufacturing at the micron level, allows for the creation of segmented electrodes within the 3D structure. This level of control is essential for scaling up quantum systems, as it allows for individual addressing and manipulation of ions within a larger crystal.

The demonstrated axial homogeneity and electrode segmentation enable operations with long ion chains, reducing calibration overhead and minimizing systematic errors in addressing, cooling, state readout, and gate performance. The small footprint and high optical access also position the trap as a strong candidate for integration with cavities and photonic chips, potentially boosting photon-collection rates for quantum networking protocols.

Axial Inhomogeneity Minimization for Ion Chain Stability

Accounting for capacitance asymmetry between radio frequency and direct current traces, the design of the latest microfabricated ion traps minimizes axial micromotion, a source of error in ion chain stability. These results demonstrate a high degree of control over the trapping potential and validate the effectiveness of the design modifications.

Performance Benchmarking Rivals Cryogenic Ion Traps

This milestone demonstrates robust operation at high radio frequency voltages exceeding $450V_{p}k$, enabling deeper trapping potentials and improved ion confinement. Researchers fabricated the trap from fused silica using a selective-laser etching process, resulting in a monolithic three-dimensional structure with segmented electrodes. The trap is fabricated by Translume Inc. using their femtoEtch process on a 2-mm-thick substrate of fused silica.

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