We present the design, fabrication, and characterization of a monolithic, segmented, three-dimensional linear Paul ion trap for quantum science applications. The trap is fabricated from a single fused-silica block using selective laser-induced etching (SLE) and is subsequently metallized, forming electrodes isolated by self-shadowing trench structures without the need for layer alignment or external shadow masks. The segmented electrodes allow for shaping of the axial potential, enabling the creation of anharmonic potential wells, such as those required for equidistant ion strings. In addition, they enable shuttling and splitting of ion chains. We discuss key design choices and SLE-imposed constraints on achievable feature sizes, and evaluate electron-beam evaporation and magnetron sputtering as metallization approaches. Across two independent experimental setups, we demonstrate stable trapping and control of linear chains of up to 33
40Ca
+ ions, including approximately equally spaced configurations. The measured secular frequencies in both traps agree with boundary-element simulations at the percent level, with residual deviations attributed to stray electric fields in the presence of anharmonic axial potentials, rather than fabrication imperfections. We measure axial micromotion field strengths on the order of 100 V/m along the trap axis, in approximate agreement with simulations. For radial mode frequencies near 2 MHz and an ion-electrode distance of 300 um, we measure heating rates of the order of 10 quanta/s in all but one motional mode, which is elevated by a technical noise source. The presented trap design is thus suitable for a wide range of quantum science applications and demonstrates the viability of SLE for the fabrication of finely segmented, monolithic, three-dimensional ion traps.
Monolithic three-dimensional (3D) Paul traps combine the high-precision microfabrication of two-dimensional (2D) chip traps with the deep trapping potentials and low heating rates characteristic of macroscopic 3D Paul traps, which are typically machined by traditional means and mechanically assembled. However, achieving low motional heating rates and optical access with a high numerical aperture (NA) while maintaining the high radio-frequency (RF) voltages required for trapping heavy ionic species, such as Yb
+ and Ba
+, remains a significant technical challenge. In this work, we present a fused-silica, monolithic segmented 3D Paul trap with an ion-electrode distance of 250
μm, and stable operation at high RF voltages. We benchmark the performance of the trap using Yb
+ ions, demonstrating axially homogeneous trapping potentials spanning over 200
μm about the axial center of the trap, high multi-directional optical access (up to 0.7 NA), and radial motional heating as low as $\dot{\bar n}=1.1 \pm 0.1 $ quanta/s at radial trap frequencies about 3 MHz near room temperature. Furthermore, we observe a motional Ramsey coherence time,
T2, of about 95 ms for the radial center-of-mass mode. We demonstrate the generation of a two-qubit Bell state with a parity contrast of
99.3−1.5+0.7% with state preparation and measurement correction. These results establish fused-silica monolithic 3D Paul traps as a scalable, modular platform for quantum simulation, computation, metrology, and networking with heavy ionic species.
Monolithic three-dimensional (3D) Paul traps combine the high-precision microfabrication of two-dimensional (2D) chip traps with the deep trapping potentials and low heating rates characteristic of macroscopic 3D Paul traps, which are typically machined by traditional means and mechanically assembled. However, achieving low motional heating rates and optical access with a high numerical aperture (NA) while maintaining the high radio-frequency (rf) voltages required for trapping heavy ionic species, such as Yb + and Ba + , remains a significant technical challenge. In this work, we present a fused silica, monolithic segmented 3D Paul trap with an ion-electrode distance of 250 μ m , and stable operation at high rf voltages. We benchmark the trap’s performance using Yb + ions, demonstrating axially homogeneous trapping potentials spanning over 200 μ m about the trap’s axial center, high multidirectional optical access (up to 0.7 NA), and radial motional heating as low as n ¯ ˙ = 1.1 ± 0.1 quanta / s at radial trap frequencies about 3 MHz near room temperature. Furthermore, we observe a motional Ramsey coherence time, T 2 , of about 96 ms for the radial center-of-mass mode. We demonstrate the generation of a two-qubit Bell state with a parity contrast of 99.3 − 1.5 + 0.7 % with state preparation and measurement correction. These results establish fused-silica monolithic 3D Paul traps as a scalable, modular platform for quantum simulation, computation, metrology, and networking with heavy ionic species.
Segmented linear ion trap arrays are versatile devices that are increasingly used to study quantum physics and demonstrate the fundamental principles of quantum information processing. Traps with three-dimensional (3-D) electrode geometries can create a superior confining potential for ions. However, the realization of a monolithic 3-D microchip trap with scalable fabrication technology remains challenging. In this paper the microfabrication of a monolithic array of 3-D ion microtraps in a semiconductor chip is presented. The electrode structure is formed by micromachining a silica-on-silicon wafer and metallizing the dielectric with gold. The fabrication method uses conventional semiconductor wafer processing tools and techniques. The specific operating characteristics which demonstrate the suitability of the chosen material system and fabrication process are presented.
A design is proposed for a novel ion trap quantum processor chip, microfabricated using a process based on planar silica-on-silicon techniques. The trap electrodes are of gold-coated silica and are spaced by highly doped silicon in a monolithic structure. This design allows a unit aspect-ratio trap with an ion-electrode separation below 100 μm, when using current fabrication techniques. The trapping potential is modelled and the operating parameters required to achieve motional frequencies of a few MHz are calculated. RF loss and the resultant heating of the trap chip are not found to be a factor limiting the trap's operation. This monolithic unit aspect-ratio trap is therefore expected to exhibit a deep potential well, high trap efficiency, and a low RF loss, when compared to other microfabricated traps. This technological approach is in principle scaleable to complex devices, and may form the basis for large-scale ion trap quantum processors.
Selective Laser-induced Etching (SLE) is a manufacturing process which enables the fabrication of three-dimensional parts from transparent materials with unique freedom of geometry and high precision. First, the outer contour of the part is inscribed in the material using focused ultrashort pulsed laser radiation. Second, the modified design is exposed from the bulk material using wet chemical etching. We analyze the possibility of using SLE for the machining of next generation fused silica ion traps suitable for quantum computing. Such ion traps require an enhanced functionality in combination with reduced error sources and a reproducible manufacturing process. Ion trap designs with three-dimensional features in the micrometer regime are developed to meet these requirements. Challenges of the SLE process arising from the ion trap design and its dimensions are discussed. Different process strategies to fabricate single ion trap components as well as complete ion traps are examined. We demonstrate that next generation ion traps can be machined using SLE and outline the way towards a fabrication on wafer level.