A Charge-Particle-Free Atomic Source for Cryogenic Ion Traps Based on Microheater-Driven Reduction of SrCO₃

For surface-electrode ion traps for quantum information processing, anomalous heating is a major factor limiting quantum-gate fidelity and long coherence times. This effect is particularly severe when the distance between ion and electrode is small. Cryogenic operation is known to be an effective approach to suppress anomalous heating. However, atomic sources used for ion generation and loading in cryostats must satisfy strict requirements including low thermal load and cleanliness. Conventional resistively heated ovens can provide atomic flux, but their large heat dissipation makes them incompatible with cryogenic systems. In addition, strontium atoms are rapidly oxidized in air, which complicates handling it in normal condition. Laser ablation enables fast and localized atomic delivery with a small average heat load, but it produces energetic charged particles that can charge or contaminate electrode surfaces. In our surface-electrode traps, this effect has led to severe difficulties for trapping ions.

In this work, we develop an atomic source suitable for cryogenic ion traps that operates with a low thermal load. We propose and demonstrate a method based on chemical reduction on a microfabricated heater. A solid-state mixture of strontium carbonate and aluminum is placed on the microheater, and neutral strontium atoms are generated through controlled local heating due to thermite reaction.

Sr atoms emitted from the micro heater are detected by using fluorescence spectroscopy on the 461 nm resonant transition. It was confirmd with gaussian fit to the measured fluorescence spectrum that the atoms have a velocity distribution suitable for ion loading. Repeated operation of the microheater shows that it can generate atoms thousands cycles.

These results show that the proposed microheater-based SrCO₃ reduction source is an effective atomic source for cryogenic surface-electrode ion traps. Measurements to verify the absence of charged-particle emission is currently in progress and will be reported.