Tiny Motors for Quantum Dots express
A tiny motor bends with electricity and stretches an invisible spring. Such motors, piezoelectric actuators, are needed to stretch or squeeze quantum dots, making them emit pairs of entangled photons. Previously, they were made using complex methods, but now everything can be cut out with a single laser.
The laser fires ultrashort pulses — in femtoseconds, quadrillionths of a second. It vaporizes material without heating neighboring areas. First, the substrate is thinned, then metal traces are cut, and finally the actuator itself. The key innovation is local thinning: the material becomes thinner only where needed. This allows making devices smaller and operating at lower voltages.
Previously, they cut with a laser of a single wavelength; now they use ultraviolet, the third harmonic. Edges come out cleaner, shapes more precise. It's like cutting paper not with scissors but with a sharp knife: fewer burrs, better fit. As a result, strain from the actuator transfers to the quantum dot more efficiently, and the actuator itself holds more reliably.
This approach paves the way for chips where multiple quantum light sources live on a single crystal. Each can be tuned individually by stretching or squeezing its own quantum dot. This is a step toward quantum computers and secure communication.
Original abstract
as written by the authors arXiv:2601.09476
This article presents a novel fabrication route for miniaturized piezoelectric actuators that relies exclusively on processes based on femtosecond (fs) laser ablation. Previous work has already demonstrated that fs-lasers are uniquely suited for the fabrication of piezoelectric actuators based on PMN-PT, which are required for multiaxial strain-tuning of quantum dots (QDs) to enable, e.g. the generation of highly entangled photon pairs. Building on these foundations, the present work advances actuator performance and capabilities by introducing a local thinning strategy. This approach allows the realization of smaller devices, which in turn enables lower operating voltages, while simultaneously offering the possibility of integrating multiple quantum light sources on a single chip. The article provides a detailed description of the full fabrication chain, entirely based on fs-laser processing steps, from substrate thinning to metal layer structuring and final device definition. A particular focus is placed on the final cutting process, where the implementation of a third-harmonic ultraviolet (UV) fs-laser wavelength significantly improves edge quality and shape definition compared to the second harmonic (SH) wavelength used in previous work. The device fabricated through the combination of local thinning and UV-based cutting promises not only to enhance the efficiency of strain transfer but also to ensure the mechanical stability required for practical applications. These results establish fs-laser-based fabrication as a versatile and scalable method for next-generation piezoelectric actuators, paving the way for advanced strain-engineering approaches in semiconductor quantum optics and integrated quantum photonics.
A femtosecond is to a second what a second is to 31.7 million years.