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Nanostrings Open the Door to Macroscopic Quantum Phenomena

Researchers at TU Delft and Brown University have created string-like resonators that can vibrate longer at room temperature than any previously known solid-state device, reaching what is now only possible at absolute zero temperatures. The results were reported in Nature Communications.

Nanostrings Open the Door to Macroscopic Quantum Phenomena

Image Credit: Golden Wind/

Their research pushes the boundaries of nanotechnology and machine learning, producing some of the world’s most sensitive mechanical sensors.

The newly generated nanostrings have the best mechanical quality factors ever reported for any clamping object in room temperature conditions, in this instance clamped to a microchip. This makes the technique appealing for incorporation into current microchip platforms.

Mechanical quality factors represent how well energy is retained in a vibrating object. These strings are specially designed to trap vibrations, preventing their energy from leaking out.

A 100 Year Swing on a Microchip

Imagine a swing that, once pushed, keeps swinging for almost 100 years because it loses almost no energy through the ropes. Our nanostrings do something similar but rather than vibrating once per second like a swing, our strings vibrate 100,000 times per second. Because it’s difficult for energy to leak out, it also means environmental noise is hard to get in, making these some of the best sensors for room temperature environments.

Richard Norte, Associate Professor, Delft University of Technology

This breakthrough is critical for researching macroscopic quantum processes at room temperature, which were previously obscured by noise.

While the weird laws of quantum mechanics are usually observed only in single atoms, the nanostrings’ ability to isolate themselves from everyday heat-based vibrational noise allows them to reveal their own quantum signatures, despite being composed of billions of atoms. In everyday environments, this capability could have intriguing applications for quantum-based sensing.

Extraordinary Match Between Simulation and Experiment

Our manufacturing process goes in a different direction with respect to what is possible in nanotechnology today.

Dr Andrea Cupertino, Postdoctoral Researcher, Department of Precision and Microsystems Engineering, Delft University of Technology

The strings are 3 centimeters long and 70 nanometres thick, but when scaled up, this would be akin to producing glass guitar strings suspended half a km with nearly no sag.

This kind of extreme structures are only feasible at nanoscales where the effects of gravity and weight enter differently. This allows for structures that would be unfeasible at our everyday scales but are particularly useful in miniature devices used to measure physical quantities such as pressure, temperature, acceleration and magnetic fields, which we call MEMS sensing,” Dr Cupertino added.

The nanostrings are constructed utilizing sophisticated nanotechnology processes pioneered at TU Delft, which push the limits of how thin and long suspended nanostructures can be created.

A key aspect of the collaboration is that these nanostructures can be fabricated with such precision on a microchip that there is an extraordinary match between simulations and experiments. This alignment allows simulations to serve as the data for machine learning algorithms, reducing the need for costly experiments.

Our approach involved using machine learning algorithms to optimize the design without continuously fabricating prototypes.

Dr. Dongil Shin, Study Lead Author and Postdoctroal Researcher, Department of Precision and Microsystems Engineering, Delft University of Technology

To improve the efficiency of designing these large, detailed structures, machine learning algorithms intelligently utilized insights from simpler, shorter string experiments to refine the designs of longer strings, making the development process both economical and effective.

Norte noted that the success of this project highlights the fruitful collaboration between experts in nanotechnology and machine learning, emphasizing the interdisciplinary nature of cutting-edge scientific research.

Inertial Navigation and Next-Generation Microphones

The consequences of these nanostrings transcend beyond basic science. They provide interesting new avenues for merging highly sensitive sensors with ordinary microchip technology, possibly leading to novel vibration-based sensing techniques.

While this preliminary research focuses on strings, the concepts can be expanded to more complicated devices to monitor other crucial characteristics such as acceleration for inertial navigation or something resembling a vibrating drumhead for next-generation microphones.

This study highlights the wide range of possibilities for integrating nanotechnology developments with machine learning to create new technological frontiers.

Journal Reference:

Liu, Y.-X., et. al. (2024) Quantum interference in atom-exchange reactions. Science. doi:10.1126/science.adl6570.

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