Researchers from Delft University of Technology managed to design a quantum sensor that doesn’t need to operate at temperatures near absolute zero. Combining nanotechnology and machine learning, topped off with a little inspiration from nature, they made a nanomechanical resonator that vibrates extremely well in isolation, without thermal noise affecting it. Being able to ditch the cryostats like that would make quantum devices more affordable.
Key to the device’s characteristics is its spiderweb design. “I realized spiderwebs are really good vibration detectors, in that they want to measure vibrations inside the web to find their prey, but not outside of it, like wind through a tree. So why not hitchhike on millions of years of evolution and use a spiderweb as an initial model for an ultra-sensitive device?” explains Richard Norte, assistant professor at TU Delft.
The exact design of the sensor was ‘picked’ from 150 different spiderweb designs by a Bayesian optimization algorithm. To the researchers’ surprise, the algorithm proposed a relatively simple design, which consists of only six strings put together in a deceivingly simple way. Nevertheless, simulations showed that the device could work at room temperature.
After further optimizing this design, assisted by computer modeling and machine learning, the researchers built a microchip sensor with an ultra-thin, nanometer-thick film made of silicon nitride. They tested the model by forcefully vibrating the microchip ‘web’ and measuring the time it takes for the vibrations to stop. The result was spectacular: a record-breaking isolated vibration at room temperature. Norte: “We found almost no energy loss outside of our microchip web: the vibrations move in a circle on the inside and don’t touch the outside. This is somewhat like giving someone a single push on a swing and having them swing on for nearly a century without stopping.”