Using lasers to control vibrations
Using new techniques, Yale researchers have demonstrated the ability to use lasers to cool quantized vibrations of sound within massive objects to their quantum ground state, the lowest energy allowable by quantum mechanics. This breakthrough could benefit communications, quantum computing, and other applications. The results are published in Nature Physics.
Using a micro-scale resonator fashioned from crystalline quartz, a research team led by Professor Peter Rakich demonstrated that they could control the vibrations within these macroscopic mechanical objects at the quantum level using light. Rakich notes that, in the quantum realm, “massive” is a relative term. In this case, 10 micrograms of material in the acoustic wave motion, or an object that’s a bit smaller than a grain of sand. At the atomic scale, however, this corresponds to an enormous number of atoms (100 quadrillion) moving in quantum-coherent fashion.
This a big advance, since prior methods that use light to control motion at the quantum level have been limited to objects that are about a million times smaller. The larger scale of this system is important because this increased size translates to longer coherence times - that is, the duration of time that quantum information can maintain its quantum properties before decaying.
Increasing coherence times is a critical challenge for quantum scientists, and one of the barriers to making practical quantum computers. In this case, increased size translates to longer coherence because a smaller proportion of the atoms resides at the surface, where things can get tricky (even by quantum’s very tricky standards).
“It’s notoriously difficult to control various interactions that occur at surfaces,” says Rakich, the Donna Dubinsky Professor of Applied Physics. That’s why the Rakich lab’s approach works so well – using light to access sound waves within the bulk of a crystal, they greatly reduce surface interactions, effectively protecting this system from unwanted quantum decoherence.
Hagai Diamandi, a former postdoctoral associate in Rakich’s lab and lead author of the paper, noted that the system provides excellent material properties, without many of the drawbacks of conventional methods. “The structure of the micro-scale resonator is very robust against unwanted heating, making it much easier to use this system as a quantum memory,” says Diamandi, now an assistant professor at Hebrew University.
How they did it
Other labs have created crystalline resonators that support bulk acoustic phonons before, but they were designed to interact with electrical signals, typically providing access to much lower-frequency phonons.
“We have developed a very different type of bulk acoustic resonator that permits access to very high-frequency phonons using light,” Rakich says. They were able to enhance the interaction between light and the massive phonons within the resonator using a device known as an optical Fabry-Perot resonator, which uses high-reflectivity mirrors to enhance the light field in the crystalline resonator. With this system, they were able to use lasers to cool the quantized vibrations (or phonons) within these objects to their lowest state of energy. In doing so, they were able to stabilize the phonons and enhance their quantum properties.
“Having a system that can precisely control phonons while maintaining their unique properties opens up exciting possibilities for advancing the field of quantum research,” says Diamandi.
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Published Date
Aug 11, 2025
