McGill researchers take a major step toward ‘sound lasers’ to transform communications and medicine

A team of Canadian researchers has unveiled a quantum device capable of generating precisely controlled bursts of sound-like particles known as phonons, a breakthrough that could eventually lead to a new class of technologies including sound-based lasers, advanced medical diagnostics, ultra-sensitive sensors, and novel communications systems.

The research, led by scientists at Montreal’s McGill University in collaboration with Canada’s National Research Council (NRC), pushes the boundaries of quantum physics and may force researchers to rethink some aspects of how energy moves through advanced materials. While the work is highly technical, its implications are surprisingly broad. Just as lasers revolutionized telecommunications, computing, and medicine through the controlled manipulation of light, scientists hope phonon-based devices could eventually do something similar using sound and mechanical vibrations.

Creating sound at the quantum level

The study, published in Physical Review Letters, describes how researchers generated phonons by driving electrons at extremely high speeds through an ultra-thin two-dimensional crystal structure cooled to temperatures only fractions of a degree above absolute zero.

Phonons are often described as the quantum equivalent of sound waves. They represent tiny packets of vibrational energy that move through materials, similar to how photons represent packets of light. Understanding and controlling phonons has become an important area of research because they influence heat transfer, electronic performance, and information transmission in advanced materials.  The McGill-led team discovered that when electrons were forced through an atomically thin channel fast enough, they shed excess energy not as random heat but as predictable and controllable bursts of phonons.

For researchers seeking practical quantum technologies, predictability is the critical factor.

“The researchers found that these phonons can be generated in predictable and tuneable patterns,” according to McGill University, representing a key advance toward devices that can manipulate sound at the quantum scale.

The experiments were conducted at temperatures between approximately 10 milli-Kelvin and 3.9 Kelvin, conditions thousands of times colder than a typical Canadian winter. At these temperatures, electrons behave in highly ordered ways, making subtle quantum effects easier to observe.  According to McGill physicist Michael Hilke, one of the study’s authors, the team intentionally pushed electrons beyond what might be viewed as a quantum “sound barrier.”

“At absolute zero temperatures, no sound is created unless electrons travel collectively at the speed of sound or above,” Hilke explained. The researchers observed behaviour that extended beyond existing theoretical predictions, suggesting that current models may need revision.

The finding is important because it indicates that electrons can remain energetically “hot” even when the surrounding crystal is extremely cold, resulting in previously unanticipated phonon generation mechanisms.

A Canadian contribution to quantum technology

The work also highlights Canada’s growing role in quantum science. Although the material used in the device was synthesized at Princeton University, the device itself was designed, constructed, and analysed through collaboration between McGill University and the National Research Council of Canada. Canada has invested heavily in quantum technologies over the past decade, supporting research in quantum computing, quantum communications, and quantum materials. Efforts such as the federal government’s National Quantum Strategy aim to position Canada as a global leader in the sector.

Perhaps the most intriguing aspect of the research is its connection to phonon lasers. Conventional lasers generate highly coherent beams of light. A phonon laser would instead generate highly organized and precisely controlled vibrations or sound waves. Scientists sometimes refer to such devices as “sasers,” an acronym for Sound Amplification by Stimulated Emission of Radiation. Unlike everyday sound, these vibrations could operate at extremely high frequencies and microscopic scales.

This capability could open entirely new technological possibilities. In environments where electromagnetic signals perform poorly, such as underwater settings, controlled sound waves can often travel much more effectively.

“Modern communication is largely based on light, including electromagnetic waves and electrical currents. In a medium such as oceans, sound can travel, whereas light and electrical currents cannot,” Hilke noted.

The implications extend beyond communications for the sound already plays a significant role in medicine through ultrasound imaging, diagnostic systems, and various therapeutic technologies. Researchers believe future phonon-based devices could allow even more precise biological measurements and imaging techniques.  Because sound waves interact differently with biological tissues than light does, phonon technologies may provide new ways to investigate cells, tissues, and biomaterials.

The team’s next objective is to explore whether the device can be constructed using alternative materials, particularly graphene. Graphene’s exceptional electrical and thermal properties could allow the technology to operate at even higher speeds and efficiencies.  Researchers are also interested in understanding why the observed behaviour differs from existing theoretical predictions.