The lasers utilize individual particles of vibration or sound to measure quantum mechanics and gravity.
When lasers were invented in the 1960s, they opened new avenues for scientific discovery and everyday applications from scanners at the grocery store to corrective eye surgery. Conventional lasers control photons-individual particles of light-but over the past 20 years, scientists have invented lasers that control other fundamental particles, including phonons-individual particles of vibration or sound. Controlling phonons could open even more possibilities with lasers, such as taking advantage of unique quantum properties like entanglement.
A new squeezed phonon laser developed by researchers at the University of Rochester and Rochester Institute of Technology provides precise control over phonons at the nanoscale level. This could give new insights into the nature of gravity, particle acceleration, and quantum physics. In a paper in Nature Communications, the researchers describe how they coax these individual particles of mechanical motion to behave like a laser.
Nick Vamivakas, the Marie C. Wilson and Joseph C. Wilson Professor of Optical Physics with the URochester Institute of Optics, and his collaborators first demonstrated a phonon laser by trapping and levitating phonons with an optical tweezer in a vacuum in 2019. But to make this technology useful for extremely accurate measurements, they had to overcome a key obstacle fundamental to both photon and phonon lasers: noise, or unwanted disturbances that make a signal difficult to accurately read.
"While a laser looks to the naked eye like a steady beam, there's actually a lot of fluctuation, which causes noise when you're using lasers for measurement," says Vamivakas. "By pushing and pulling on a phonon laser with light in the right way, we can reduce that phonon laser fluctuation significantly."
Specifically, the researchers were able to squeeze or reduce the thermal noise intrinsic to the phonon laser. Vamivakas says that noise reduction provides the ability to measure acceleration more accurately than techniques that use photon lasers or radio frequency waves.
Vamivakas envisions researchers using the phonon laser to obtain pinpoint accurate measurements of gravity and other forces, which could be important in applications such as navigation. Scientists have envisioned quantum compasses as more accurate, "unjammable" alternatives to GPS navigation that do not require the use of satellites, and Vamivakas is intrigued by seeing if the phonon laser could be a step toward such systems.
The research was supported by the National Science Foundation.
