Within the realm of quantum mechanics, the flexibility to look at and control quantum phenomena at room temperature has long been elusive, especially on a big or “macroscopic” scale. Traditionally, such observations have been confined to environments near absolute zero, where quantum effects are easier to detect. However the requirement for extreme cold has been a serious hurdle, limiting practical applications of quantum technologies.
Now, a study led by Tobias J. Kippenberg and Nils Johan Engelsen at EPFL, redefines the boundaries of what is possible. The pioneering work blends quantum physics and mechanical engineering to attain control of quantum phenomena at room temperature.
“Reaching the regime of room temperature quantum optomechanics has been an open challenge since a long time,” says Kippenberg. “Our work realizes effectively the Heisenberg microscope — long regarded as only a theoretical toy model.”
Of their experimental setup, published in Nature, the researchers created an ultra-low noise optomechanical system — a setup where light and mechanical motion interconnect, allowing them to check and manipulate how light influences moving objects with high precision.
The most important problem with room temperature is thermal noise, which agitates delicate quantum dynamics. To reduce that, the scientists used cavity mirrors, that are specialized mirrors that bounce light backwards and forwards inside a confined space (the cavity), effectively “trapping” it and enhancing its interaction with the mechanical elements within the system. To scale back the thermal noise, the mirrors are patterned with crystal-like periodic (“phononic crystal”) structures.
One other crucial component was a 4mm drum-like device called a mechanical oscillator, which interacts with light contained in the cavity. Its relatively large size and design are key to isolating it from environmental noise, making it possible to detect subtle quantum phenomena at room temperature. “The drum we use on this experiment is the culmination of a few years of effort to create mechanical oscillators which are well-isolated from the environment,” says Engelsen.
“The techniques we used to take care of notorious and sophisticated noise sources are of high relevance and impact to the broader community of precision sensing and measurement,” says Guanhao Huang, certainly one of the 2 PhD students leading the project.
The setup allowed the researchers to attain “optical squeezing,” a quantum phenomenon where certain properties of sunshine, like its intensity or phase, are manipulated to cut back the fluctuations in a single variable on the expense of accelerating fluctuations in the opposite, as dictated by Heisenberg’s principle.
By demonstrating optical squeezing at room temperature of their system, the researchers showed that they may effectively control and observe quantum phenomena in a macroscopic system without the necessity for very low temperatures. Top of Form
The team believes the flexibility to operate the system at room temperature will expand access to quantum optomechanical systems, that are established testbeds for quantum measurement and quantum mechanics at macroscopic scales.
“The system we developed might facilitate latest hybrid quantum systems where the mechanical drum strongly interacts with different objects, resembling trapped clouds of atoms,” adds Alberto Beccari, the opposite PhD student leading the study. “These systems are useful for quantum information, and help us understand create large, complex quantum states.”
