quantum phenomena at room temperature
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A Breakthrough in the Control of Quantum Phenomena at Room Temperature Has Been Achieved, Researchers Say

Quantum physics and mechanical engineering have been united in a breakthrough method allowing the control of quantum phenomena at room temperature, according to the findings of a pioneering new study.

In quantum mechanics, observing and controlling quantum phenomena has traditionally only occurred under conditions where temperatures approach absolute zero. Theoretically the coldest temperature attainable and roughly equivalent to around -459.67 Fahrenheit, absolute zero is the point at which matter becomes so cold that the motion of particles would cease.

Although allowing for easier detection of quantum effects, reaching such astoundingly cold temperatures is not easy, and has limited applications and studies involving quantum technologies.

“Reaching the regime of room temperature quantum optomechanics has been an open challenge since decades,” says Tobias J. Kippenberg, the co-author of a new study that, based on its findings, could finally present practical ways of overcoming such challenges.

According to Kippenberg, the new work has brought what physicists call Heisenberg’s microscope—once only realized as a theoretical model—into reality.

The new research, co-authored with Kippenberg’s colleague Nils Johan Engelsen, was the focus of a new study published in the journal Nature.

In their experiment, the team succeeded in producing a novel, ultra-low noise optomechanical system that enabled studies at the convergence of light and mechanical motion and allowed the team to examine light’s influence on moving objects through its precise manipulation.

Attempting to achieve this at room temperature has always been difficult on account of thermal noise, the heat that arises from the motion of particles, and impedes observations of the dynamics of the quantum world.

To overcome the thermal noise issue, Kippenberg and Engelsen used special mirrors that reflect light back and forth within a small space, known as cavity mirrors, to effectively trap photons. Featuring patterns comprised of photonic crystalline structures, the cavity mirrors allowed the light they “trapped” to be manipulated to interact with the system’s mechanical elements.

“By using phononic-crystal-patterned cavity mirrors, we reduce the cavity frequency noise by more than 700-fold,” the study’s authors write in a recent paper describing their findings.

“In this ultralow noise cavity, we insert a membrane resonator with high thermal conductance and a quality factor (Q) of 180 million, engineered using recently developed soft-clamping techniques,” the authors report.

The experiment also employed a tiny mechanical oscillator to interact with light within the “trapped” cavity between the mirrors. Using this clever method of isolation, subtle quantum phenomena were able to be discerned even at room temperature.

The mechanical oscillator they used was “the culmination of many years of effort,” according to Engelsen, who said it allowed them “to create mechanical oscillators that are well-isolated from the environment.”

Among the study’s achievements had also been the successful use of a phenomenon known as optical squeezing, which leverages Heisenberg’s principle by manipulating the phase, intensity, or other properties of light in ways that help lessen the amount of fluctuation that occurs within a given variable, which thereby increases fluctuations in another.

In their experiment, the attainment of optical squeezing under such conditions allowed the team to show that control and observation of quantum phenomena in a macroscopic system could indeed be achieved at room temperature.

“The system we developed might facilitate new hybrid quantum systems where the mechanical drum strongly interacts with different objects, such as trapped clouds of atoms,” said Alberto Beccari, lead author of the new study.

“These systems are useful for quantum information, and help us understand how to create large, complex quantum states,” Beccari added.

Many potential applications could result from the new research, which might include a broadening of access to quantum optomechanical systems, which could help to facilitate quantum measurement and quantum mechanics at macroscopic scales.

The new paper, “Room-temperature quantum optomechanics using an ultralow noise cavity,” by Guanhao Huang, Alberto Beccari, Nils J. Engelsen, and Tobias J. Kippenberg, was published on February 14, 2024, in the journal Nature.

Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.