In a new physics milestone, scientists report that a time crystal and an external system have been successfully linked for the first time.
The achievement, made by researchers at Aalto University’s Department of Applied Physics, marks the first demonstration of converting a time crystal—an unusual quantum system in which particles are in constant, repetitive motion in its ground state—into an optomechanical system.
A range of potential technological applications, including new high-precision sensors, quantum storage systems, and other innovative capabilities, could result from the research, led by Jere Mäkinen and detailed in a new paper appearing in Nature Communications.
A New First for Time Crystals
Conceptually similar to physical crystalline forms that occur in nature, time crystals were first proposed by Nobel Prize-winning physicist Frank Wilczek in 2012, who argued that comparable systems might also exist in time as well as in space.
Wilczek’s theory preceded the official experimental discovery of time crystals by just four years, which can be thought of as an unusual manifestation of matter whose motion repeats indefinitely.
In a recent study, Mäkinen, an Aalto University Academy Research Fellow, and his colleagues demonstrated that the properties of a time crystal could be altered, a feat never achieved before.
“Perpetual motion is possible in the quantum realm so long as it is not disturbed by external energy input, such as by observing it,” Mäkinen recently said. “That is why a time crystal had never before been connected to any external system.”
That is, until now.
“We did just that,” Mäkinen added, “and showed, also for the first time, that you can adjust the crystal’s properties using this method.”
Approaching Absolute Zero
Mäkinen and his team developed a system that used radio waves to propel magons—a variety of quasiparticles—into a superfluid made from a light, very stable isotope of helium known as Helium-3, which was chilled to temperatures approaching absolute zero.
Remarkably, the team found that after the radio-wave magnon “injector” was disabled, the magnons self-organized into a time crystal, which remained in motion for several minutes—an unusually long time for such systems—then eventually faded to a level the team said was no longer measurable.
During its weakening phase, the team also observed the time crystal interacting with a mechanical oscillator, in which changes in the device’s amplitude and frequency appeared to influence the time crystal’s interactions with it.
Into the Odd World of Opto-Mechanics
For Mäkinen and the team, the behavior they observed in the time crystal under such conditions was significant, in part because it aligned with phenomena in the field of optomechanics.
“We showed that changes in the time crystal’s frequency are completely analogous to optomechanical phenomena widely known in physics,” Mäkinen said. Such phenomena, Mäkinen says, are the same that scientists rely on for the detection of gravitational waves, for instance.
“By reducing the energy loss and increasing the frequency of that mechanical oscillator, our setup could be optimized to reach down near the border of the quantum realm,” Mäkinen added.
Fundamentally, Mäkinen says that the time crystal’s behavior with relation to optomechanical phenomena offers a promising pathway toward the control of time crystal behavior, which had previously been thought impossible. Such practical control systems for these odd states of matter could lead to applications that include quantum technologies and a range of other uses.
“Time crystals last for orders of magnitude longer than the quantum systems currently used in quantum computing,” Mäkinen said, adding that he and his colleagues hope their research may lead to ways they can be used to improve quantum computers by powering their memory systems.
“They could also be used as frequency combs, which are employed in extremely high-sensitivity measurement devices as frequency references,” Mäkinen added.
The team’s research was detailed in a new paper, “Continuous time crystal coupled to a mechanical mode as a cavity-optomechanics-like platform,” which appeared in Nature Communications.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.