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We all have in mind what a crystal is. At school we learned that, from grains of sugar to diamonds, these materials share a homogeneous and orderly arrangement of their atoms, giving shape to a pattern that is repeated throughout space, giving rise to their beautiful and regular shapes. During a class at the Massachusetts Institute of Technology (MIT) where he is a professor, the Nobel Prize in Physics Frank Wilczek an idea occurs to him: what if there were some ‘time crystals‘ whose structure, instead of repeating itself in space, repeated itself in time?
This ‘exotic’ hypothesis raised in 2012 generated a strong debate in the scientific community for years. If possible, these types of crystals should be able to preserve their stability but, at the same time, also change their crystal structure periodically; that is, if we observed them at different times, we should perceive that its structure (in space) is not always the samebeing in a state of perpetual motioneven in a state of minimum energy or ground state.
All this directly undermines the laws of thermodynamics. AND these crystals would be neither solid nor liquid nor gas. not even plasma -ionized gas-. They would be another different state of matter.
After fierce debates in which Wilczek was branded as almost crazy, in 2016 a team finally managed to show that it was theoretically possible to create time crystals, a feat that was achieved just a year later. Since then, this field of physics has become a very promising field that might revolutionize everything from quantum technology to telecommunications, through mining or the very understanding of the universe.
However, there is a problem: these crystals only appear in very particular conditions. Specifically, scientists often use Bose-Einstein condensates of magnon quasiparticles, a state of matter that is created when particles, called bosons, cool to near absolute zero (-273.15 degrees Celsius, or -460 degrees Fahrenheit). Fahrenheit). This requires very sophisticated equipment and, of course, cannot leave the laboratories and vacuum chambers, since the interaction with the external environment makes its creation impossible.
Until now. A team from the University of California Riverside has managed to create optical time crystals that can be generated at room temperature, as they explain in a study in the journal ‘
Nature Communications‘. To do this, they took a tiny micro-resonator -a disk made of magnesium fluoride glass of only one millimeter in diameter that enters into resonance when receiving waves of certain frequencies-. They then bombarded this optical micro-resonator with beams from two lasers.
The subharmonic peaks
The subharmonic peaks (solitones), or frequency tones between the two laser beams, which indicated the breaking of time symmetry and thus time crystals had been created. The system creates a rotating lattice trap for optical solitons in which their periodicity or structure in time is then displayed.
To maintain the integrity of the system at room temperature, the team used self-injection lock, a technique that ensures the laser output maintains a certain optical frequency. This means that the system might be taken out of the laboratory and used for field applications, specifically for time measurements, integrated into quantum computers, or studying the state itself.
“When your experimental system has an energy exchange with its surroundings, dissipation and noise work hand in hand to destroy the temporal order,” he explains.
it’s a statement Hossein Taheri, Marlan and Rosemary Bourns professor of electrical and computer engineering at UC Riverside and lead author of the study. “On our photonics platform, the system strikes a balance between gain and loss to create and preserve time crystals.”
