(ORDO NEWS) — Time crystals are a phase of matter in which particles move in an ever-repeating cycle without energy from outside.
The researchers were able to create two time crystals in Aalto University’s low-temperature laboratory and observe their interaction. In the future, time crystals may find applications in devices such as quantum computer memory components.
Professor and Nobel laureate in physics Frank Wilczek, who also recently visited Aalto University to speak at a colloquium of Finland’s leading quantum community, InstituteQ, theorized the existence of time crystals in 2012. Their existence was experimentally confirmed in 2016.
Now, researchers have managed to create and observe the interaction of two time crystals in an experiment conducted in the low-temperature laboratory of Aalto University.
In an ordinary crystal, the atoms or molecules that make it up are organized into a regular crystal structure. Conversely, a time crystal is a group of particles that moves without external energy, always returning to the same state at regular intervals. This means that its regularity is expressed in time and not in space.
Everyone knows that perpetual motion machines are impossible. However, in quantum physics, perpetual motion is itself possible as long as it is not observed.
By loosely binding the particles to their environment, we were able to create up to two time crystals and make them interact,” says Samuli Auti, a researcher at Lancaster University who conducted the Aalto experiment.
Experiments near absolute zero
The researchers brought superfluid helium-3 to one ten-thousandth of a degree from absolute zero, meaning the temperature was exactly -273.15°C. After that, they created two time crystals. After that, they created two time crystals inside the liquid.
Crystals can exist for up to a few minutes, which is a surprisingly long time for a quantum phenomenon. The researchers were able to observe the properties and interactions of the two crystals due to their long existence.
During the experiment, the time crystals formed a two-level quantum system, which is a combination of two independent quantum states capable of occupying both states at the same time.
Researcher Jere Mäkinen from Aalto says that the state of time crystals can be described using oscillations, that is, using sinusoidal waves, the amplitude of which is related to the number of particles, and the frequency describes the energy state of the time crystal.
The time crystals we created differ from each other in that one of them changes its frequency over time, while the other does not. During the experiment, we were able to make their frequencies intersect.
When their frequencies are approximately the same, they interact, and part of the amplitude of each of them passes to the other crystal. In the second experiment, the crystal, which remained regular, was “empty” at the beginning, i.e. its amplitude was zero.
When the frequency of another crystal crossed with the empty one, part of the amplitude passed to it exactly as predicted by the theory describing two-level quantum systems,” Mäkinen explains.
An excellent example of a two-level quantum system is the qubit, a quantum computer equivalent to a bit in traditional computing. If a bit can only have zero or one as its value, then qubits can have both values at the same time.
This is what helps partly explain the exponentially greater processing power of quantum computers compared to conventional computers.
Based on the fact that time crystals formed a two-level quantum system in the experiment, they can potentially be used in devices such as memory components of quantum computers.
Because time crystals can exist at room temperature, they could pave the way for quantum devices that operate at room temperature. Mäkinen says that the study of time crystals is such a new field that all practical applications are purely speculative.
“Apart from quantum computers, time crystals could be useful for things like extremely accurate time measurements.”
The Low Temperature Laboratory is part of the OtaNano research infrastructure available to scientists, research groups and companies in Otaniemi.
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