In 2012, physicist Frank Wilchek of the Massachusetts Institute of Technology noted that the laws of physics also have temporal symmetry. This means that any experiment repeated later must give the same result. Wilczek drew an analogy with normal crystals, but in the measurement of time, calling this spontaneous time-breaking symmetry a time crystal. A few years later, physicists were finally able to build it.
“Time crystals span a part of the interface between the two worlds. Perhaps we can learn how to remove the interface by studying time crystals in detail,” said Samuli Autti, the lead scientist on the project from Lancaster University in the UK.
In a new study, Autty and his team used “magnons” to create their time crystal. Magnons are quasiparticles that arise in the collective state of a group of atoms. In this case, a group of physicists took helium-3 (a helium atom with two protons, but only one neutron) and cooled it to within a ten-thousandth of a degree above absolute zero. At this temperature, helium-3 turned into a Bose-Einstein condensate, where all atoms have a common quantum state and work in harmony with each other. In this condensate, all the spins of the electrons in helium-3 are connected and work together, generating waves of magnetic energy – magnons. These waves splashed endlessly here and there, turning into a crystal of time.
Autty’s team took two groups of magnons, each working as a separate time crystal, and brought them close enough that they could influence each other. The combined system of magnons acted as one time crystal with two different states.
The purpose of this experiment is to create a stable system of time crystals that could be used for quantum computing. In classical computer systems, the basic unit of information is a bit, which can take a state of 0 or 1, while in quantum computing, each “qubit” can be in more than one place at a time, which allows you to perform many more calculations.
“This could mean that time crystals can be used as a building block for quantum devices that work also outside the laboratory. In such a venture the two-level system we have now created would be a basic building block,” Autti said.
This work is now very far from a working quantum computer, but opens up interesting areas of research. In fact, physicists have created a system of two connected time crystals, which are strange quantum systems stuck in an infinite loop to which the usual laws of thermodynamics do not apply. If scientists can manipulate a two-crystal time system without destroying its quantum states, they could potentially build larger time crystal systems that would be real computing devices.
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