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The existence of time crystals – a particularly fascinating state of matter – was only confirmed a few years ago, but physicists have already made a fairly significant breakthrough: they have induced and observed an interaction between two time crystals.
In a helium-3 superfluid, two crystals of time have exchanged quasi-particles without disturbing their coherence; an achievement that the researchers say opens up possibilities for emerging fields such as quantum information processing, where consistency is of vital importance.
“Controlling the interaction of two time crystals is a major achievement. Before that, no one had observed two time crystals in the same system, let alone seen them interact, ”said physicist and lead author Samuli Autti of Lancaster University in the UK.
“Controlled interactions are the number one item on the wish list of anyone looking to harness a time crystal for practical applications, such as quantum information processing.”
Time crystals are quite fascinating. They look like normal crystals, but they have an additional and special property.
In regular crystals, atoms are arranged in a fixed three-dimensional grid structure, like the atomic lattice of a diamond or quartz crystal. These repeating networks may differ in their configuration, but they do not move much: they repeat themselves only in space.
In time crystals, atoms behave a little differently. They oscillate, turning first in one direction, then in the other. These oscillations – called “ticking” – are locked on a regular and particular frequency. Thus, where the structure of regular crystals is repeated in space, in the time of crystals it is repeated in space and the time.
Theoretically, time crystals flash at their lowest possible energy state – known as the ground state – and therefore are stable and consistent over long periods of time. This could be exploited, but only if their consistency could be preserved in a controlled interaction.
So Autti and his colleagues in the UK and Finland set up a time crystal play date. First, they cooled helium-3 – a stable isotope of helium with two protons but a single neutron – to a ten-thousandth of a degree from absolute zero, creating a B-phase superfluid, a fluid with zero viscosity at low pressure.
In this medium, the two time crystals appeared as spatially distinct Bose-Einstein condensates of magnon quasiparticles. Magnons are not real particles, but consist of a collective excitation of the spin of electrons – like a wave that propagates through a network of spins.
When the physicists let the two crystals of time touch each other, they swapped magnons – which changed the oscillation to the opposite phase without sacrificing coherence.
The results were consistent with a phenomenon of superconductivity known as the Josephson effect, in which a current flows between two pieces of superconducting material separated by a thin insulator known as the Josephson junction. These structures are one of many to be explored for the construction of qubits, the basic units of information in a quantum computer.
It’s just a very simple interaction, but it opens the door to trying to create and control much more sophisticated interactions.
“Our results demonstrate that time crystals obey the general dynamics of quantum mechanics and provide a basis for further exploring the fundamental properties of these phases, opening avenues for possible applications in developing fields, such as the processing of l ‘quantum information,’ the researchers wrote in their article. .
“Long-lived coherent quantum systems with tunable interactions, such as the robust time crystals studied here, provide a platform for the construction of new quantum devices based on spin-coherent phenomena.
The research was published in Materials from nature.
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