(ORDO NEWS) — Physicists have just taken a surprising step towards quantum devices that will seem like something out of science fiction.
For the first time, isolated groups of particles that behave like strange states of matter known as time crystals have been combined into a single, evolving system that could prove incredibly useful in quantum computing.
After first observing the interaction between two time crystals described in an article two years ago, this is the next step towards the potential use of time crystals for practical purposes such as quantum information processing.
Time crystals, officially discovered and confirmed only a few years ago, in 2016, were once considered physically impossible. They are a phase of matter, very similar to ordinary crystals, but with one additional, special and very specific property.
In ordinary crystals, the atoms are arranged in a fixed three-dimensional lattice structure, similar to the atomic lattice of diamond or quartz. These repeating grids may vary in configuration, but any movement they exhibit is solely due to external factors.
In time crystals, atoms behave somewhat differently. They show patterns of movement over time that cannot be so easily explained by external influences. These oscillations – called “ticks” – are fixed at a regular and specific frequency.
Theoretically, time crystals tick in their lowest possible energy state – known as the ground state – and are therefore stable and coherent over long periods of time.
Thus, if the structure of ordinary crystals is repeated in space, then in time crystals it is repeated in space and time, thus demonstrating the perpetual motion machine of the ground state.
“Everyone knows that perpetual motion machines are impossible,” says physicist and lead author of the study Samuli Auti from Lancaster University in the UK.
“However, in quantum physics, perpetual motion is possible as long as we keep our eyes closed. By sneaking through this gap, we can create time crystals.”
The time crystals the team works with are made up of quasi-particles called magnons. Magnons are not real particles, but are a collective excitation of electron spins, like a wave propagating through a lattice of spins.
Magnons are created when helium-3 – a stable isotope of helium with two protons and one neutron – cools down to one ten-thousandth of a degree from absolute zero. In this case, the so-called B-phase of a superfluid liquid is formed – a liquid with zero viscosity and low pressure.
In this environment, time crystals form as spatially separate Bose-Einstein condensates, each of which consists of a trillion magnon quasi-particles.
A Bose-Einstein condensate is formed from bosons cooled only a fraction above absolute zero (but not to absolute zero, at which the atoms stop moving).
This causes them to descend to their lowest energy state, move extremely slowly, and come close enough to overlap each other, creating a cloud of high density atoms that acts as a single “superatom” or wave of matter.
When the two time crystals were allowed to touch each other, they exchanged magnons. This exchange affected the fluctuations of each of the time crystals, creating a single system with the ability to function in two discrete states.
In quantum physics, objects that can have more than one state exist in a mixture of these states until they have been defined by a precise measurement. Thus, having a time crystal that functions in two states provides a rich choice as the basis for quantum technologies.
Time crystals are still far from being used as qubits, since a significant number of problems must be solved first. But the details are starting to fall into place.
Earlier this year, another group of physicists announced that they had successfully created temporary crystals at room temperature that do not need to be isolated from the environment.
More complex interactions between time crystals and fine control over them will require further development, as will the observation of interacting time crystals without the need for cooled superfluids. But scientists are optimistic.
“It turns out that if you put two of these crystals together, they work great, even if the time crystals shouldn’t exist at all,” says Auti. “And we already know they exist at room temperature.”
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