MADRID, 27 Sep. (EUROPA PRESS) –
A new phase of matter, believed to be comprehensible only through quantum physics, it can be studied with much simpler classical methods.
Researchers from the University of Cambridge have used computer models to study possible new phases of matter known as Prethermal Discrete Time Crystals (DTC). The properties of prethermal DTCs were thought to depend on quantum physics: the strange laws that govern particles on a subatomic scale. However, the researchers found that a simpler approach, based on classical physics, can be used to understand these mysterious phenomena.
Understanding these new phases of matter is a step forward toward controlling complex, many-body systems, a long-standing goal with several potential applications, such as complex quantum network simulations. The results are reported in two joint articles in Physical Review Letters y Physical Review B.
When we discover something new, be it a planet, an animal or a disease, we can learn more about it by observing it more and more closely. Simpler theories are tried first, and if they don’t work, more complicated theories or methods are tried.
“This was what we thought was the case for prethermal TTDs,” he said. it’s a statement Andrea Pizzi, PhD candidate at Cambridge Cavendish Laboratory, first author of both articles. “We thought they were fundamentally quantum phenomena, but it turns out that a simpler classical approach allows us to learn more about them. “
DTCs are very complex physical systems and there is still much to learn about their unusual properties. Just as a standard spatial crystal breaks space-translational symmetry because its structure is not the same everywhere in space, DTCs break a clear time-translational symmetry because, when periodically “shaken”, its structure changes with each “push”.
“You can think of it as a parent pushing a child on a swing in a playground.“said Pizzi.” Normally, the parent pushes the child, the child rocks back, and the parent pushes it again. In physics, this is a fairly simple system. But if there were multiple swings on the same playground, and if the children on them were holding hands, the system would become much more complex and much more interesting and less obvious behaviors could emerge. A pre-thermal DTC is one of those behaviors, in which the atoms, acting as oscillations, they only “come back” every second or third push, for instance “.
First predicted in 2012, DTCs have opened up a new field of research and have been studied in various types, including in experiments. Among these, pre-thermal DTCs are relatively simple systems to perform that do not heat up rapidly as would normally be expected, but instead exhibit crystalline behavior over time for a long time: the faster they churn, the longer they survive. However, they were thought to be based on quantum phenomena.
“Developing quantum theories is complicated, and even when you manage it, your simulation capabilities are often very limited, because the computational power required is incredibly large,” said Pizzi.
Now, Pizzi and his co-authors have found that for prethermal DTCs they can avoid using overly complicated quantum approaches and instead use much more affordable classical methods. In this way, researchers can simulate these phenomena in a much more complete way. For example, they can now simulate many more elemental components, gaining access to the scenarios that are most relevant to the experiments, such as in two and three dimensions.
Using a computer simulation, the researchers studied many interacting spins, such as children on swings, under the action of a periodic magnetic field, such as the parent pushing the swing, using classical Hamilton dynamics. The resulting dynamics clearly and neatly showed the properties of pre-thermal DTCs: For a long time, the magnetization of the system oscillates with a longer period than that of the drive.
“It’s amazing how clean this method is,” said Pizzi. “Because it allows us to see larger systems, it makes it very clear what is happening. Unlike when we use quantum methods, we do not have to struggle with this system to study it. We hope that this research will establish classical Hamiltonian dynamics as a suitable approach. for large-scale simulations of complex many-body systems and open new avenues in the study of disequilibrium phenomena, of which pre-thermal DTCs are just one example“.