Connecting two “time crystals” in a helium-3 superfluid just one ten-thousandth of a degree above absolute zero could be a big step towards a new type of quantum computer.
Time crystals are bizarre structures of atoms, whose existence was only predicted in 2012, with experimental evidence a few years later. In a normal crystal, such as diamond or salt, the atoms are arranged in a regularly repeating spatial pattern – a lattice or similar framework. And like most materials, when atoms are in their ground state – their lowest possible energy level – they stop shaking.
Time crystals, on the other hand, are made up of atoms that repeat in time rather than space, oscillating back and forth or spinning, even in their ground state. They can maintain this motion perpetually, without requiring energy input or losing energy in the process.
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In doing so, these time crystals can challenge a concept known as entropy. The second law of thermodynamics describes entropy as how any system becomes more disorderly over time. As an example, consider the orbits of the planets around the Sun. For simplicity, we imagine them moving in clockwork order, always returning to the same place at the same time in their respective orbits. In reality, however, things are messy: the gravity other planets, or passing stars, can shoot and shoot at the planets, subtly altering their orbits.
Hence the orbits of the planets are inherently chaotic. A small change to one of them can potentially have a big impact on all of them. The system becomes disordered over time – the entropy of the system increases.
Time crystals can negate the effects of entropy due to a principle of quantum mechanics known as “multiple object localization”. If a force is felt by an atom in the time crystal, it only affects that atom. Therefore, the change is considered localized rather than global (across the whole system). As a result, the system does not become chaotic and allows repeated oscillations to continue, theoretically, in perpetuity.
“Everyone knows perpetual motion machines are impossible,” said Samuli Autti, a researcher and lecturer in physics at Lancaster University in the UK. statement. “However, in quantum physics, perpetual motion is acceptable as long as we keep our eyes closed.”
Autti, who led the research, refers to Heisenberg’s uncertainty principle, which alludes to how, when a quantum system is observed and measured, its quantum wave function collapses. Due to their quantum mechanical nature, Time Crystals can only operate at 100% efficiency when completely isolated from their surroundings. This requirement limits the length of time they can be observed until they completely decay following a wave function collapse.
However, Autti’s team managed to connect two time crystals by cooling an amount of helium-3, an isotope of helium. Helium-3 is special because, when cooled to a fraction above absolute zero (minus 459.67 degrees Fahrenheit or minus 273 degrees Celsius), the isotope becomes a superfluid, which few materials can TO DO. In a superfluid there is no viscosity, so no kinetic energy is lost through friction, thus allowing motions – such as those of atoms in a time crystal – to continue indefinitely.
Autti’s team, working at Aalto University in Finland, then manipulated helium-3 atoms to create two time crystals that interacted with each other. Moreover, they observed this time-crystal pairing for a record duration, about 1000 seconds (nearly 17 minutes), which is equivalent to billions of periods of oscillatory movement or rotation of the atoms, before the function wave of time crystals does not decompose.
“It turns out putting two of them together works wonders,” Autti said.
The results create a promising line of research for the development of a fully functional system. quantum computer. While normal computer bits are binary – 1 or 0, on or off – the processing rate of quantum computers is much faster because they use “qubits”, which can be 1 and 0, on and off at the same time. One way to build a quantum computer would be to link together myriad time crystals, each designed to act like a qubit. Therefore, this first experiment to link two time crystals created the cornerstone of a quantum computer.
Previous experiments have already shown that some time crystals can operate at room temperature, rather than needing to be cooled to near absolute zero, which makes building them even easier. The next task, Autti’s team said, is to demonstrate that logic gate operations, which are functions that allow a computer to process information, can operate between two or more time crystals.
The research was published June 2 in the journal Nature Communication (opens in a new tab).
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