The second law of thermodynamics, states that systems naturally tend to settle in a state known as “maximum entropy” reflective of the fact that all things tend to move towards less useful, random states. As time goes on, systems inevitably degenerate into chaos and disorder – that is, entropy. Time crystals, on the other hand, fail to settle in thermal equilibrium. Instead of slowly degenerating towards randomness, they get stuck in two high-energy configurations that they switch between – and this back-and-forth process can go on forever.
Normal crystals have an atomic structure that repeats in space – just like the carbon lattice of a diamond. But, just like a ruby or a diamond, they’re motionless because they’re in equilibrium in their ground state. But time crystals have a structure that repeats in time, not just in space. They’ll sit in one configuration for a while, then flip to another, back and forth and back and forth. While we have a lot of examples of repeated patterns in nature, time crystals are different beasts for two important reasons. For one, they are a stable pattern — the system is in its lowest possible energy state, which means that in principle, they can keep oscillating forever.
This sounds suspiciously like a perpetual-motion machine — hence all the buzz. Usually, when a material is in ground state, also known as the zero-point energy of a system, it means movement should theoretically be impossible, because that would require it to expend energy. But, Nobel-Prize winning theoretical physicist Frank Wilczek, first predicted by back in 2012, time crystals are structures that appear to have movement even at their lowest energy state, known as a ground state.
It wasn’t until 2016 that a group of physicists working at Station Q, a Microsoft research facility at UC Santa Barbara, figured out a way to correct the theoretical problems with Wilczek’s time crystals and provided the stepping stone to actually make them. The group, led by physicist Chetan Nayak, built on prior research from Princeton University, which found that time crystals can spontaneously break a fundamental symmetry called time-translation symmetry to exhibit periodicity over time.
Following the publication of the preprint of Yao’s paper , two teams at the University of Maryland and Harvard managed to experimentally realize a time crystal for the first time, confirming the existence of an entirely new phase of matter. Time crystals — where a web of atoms spin in a perpetual loop — has become the focus of new research by the US military. Time crystals are systems of atoms that maintain a periodic ticking behaviour in the presence of an added electromagnetic pulse. The Defence Advanced Research Projects Agency (DARPA) has admitted its allocated some of its researchers and resources to examine the implications of this breakthrough. Time crystals might one day have technological implications, too. For example, time crystals may form the basis for a nearly perfect memory unit for powerful quantum computers.
Time crystals could be the miracle quantum computing needs
Time crystals, therefore, act more like superconducting materials (such as mercury or lead). Superconductivity is a quantum phenomenon in nature wherein certain materials conduct direct current electricity without any energy loss if they are cooled below a certain temperature. They also expel magnetic fields, according to the U.S. Department of Energy.
Scientists at Aalto University in Finland recently published research indicating “time crystals” may hold the key to creating a quantum computer that doesn’t require near perfect-zero temperatures to operate. Aalto University senior scientist, Vladimir Eltsov says, “Nature has given us a system that wants to be coherent over time. The system spontaneously begins to evolve in time coherently, over long periods of time, even infinitely long.” And that sort of on-demand coherency would go a long way towards making useful quantum computing a reality.
One of the strangest things about qubits is they act differently when observed. Without a certain amount of coherency, any data transmitted, created, or stored in a quantum system could simply vanish the moment we try to look at it. According to the research, the solution might be the generation of time crystals in quantum bits, so that they’ll “want” to be coherent.
Several attempts have been made to create and observe time crystals to date, with varying degrees of success. In July 2021, a team from Delft University of Technology in the Netherlands published a pre-print showing that they had built a time crystal in a diamond processor, although a smaller system than the one claimed by Google n August 2021.
In a new research paper, Google scientists claim to have used a quantum processor for a useful scientific application: to observe a genuine time crystal. Time crystals are also hard to find. But Google’s scientists now rather excitingly say that their results establish a “scalable approach” to study time crystals on current quantum processors.
Google says it has created a time crystal in a quantum computer
For this research—which, notably, has not yet been peer-reviewed for publication in an academic journal—a group of over 100 scientists from around the world collaborated with Google Quantum AI, a joint initiative between Google, NASA, and the nonprofit Universities Space Research Association. Its goal is to expedite research on quantum computing and computer science. In the paper, the scientists describe building a special microscopic rig where a time crystal is surrounded by superconducting qubits.
The quantum computer sits inside a cryostat, which is a temperature-controlled supercooling chamber that keeps all the materials at the right, extremely low temperature for advanced states like superconducting or time crystals (nuclear fusion also relies on cryostats as a way to keep equipment at the right temperature for containing fusion’s extraordinary heat). The search giant’s researchers used a chip with 20 qubits to serve as the time crystal – many more, according to Curt von Keyserlingk, lecturer at the school of physics and astronomy at the University of Birmingham, than has been achieved until now, and than could be achieved with a classical computer.
The scope and control of Google’s experiment means that it is possible to look at time crystals for longer, do detailed sets of measurements, vary the size of the system, and so on. In other words, it is a useful demonstration that could genuinely advance science – and as such, it could be key in showing the central role that quantum simulators will play in enabling discoveries in physics. There are, of course, some caveats. Like all quantum computers, Google’s processor still suffers from decoherence, which can cause a decay in the qubits’ quantum states, and means that time crystals’ oscillations inevitably die out as the environment interferes with the system. The pre-print, however, argues that as the processor becomes more effectively isolated, this issue could be mitigated.