The long-term promise of reliable quantum computing is hard to overstate. Its potential to cure disease, create much-needed material breakthroughs, and even solve big problems like climate change is not technological bluster, it’s a real possibility. Time crystals are an entirely new form of matter in which particles move forever and don’t lose energy.
A team at Oxford University has successfully linked two quantum processors together using optical fibre and quantum teleportation. The breakthrough could help solve the “scalability problem” of quantum computing, which is the difficulty of increasing the number of qubits in a system without increasing noise.
This distributed architecture resembles the general structure of classical supercomputers, but thanks to qubits, the system can solve problems in a matter of hours that would take conventional supercomputers years to solve.
The long-term promise of reliable quantum computing is hard to overstate. Its potential to cure diseases, create much-needed material breakthroughs, and even solve big problems like climate change is not technological bluster, it’s a real possibility. That promise is why companies and governments are investing billions each year to unlock the potential of qubit-based computing. But significant obstacles remain between now and that distant dream, and scalability remains enemy number one.
Simply put, qubits are incredibly sensitive to their environment and require extremely precise control. These problems only increase as more qubits are added to the system, and eventually, quantum computing’s precision breakdowns — also known as “noise” — eventually lead to cascading errors. That’s why the current era of quantum computing is commonly known as the “noisy intermediate-scale quantum (NISQ) era.” These quantum processors contain a maximum of 1,000 qubits and are not fault-tolerant enough to unlock the full potential of quantum computing.
Alex Greulich/TU Dortmund
Of course, scientists have several methods for making quantum computers less error-prone, including robust error correction and fault-tolerant computing. And recently, researchers at Oxford University made a major breakthrough in increasing the number of qubits in a quantum system. The idea is simple: instead of packing more qubits into a single system, what if smaller quantum processors could form a distributed network? This could theoretically allow scientists to scale the number of qubits while keeping noise levels low.
In a new paper published in the journal Nature, the scientists detail how they connected modules containing only a small number of trapped ion qubits using optical fibers to transmit photons. These photonic links then allowed the qubits to become entangled across the optical fibers, enabling quantum logic to be performed via quantum teleportation.
“Previous demonstrations of quantum teleportation have focused on transferring quantum states between physically separated systems,” said Dougal Main, lead author of the study from the University of Oxford, in a press release. “In our study, we use quantum teleportation to create interactions between these distant systems. By carefully tuning these interactions, we can perform quantum logic gates — the fundamental operations of quantum computing — between qubits housed in separate quantum computers. This breakthrough allows us to effectively ‘link’ separate quantum processors into a single, fully connected quantum computer.”
To test this new system, the team ran the so-called Grover search algorithm, first described by Indian-American computer scientist Lov Grover in 1996. This search looks for a specific element in a large unstructured data set using superposition and entanglement in parallel. The search algorithm also exhibits quadratic speedup, meaning the quantum computer can solve the problem with the square root of the input rather than just a linear increase. The authors report that the system achieved a 71 percent success rate.
While successfully managing a distributed system is a major step forward for quantum computing, the team reiterates that the engineering challenges remain daunting. However, connecting quantum processors into a distributed network using quantum teleportation offers a small glimmer of light at the end of the long, dark tunnel of quantum computing development.
“Scaling quantum computers remains a challenging technical challenge that will likely require new physical knowledge as well as intensive engineering efforts in the coming years,” said David Lucas, the study’s principal investigator from the University of Oxford, in a press release. “Our experiment shows that distributed quantum information processing is possible using current technology.”
For quantum computers to reach their full potential, they need to be more robust — able to reduce errors and avoid decoherence. As described in a new study by Chinese and American scientists, the team successfully introduced the inherent stability of a topological time crystal into a quantum computer, which then showed signs of improved reliability.
While more widespread adoption in quantum computers is still a long way off, this study shows that the quantum time crystal system holds great promise for the future of quantum computing.
Quantum computing—like fusion or room-temperature superconductors—always seems far from having a profound impact on human life. And while this slow progress may seem frustrating, there’s a reason why these concepts continue to be relentlessly pursued around the world. A room-temperature superconductor will revolutionize the electric grid, fusion will bring the sun’s energy to Earth, and quantum computing can solve problems (even extremely complex ones like climate change) that we’ll never be able to solve with classical computing alone.
But, as with fusion and superconductors, there are several challenges to this quantum computing dream. Chief among them is a lack of robustness. Because of the complex science behind quantum computers, these machines are incredibly susceptible to noise and errors, which eventually lead to decoherence—the end of the quantum superposition state that makes qubits so useful.
A time crystal is an exotic state of matter that combines the rigidity of a regular crystal with a regular rhythm in time. Popular Mechanics Magazine
So, to improve resilience, a team of scientists from the US and China exploited the inherent stability of another quantum system known as a time crystal. By effectively turning a quantum computer into a time crystal, the researchers were able to create topological time crystals that could last longer than expected. The results were published in the journal Nature Communications.
Aside from being a great name for a kind of plot device in a B-movie sci-fi movie, time crystals also seem to defy our typical understanding of physics. First discovered by physicist Frank Wilczek in 2012 (a discovery that earned him a Nobel Prize), time crystals behave like standard crystal structures, but in time. Where a normal crystal (like a diamond) repeats itself in its atomic structure, a time crystal repeats itself not in the physical dimension, but in the time dimension. This is such a concept because time crystals seem to defy the famous second law of thermodynamics.
This research focuses on topological time crystals, the behavior of a topological time crystal is determined by its overall structure, not just a single atom or interaction. As ZME Science describes, if regular time crystals are a thread in a web, then a topological time crystal is the entire web, and even changing one thread can affect the entire web. This “web” of connections is a feature, not a flaw, as it makes the topological crystal more resistant to interference—something quantum computers could certainly exploit.
In this experiment, the scientists essentially engineered this behavior into a quantum computer, creating a precision that surpassed previous quantum experiments. And while this all happened in a pre-thermal regime, it’s still a big step toward potentially creating a more stable quantum computer that could finally unlock that future that always seemed like a decade away, according to ZME Science.
In early 2017, scientists began studying a new kind of matter: time crystals. Crystals are structures in which the pattern of atoms or molecules repeats itself in space. Two teams of researchers have discovered that repeating patterns in crystals can also exist in time. These “time crystals,” detailed in a new paper in Physical Review Letter, are an entirely new kind of matter that can never reach equilibrium.
To create the time crystals, researchers at the University of Maryland strung together 10 ytterbium atoms and hit them repeatedly with two lasers to keep them out of equilibrium. Although the atoms arranged themselves in a certain order, they failed to achieve equilibrium, meaning the crystals are constantly in motion, even though they contain no energy. Almost all of physics is based on the study of matter in equilibrium, so the ability to create these nonequilibrium crystals has huge implications for the future of physics.
Physicists at the University of Maryland have created the first crystal using a one-dimensional chain of ytterbium ions. Popular Mechanics Magazine
“It’s a new phase of matter, period, but it’s also really cool because it’s one of the first examples of non-equilibrium matter,” lead researcher Norman Yao of the University of California, Berkeley, told EurekaAlert!
The idea of time crystals – a form of matter that appears to move even in its energy-free ground state – was first proposed by Nobel Prize-winning theoretical physicist Frank Wilczek in 2012. Normally, if matter is in its ground state, motion should be impossible because it contains no energy.
Researchers say that time crystals are like jelly. When you tap the jelly, it shakes. The only difference is that crystals shake without using energy, without being touched. By definition, time crystals can never stop shaking, no matter how little energy they contain.
In 2020, for the first time in history, scientists recorded the interaction of time crystals. Time crystals are an entirely new form of matter in which particles move forever and do not lose energy. Interacting time crystals passed magnons back and forth and remained stable.
For the first time, scientists have observed the interactions of a rare and mysterious form of matter called time crystals. The crystals look like “ordinary” crystals at first glance, but they have a connection to time that both intrigues and puzzles scientists because of their unpredictability. Now, experts say they could find applications in quantum computing.
It wasn’t until the 2010s that scientists began to theorize about the existence of time crystals, making it a state of matter equivalent to so-called ruby chocolate. By 2015, the researchers had mapped out ways in which time crystals, collectively called “a nonequilibrium form of matter,” could exist: “The team investigated what happens when certain isolated quantum systems, made up of a mixture of interacting particles, are repeatedly hit with a laser. Contrary to conventional physics, which said that chaos would break out as soon as the systems heated up, the Princeton team’s calculations showed that under certain conditions, the particles would stick together, forming a phase of matter with previously unseen properties.”
Now, the researchers say, they have smashed two time crystals together to see what happens next. “Our results show that time crystals obey the general dynamics of quantum mechanics and offer a basis for further study of the fundamental properties of these phases, opening the way for possible applications in emerging fields such as quantum information processing,” they explain in a new paper.
Laboratory. Aalto University/Mikko Raskinen
In their experiments, they placed two time crystals in superfluid and mixed magnons between them. Magnons are a magnetic quasiparticle that in this case led to “antiphase oscillations,” while the crystals themselves remained phase-stable. What’s cool (and, literally, supercool) is how matter operates in predictable quantum-mechanical ways, despite the central quality of wild patterns of oscillation over time.
“No one has ever observed two time crystals in the same system before, let alone seen them interact,” lead author Samuli Auti of Lancaster University said in a statement. “Controlled interactions are the number one wish list item for anyone who wants to use a time crystal for practical applications such as quantum information processing.”
Without this key discovery, people would probably never have been able to even entertain the idea that a time crystal could be part of an engineered system.
What is this strange oscillation that distinguishes these crystals? There is an internal movement that seems to violate one of the fundamental laws of physics, which is that moving particles keep moving and never seem to lose energy. Where does the initial energy come from, and why does it never dissipate? In a way, studying how crystals interact makes the question more mysterious, because it narrows down some of the parameters. Crystals behave normally in these certain other ways, and this means that whatever the source of the energy or phenomenon is, it remains the same.
In early 2024, scientists built a time crystal that lasted 40 minutes. Time crystals are a relatively new field of physics that exhibit surprising properties: they arrange themselves in repeating patterns, like crystals, but in time rather than space.
Although scientists have created many discrete time crystals, only one group has succeeded in creating a continuous time crystal, and only for a few milliseconds.
Now scientists from the Technical University of Dortmund have created a model that worked 10 million times longer – about 40 minutes.
While the atoms of ordinary, everyday crystals are arranged in a repeating pattern in space, time crystals are additionally arranged in a repeating pattern in time — essentially, they are crystals that exist in a dimension beyond our typical three-dimensional perception. “It’s a way of having your cake and eating it, too,” said US Nobel laureate Frank Wilczek, who first conceived of time crystals in 2012.
Time crystals are created the same way many things are in advanced physics: using supercooled atoms (aka Bose-Einstein condensates) and lasers. While this exciting new phase of matter could have revolutionary applications in the world of quantum computing, they tend not to last long. In 2022, for example, scientists at the University of Hamburg observed a continuous time crystal, but it only lasted a few milliseconds.
Now, researchers at the Technical University of Dortmund have created a continuous time crystal that lasted 10 million times longer, about 40 minutes. In Wilczek’s own words, that’s a long time.
To create this time crystal, TU Dortmund physicist Alex Greulich and his team created a crystal of indium gallium arsenide doped with silicon (aka a semiconductor). In this crystal, nuclear spins “act as a reservoir for the time crystal,” according to a university press statement. After cooling to 6 Kelvin and exposing it to a laser, a nuclear spin is formed by the laser interacting with the loosely held electrons.
The polarization of the nuclear spin then creates oscillations that resemble a time crystal. And amazingly, these repeating oscillations lasted for as long as 40 minutes — an order of magnitude longer than any continuous time crystal that had ever existed. The results of this study were published in late January 2024 in the journal Nature.
While 40 minutes is an achievement, it may be just the beginning of how long such time crystals can last. According to ScienceAlert, this crystal showed no signs of decay after 40 minutes, meaning future time crystals could last for hours or longer.
Could these crystals help us travel through time? To get a feel for time crystals, think of snowflakes or rubies — crystals that tantalizingly distort spatial symmetry. Unlike perfectly symmetrical empty space, these spatial crystals have spots that look different from other spots, like their edges. In the same way, a time crystal breaks time symmetry: its atoms like to be in different points in space at different moments in time, changing directions as if they were being flipped by a pulsating force, writes Popular Mechanics.
Moreover, time crystals can move without absorbing energy because they are made of trapped ions – mixtures of electric or magnetic fields that can trap charged particles, usually in a system isolated from the outside environment, with the ability to spin relentlessly, even at their lowest energy point (the so-called ground state).
Vladimir Yeltsov, an applied physicist at Aalto University in Finland who, together with Professor Grigory Volovik and PhD student Samuli Auti, turned a time quasicrystal into a full-fledged and superfluid time crystal in May 2018, admires the virtues of time crystals – even if he doesn’t (yet) believe in their ability to turn us all into budding Doc Browns.
Professor Grigory Volovik (left) and Vladimir Yeltsov (right) discuss time crystals. They have just measured the time crystal signal (visible on the computer screen behind Yeltsov’s hand). Popular Mechanics Magazine
Instead, Elstow prefers to think about how time crystals could advance us technologically. For example, time crystals could help us build highly sensitive magnetic field detectors or quantum computer components. And such is Elstow’s faith in these fascinating structures that he believes they could become our allies in solving the most theoretical and high-brow problems related to the fundamental laws that govern the universe.
In 2012, MIT theoretical physicist and Nobel laureate Frank Wilczek first proposed that the periodicity (the property of appearing in space at ordered intervals) of crystals was also a matter of timing; Wilczek imagined the system, in its lowest energy state, being able to freeze into space like a normal crystal. In a heated moment, however, Patrick Bruno of the European Synchrotron Radiation Facility in Grenoble, France, and then moments later Haruki Watanabe of the University of California, Berkeley, and Masaki Oshikawa of the University of Tokyo, dismissed Wilczek’s proposal as unfeasible.
“Where on Earth can a system in its ground state find the energy to produce periodic motion in the first place?” they barked. Only in a system that has been disturbed from equilibrium—its steady state—by some driving force can the periodic behavior of a time crystal be achieved, Watanabe and Oshikawa said. That’s it. The scientific community quickly revived the notion of “Floquet systems,” or quantum systems in which some type of driving force imbues the system with periodicity (originally understood and mathematically calculated in the 19th century by the mathematician Gaston Floquet).
In 2015, theoretical physicist Shivaji Sondhi and his colleagues at Princeton University published a paper outlining the theoretical basis for how time crystals might actually exist. “At that point, we weren’t thinking about time crystals specifically, but rather about nonequilibrium states of matter,” says Vedika Khemani, then a member of the pioneering Princeton team and now a condensed-matter physicist at Stanford University. The group was investigating what happens when certain isolated quantum systems, made up of a mix of interacting particles, are repeatedly hit with a laser.
Consider a pendulum. A normal pendulum, one that is not powered by a battery or any other generator, will eventually succumb to friction and slow down. Even in an “idealized” pendulum placed in a frictionless environment—a vacuum—the interactions between the many particles that make up the pendulum will create internal stresses and force the pendulum back into inertia. An even more idealized pendulum made of only one particle would be able to swing back and forth forever, but it would not be a unique time crystal. By contrast, the Princeton team’s pendulum was one in which many particles could continue to pulsate forever without requiring a constant supply of energy. It was an entirely new state of matter.
Soon, two groups of experimenters began trying to build time crystals in the lab. The first, at Harvard University (where Hemani was also a member), experimented with creating an artificial lattice in synthetic diamond. The second, at the University of Maryland, used a chain of charged particles called “ytterbium ions.”
Prestigious universities like Princeton, Harvard, and the University of California at Berkeley aren’t the only institutions that have dove headfirst into time crystal research. Even the U.S. Army has devoted significant resources to uncovering the mysterious qualities of these conceptually astonishing structures.
So if time crystal research shows no signs of depletion, perhaps they will allow time travel after all?
“No,” Khemani says bluntly. “It’s a completely new phase of matter that’s really special, really exotic. But that’s it.” And her view is shared by every scientist we interviewed, including Steven Haller, a physicist at Fordham University who experiments with crystals in optical systems.
“Time crystals could instead be used as quantum memories,” says Holler. Quantum communication, the transfer of information using quantum bits, could give us a very secure way to send information from one place to another, which could be useful for, say, banking or national security. It seems that the extreme durability of time crystals in circumstances that are impossible elsewhere could also hold the secret to achieving consistency in quantum computing, echoes Yeltsov.
However, we will have to wait at least five years before quantum communication systems hit the market and start to penetrate our commercial systems, says Holler. Meanwhile, scientists like Hemani remain cautious about the whole conversation around quantum communication.
Still, is it really so wrong – and beyond the realm of scientific possibility – that we still want to bend time in ways other than time crystals?
Here’s the good news: “Time travel cannot be ruled out in principle,” says Yeltsov.
Now here’s the slightly disappointing news: “But to understand this would require enormous energy densities that we cannot obtain in the laboratory now or in the foreseeable future.”
Consider the Large Hadron Collider (LHC) at CERN, the European Organization for Nuclear Research. The LHC, the world’s largest and most powerful particle accelerator, weighs more than 38,000 tons, runs 27 kilometers (17 miles) in an underground tunnel, has its particles guided by titanic superconducting magnets spinning madly around it at 11,000 revolutions per second, and costs about $4.8 billion. That’s really, really big — and we still need orders of magnitude more to even begin to look at time travel, says Holler. We’re just not ready.
“It’s completely unfeasible with current technology,” says Kurt von Keyserlingk, a theoretical physicist at the University of Birmingham who did additional theoretical work with Khemani and Szondi on time crystals in 2016. “But that doesn’t mean it’s impossible,” he quickly adds, urging us to look at the work of physicist Kip S. Thorne.
In 2017, Thorne was awarded the Nobel Prize in Physics, along with Rainer Weiss and Barry K. Barish, for the first detection of a gravitational wave. Thorne is best known in the cutthroat world of physics as a creator of science fiction-friendly ideas. It was he who advised cosmologist and author Carl Sagan to use a hypothetical traversable wormhole connecting two time periods to transport Jodie Foster across the universe in Contact, the 1997 film based on Sagan’s 1985 novel. He also helped create the black hole for Interstellar and has said that wormholes could be used for space and time travel.
A Fordham University student (Jeda Mackayla Mendoza) adjusts a laser in a lab. “There are no crystals (of time or anything) in this picture, and we only use crystals as a means to change the wavelength of the light source, but lasers are always cold,” says Steven Holler, a physicist at Fordham. Popular Mechanics
Thorne has offered explanations for several logical puzzles about time travel, including the paradox of going back in time through a wormhole and accidentally killing your grandfather, thereby killing yourself. (How can you exist if your father doesn’t exist, since the sperm responsible for his conception was destroyed by… you?) In 1991, Thorne did some math and found that such paradoxes can’t arise, but are instead replaced by an infinite number of other potential outcomes. (You can go back in time and mess around with your grandfather all you want, but there’s no way you could kill him, or you wouldn’t exist to kill him in the first place.)
Then there is the many-worlds hypothesis, which could resolve some of the implications of going back in time and changing the future. This hypothesis suggests that we live in a near-infinity of universes that have the same physical laws and values, but exist in different states and are organized in such a way that no information can flow between them. In essence, with every decision we make, the universe splits into multiple realities, and we are completely unaware of the alternative scenarios that exact copies of ourselves are experiencing in other universes.
“Solving the hardest problems in physics requires abandoning a lot of our preconceptions… Time travel, according to the multiverse theory, would take us to one of these other universes, so it wouldn’t necessarily be a straight linear path back and forth for us, but a transition between universes,” says Holler. “I don’t fully believe that, but there are a lot of smart people working on it, and they seem to think that it’s very, very feasible,” he continues.
But the incredibly attractive multiverse theory lacks the support of reliable calculations, says von Keyserlingk. For him, the problem with the many-worlds interpretation and time travel is not that they are necessarily fiction, but that we may currently lack the mathematical tools and even the philosophical ideas to discuss them. They are at the very theoretical end of physics, he says: things we can only speculate about, while science is at best just “informed guesswork.”
“Sometimes it can happen that nature poses questions that no one has solved before,” says von Keyserlingk. “One of the problems is that we have a fairly fixed idea of what space and time are. Solving the hardest problems in physics requires abandoning many of our preconceived notions.”
