Buzz
In July 2021, we were all captivated by the news of Google's creation of a time crystal within a quantum computer. Many of us read the stories, filled with claims of defying thermodynamics and possibly paving the way for warp drive technology. But those cool ideas quickly got lost in technical jargon like qubits, eigenstate, and periodicity, sending most of us back to scrolling through Instagram.
It's a fascinating topic, but the science behind it is highly complex and mostly theoretical. In fact, even many scientists can't fully explain what makes a time crystal work. Yet, sometimes when you break down a tricky subject into smaller parts, the whole concept starts to come into focus. Let's try that approach.
10. A Physicist with a Vision and a Catchy Idea
Time crystals were first proposed in 2012 by Nobel laureate Frank Wilczek, a Professor of Physics at MIT. He suggested that these time crystals could exist as a new phase of matter, demonstrating temporal periodicity. Periodicity refers to patterns that repeat over time, like how snowflakes have repeating patterns in 3D space. Wilczek theorized that, with the right condensed matter devices to observe the tiniest of particles, we could detect repeating patterns not just in space, but in time. (If you're confused by this, don't worry—you're right where you're meant to be.)
When liquids freeze, their molecules pull together into a stable arrangement known as the lowest energy state. As the temperature drops, water droplets in the sky become snowflakes, with hydrogen and oxygen molecules bonding to form a hexagonal, crystalline structure, the reasons for which remain partly a mystery. This process is an example of spontaneous symmetry breaking—a term that might seem confusing, since a snowflake's beauty lies in the symmetry of its six arms or branches. So how can symmetry be broken in this case? What's going on?
Water has a kind of symmetry—it appears uniform and feels consistent, with its molecules arranged in a steady manner. But as a snowflake forms, its molecular structure seems driven to break that symmetry by creating six branches extending from a central prism. Wilczek suggested that during the lowest energy state of a quantum-mechanical system, known as time translational symmetry, symmetry could also be broken in the elusive fourth dimension. This would lead to an observable time crystal, similar to how 3D crystals like snowflakes, quartz, and diamonds break spatial translational symmetry.
If all of this sounds like baffling nonsense, you're not alone. Even Wilczek's colleagues struggled to grasp the concept fully. They dismissed his working model, and while his research sparked further debates, they believed he was chasing a very obscure idea. However, the term 'time crystal' had a certain allure. It sounded too fascinating to ignore, quickly making its way into university cafeterias, right alongside phrases like 'black hole,' 'dark matter,' and 'Comic-Con.' This intrigue helped keep Wilczek's theory alive in academic conversations.
A successful campaign always begins with a catchy slogan…
9. Establishing Some Basic Principles
In the first four years following the publication of Wilczek's paper, not only was his model dismissed, but the entire idea of time crystals was deemed outright impossible by researchers at the European Synchrotron Radiation Facility in Grenoble, France, and the University of Tokyo. However, right after these negative assessments, other researchers began searching for potential exceptions to the established rule, hoping to find something that could make the concept viable.
The idea of discrete time crystals spread throughout the realm of quantum physics—the term 'discrete' indicating a unique form of symmetry breaking, differing from the continuous symmetry that we typically observe. Snowflakes provide a good analogy. As they form in the cold, their intricate branches grow with a symmetry of their own, contrasting with the smooth, undisturbed nature of liquid water.
Theorists began to propose that discrete time crystals could potentially break time translational symmetry, especially when exposed to a laser or some other driving force. These particles would acquire their own spin periodicity, repeating in multiples of the periodicity of the driving force. Is it starting to sound confusing? Even physicists find this concept incredibly perplexing, so much so that it makes Newtonian physics feel like a walk in the park. To grasp discrete time crystals, certain foundational principles had to be set up first:
The first rule dictates that the crystal must be robust, meaning it should be stable enough to maintain its state despite external changes within a defined range. Think of how a snowflake remains stable despite minor temperature fluctuations below 0°C (32°F). Similarly, a true time crystal is able to withstand the disruptions of the quantum world.
The second rule requires that a discrete time crystal must resist the thermal energy of the force causing its current quantum state. In simple terms, it must not heat up. The solution to this is known as many-body localization (MBL), which introduces enough disorder to allow destructive interference, where opposing waves cancel each other out. This keeps the crystal from overheating and losing its stability.
With the concept of time crystals thoroughly revised, it was time to take another shot at proving the theory. And many enthusiastic scientists were more than ready to rise to the occasion!
8. A Fresh Approach to Time Crystals
In 2016, two groundbreaking experiments were carried out based on this new understanding. First, Dr. Christopher Monroe of the University of Maryland announced that his team had successfully observed the first instance of a discrete time crystal. Monroe’s group trapped a chain of ytterbium-171 ions within radio-frequency electromagnetic fields, manipulating and monitoring their spin states while bombarding them with lasers.
This manipulation made the ions oscillate in multiples of the driving force’s periodicity—a unique movement, signaling the creation of a discrete time crystal. Imagine a plate of Jell-O wobbling to a rhythm of its own, unaffected by the plate’s movement. The time crystal exhibited a stable and robust subharmonic oscillation, persisting even when disrupted, until the oscillation’s frequency grew too intense, causing it to “melt” at a quantum level.
In the same year, a team from Harvard, under Professor Mikhail Lukin, achieved similar results using a diamond containing nitrogen-vacancy centers (a common impurity). They applied a microwave drive instead of a laser to induce coupled electron spins. Time crystals were also theoretically defined or detected in various other experiments. Some researchers even noted potential signs of time crystals forming naturally in the monoammonium phosphate crystals commonly made in school science projects.
Despite the claims of success in these experiments, skepticism still prevailed. Many scientists felt a more reliable method was needed to confirm the existence of time crystals. To that end, they turned to another cutting-edge area in physics—quantum computing—to help unravel the mystery of time symmetry breaking.
7. What’s So Unique About Time?
Before we can fully grasp time crystals or the fascination they inspire in scientists, we must first understand the elusive nature of the so-called 4th dimension. It’s something we experience daily, yet its intangible essence often perplexes physicists. Time is difficult to comprehend both literally and figuratively. While the numbers on a chalkboard add up just fine, time itself remains a challenge for physicists to fully grasp. Despite the fact we pass through it every moment, time doesn’t behave like the three spatial dimensions. A person can remain still in the 3D world (at least relative to the ground), but try staying still in time—no one has succeeded.
In the 4th century, the philosopher Aristotle mused on time, noting, “Time crumbles things; everything grows old under the power of Time and is forgotten through the lapse of Time.” This early reflection seems to touch on the concept of entropy. Thirteen centuries later, Sir Isaac Newton, physicist and astronomer, proposed that “absolute time” exists only in mathematics, while the time we experience is “relative time,” measured through the movements of objects like the sun or moon.
Albert Einstein later popularized the concept of spacetime with his theory of relativity, combining the three spatial dimensions with time to form a four-dimensional continuum. He also showed how gravity could bend time, a theory proven by the behavior of GPS satellites. At 20,200 kilometers (10,900 nautical miles) above Earth, gravity is weaker by a factor of four. As a result, the clocks in space run 45 microseconds faster each day compared to those on Earth. However, relativity also tells us that moving clocks run slower than stationary ones, which causes the same satellites' clocks to run seven microseconds slower. After adjusting for both effects, the result is that satellite clocks run 38 millionths of a second faster each day. Without computerized compensation, this small discrepancy would cause GPS errors within two minutes.
The math on the blackboard checks out, and we know how to apply it, but how do we actually engage with time? How can we step outside of it to better study its nature? Is it possible to touch or feel time in any way beyond the fleeting “now”? Interestingly, scientists in Stuttgart, Germany, may have captured visual evidence of time on video!
6. Time on Camera
The year 2021 proved to be a milestone in the development of time crystals. In fact, February saw one of them being recorded on video at the Max Planck Institute for Intelligent Systems in Stuttgart. A German-Polish research team bombarded a magnetic strip with a microwave field, resulting in an oscillating, micrometer-sized time crystal formed by magnons arranged in an orderly row. Magnons are quasiparticles, and they oscillated back and forth in perfect synchronization, disappearing and reappearing in a quantum-like dance.
When more magnons were introduced to the crystal, they joined the rhythmic motion, skipping back and forth with exact periodicity between two distinct physical states. The creation of this time crystal was a significant achievement, and the video, captured with an X-ray microscope, is nothing short of remarkable once you realize what you're observing. What made this crystal unique was its relatively large size and its ability to exist at room temperature, instead of in a super-cooled environment. This breakthrough also suggested that time crystals might be far more widespread and durable than previously imagined.
But the Max Planck Society’s contributions to time crystal research didn’t stop there. In 2021, Dr. Roderich Moessner, the director of the Institute for the Physics of Complex Systems, was part of a team of university physicists collaborating with Google to create the first time crystal using a quantum computer. What better setting could there be for constructing such a quantum marvel?
5. What is a Quantum Computer, Exactly?
Many people mistake quantum computing for supercomputing, which is essentially a supercharged mainframe. In classical, or binary computing, information is stored using bits, each representing either a 0 or a 1. Quantum computers, however, use qubits (quantum bits), which can represent 0, 1, or both at the same time in a state called superposition until an outcome is measured. When qubits interact with each other, this phenomenon is known as entanglement. Storing information in superposition allows computations to run exponentially faster as the number of qubits increases.
So, what exactly are qubits made of? Well…you won’t find them at Best Buy. Google's much-hyped Sycamore quantum processor had 54 superconducting transmon qubits (only 53 of which were operational) made of aluminum plates around 100 microns wide, roughly the width of several human hairs. This truly represents information processing on a minuscule scale. But what does the machine itself actually look like?
The Sycamore is a complex setup of lights, filaments, and swarms of twisted wire, all hanging upside down within a cryostat to maintain the ultra-low temperatures required to keep the qubits functioning properly at the quantum level. The whole system is housed inside a casing resembling a giant tin can, with auxiliary controls and equipment filling up an entire room. Needless to say, Google's Sycamore isn’t something that can be mistaken for one of their much more portable Chromebooks.
Not all quantum computers are the same, as they are built by various companies for specific purposes. However, they all have the ability to perform deductions at astonishing speeds. In October 2019, Google declared 'quantum supremacy' over supercomputers when Sycamore solved a random number problem in just 3 minutes and 20 seconds—a task that would have taken IBM's Summit computer around 10,000 years. In response, IBM quickly developed an algorithm that reduced the gap significantly. Even so, the Sycamore still claimed victory. But beware, Google—IBM plans to release a quantum computer with a 1121-qubit Condor chip by 2023. Both companies also have their sights set on processors with 1 million qubits by 2030, which would make the 54-qubit Sycamore (with 1 malfunctioning qubit) seem as outdated as dial-up internet.
But how do these machines actually think? Quantum computers work with probabilities and possibilities, unlike traditional computing, which uses transistors to execute fixed operations. Picture a vast, complex maze connecting point A to point B. Classical computing would eventually find its way to point B through trial and error. On the other hand, quantum computing would consider every possible route at once, then quickly zoom in on the correct solution, saving precious time. Clearly, this is a far more efficient way of problem-solving.
Despite its race against classical computing and its potential for future research, quantum computing hadn’t quite shown its true worth in scientific fields—until discussions surfaced about Google’s Sycamore being used to create a time crystal. Naturally, Google was eager to showcase its quantum achievement once again…
4. Diamond-Encrusted Qubits
Interestingly, the Google team wasn't the first to create a time crystal using qubits and quantum computing. In March 2021, QuTech, a research institute based in the Netherlands, proudly announced their own success by using nuclear spins in a diamond to produce a 'new state of matter.' However, their time crystal lasted only about eight seconds before succumbing to environmental interference. With a perfectly isolated system, though, it could have spun eternally.
QuTech joined forces with Element Six, a provider of artificial diamonds, and UC Berkeley to build their creation with just nine qubits. While working independently from Google's team, both projects were being developed in parallel. This experiment also showcased the diversity and individuality inherent in quantum computers, each with its own distinct design and purpose.
3. What Can We Actually Do with These Quantum Machines?
The downside of time crystals’ perpetual motion is that they’re likely of no practical use, as they reside in their ground state—the lowest possible energy level. It’s like putting dead batteries into a flashlight. And since these crystals are made of quantum particles, they’re certainly not something you’d wear around your neck. They aren’t shiny or attractive, and good luck trying to catch a glimpse of one with today’s technology. Even though theoretically these time crystals could exist forever, let’s not forget that Google’s time crystal lasted a mere eight-tenths of a second.
Let’s dive a little deeper, though, because there’s a huge gap between forever and eight-tenths of a second. The time crystal created by Google was theoretically strong and durable, capable of cycling forever. However, the Sycamore chip itself was flawed, like all quantum devices. Moreover, the crystal was made from qubits, which are highly susceptible to environmental interference, a phenomenon known as decoherence. Researchers are striving to enhance quantum computer efficiency by better isolating the processors. Interestingly, time crystals might hold the key to solving this challenge...
Imagine a quantum computer powered by time crystals—these crystals fluctuate and exist without consuming energy, meaning they don't fall prey to entropy (the inevitable decline into disorder that affects everything else in the universe). As mentioned earlier, qubits, which drive today’s quantum computers, are fragile and prone to decoherence, leading to entropy in their entangled states. But if stable time crystals were used, they could provide entanglement without the destructive effects of entropy. This could usher in the next generation of quantum computing, with extraordinary efficiency and the potential to solve the universe’s deepest mysteries. Think of breakthroughs in chemistry to cure cancer, warp drives to travel to distant stars, and sustainable energy solutions independent of fossil fuels.
Picture a whole new era of computing, and it’s arriving sooner than you think!
2. So…Did We Violate the Laws of Thermodynamics?
After the Google team announced their achievement with time crystals, sensational headlines flooded the news, with many suggesting that they had violated the laws of thermodynamics and unlocked the secret to perpetual motion. These are bold statements that challenge fundamental physics principles. If they were true, it would indeed be a game-changer. However, they are not.
The first and second laws of thermodynamics have been widely accepted since the mid-1800s. The first law states that energy cannot be created or destroyed within a closed system—whether it’s something as small as a molecule or as vast as the entire universe. The second law emphasizes the inevitability of entropy, asserting that energy in a closed system will inevitably spread out, leading to uniform disorder over time.
Both of these laws make the idea of a perpetual motion machine impossible, as any energy expended to power such a device would inevitably transform into heat due to friction. The orbits of the planets in our solar system are often cited as examples of perpetual motion. However, even these orbits are slowly decaying due to an incredibly small amount of energy loss through gravitational waves. (But don’t worry, it’s far more likely that the sun will expand into a red giant and engulf the Earth before this ever becomes a problem!)
Time crystals seem to defy the laws of thermodynamics, much like they defy time-translational symmetry, as they can switch between two states forever without losing energy. However, they don’t actually contradict any established laws of physics. The key here is that the laws of thermodynamics don’t strictly apply at the quantum level. In this case, the system, including the driving force, conserves energy, allowing the time crystal to exist as a “loophole” of sorts. Essentially, time crystals can seemingly suspend the laws of thermodynamics indefinitely, but they don’t actually break them. And that sounds like a clever loophole, doesn’t it?
Loopholes are often quite advantageous for those who know how to make the most of them. Take tax loopholes, for instance, which many rejoice in for saving money, or legal loopholes that keep people out of trouble. So, how might we put this quantum loophole, known as time crystals, to good use?
1. Google’s Step into Temporal-Symmetry Disruption
Google’s achievement in creating a discrete time crystal in the summer of 2021 was far more widely covered than the QuTech experiment—after all, Google is an immense, multinational powerhouse with a color scheme familiar to everyone. But the academic force behind the collaboration was also significant, bringing together scientists from renowned institutions like the Max Planck Institute for Physics of Complex Systems, Stanford University, Oxford University, and, of course, the Google Quantum AI Lab, in partnership with NASA.
This collaboration had hopes beyond merely creating a time crystal. The physicists were also eager to explore what Google’s Sycamore quantum computer could bring to their research into condensed matter physics, which is essentially the study of the electromagnetic forces between atoms in liquids and solids. Google was equally enthusiastic to apply their experimental quantum computer to more than just calculations, as it had previously been used only for the occasional competition with IBM two years before.
The time crystal the team created, composed of 20 qubits, lasted just eight-tenths of a second. However, during this brief moment, the computer observed over a million distinct quantum states of the crystal, even running it forward and backward through time (a fascinating endeavor in itself), ensuring that the crystal showed continuous oscillations in both directions. Yet, while the crystal appeared flawless, its environment was far from ideal. Just like the time crystal from QuTech, it decayed due to environmental interference. Still, during its active state, it met all the required criteria to qualify as a true discrete time crystal!
Naturally, Google garnered most of the media attention for their achievement in creating a new phase of matter. The numerous academics involved in the project were incredibly proud to see their names listed in the article, which was published in the November 30th issue of the prestigious science journal Nature. More importantly, both the Google and QuTech teams demonstrated the nearly boundless potential of using next-generation quantum computers to explore theoretical physics in the near future. These computers have already shown they are capable of far more than just solving equations and navigating mazes.
