Time crystals have been all the rage in the pop-science world for a few years now, but understanding them isn’t all that easy. Although these new concepts are important for the future of human technology, the average person isn’t well versed in quantum mechanics or theoretical physics. With these ideas and technologies being so potentially impactful, we have created this guide to help anyone understand what time crystals are and why they are important. Let’s take a look at the crystals that could “break modern physics” and see why they even matter!

What is a Time Crystal?

A time crystal is a system of particles arranged in a structure where the lowest energy state is one of constant oscillation.

If you read that and aren’t any closer to understanding what a time crystal is, that’s totally fine! Our goal today is to get you caught up on what a time crystal is, even if you don’t have a background in science. Keeping that definition in mind, let’s take a deeper look at what is being said. In order to understand a time crystal, we need to understand a little about crystals themselves.

Crystals in Three Dimensions

We encounter crystals in our daily life all the time. Salt, sugar, and snowflakes are all examples of matter arranged into a crystalline structure. Crystals that we can hold and interact with within our daily life are simply atoms arranged in a repeating pattern. This repeating pattern of atoms exists in three dimensions, or said another way; three-dimensional crystals are simply patterns of atoms arranged in a repeating structure.

Take sucrose, for example. Sucrose, commonly known as sugar, is at its basic level, a molecule made up of atoms smooshed together. If you were to take a bunch of sugar molecules and arrange them in a repeating pattern that connects them to one another, you would have just made a small sugar crystal! Get enough of them, and you can sweeten your coffee in the morning.

What makes these crystals three-dimensional is that they can move in three dimensions. These dimensions are up/down, left/right, and forward/backward. Essentially, an X, Y, and Z-axis. Remember geometry and algebra? All that graphing is starting to come in handy now.

Now that we understand three-dimensional crystals let’s move on to four-dimensional crystals.

Crystals in Four Dimensions

If you were going to locate an object on earth, you could find it if you were given coordinates on an X, Y, and Z-axis. For example, a coffee cup on my desk is three feet up in the air, two feet to the left of me, and two feet in front of me. But what about the fourth dimension? In order to truly find the coffee cup, you would also have to ask when it was.

A four-dimensional crystal has the same properties as a three-dimensional crystal, just with an added dimension of time. Where a three-dimensional crystal repeats its pattern in the “physical” realm, a four-dimensional crystal has a pattern that repeats across three space dimensions and a one-time dimension. This combination of dimensions is known as “spacetime.”

Crystals are repeating structures of atoms, whereas time crystals are repeating systems of atoms that cycle in a constant pattern over time, not just space.

Oscillation

So, we know what a crystal is, and we know that time crystals repeat in 4D space known as spacetime. The final piece to time crystals is their oscillation. The oscillation of the atoms in the time crystal is the thing that is actually “repeating.”

Oscillation is a regular or repetitive variation with a constant value. An easy way to imagine oscillation is with a metronome. A metronome oscillates back and forth between two positions, and in a perfect world, it is always constant.

One of the important properties that time crystals have is their oscillation. When a set of atoms gets a nudge of energy, the atoms “flip” direction, similar to a crowd doing the wave at a football stadium (if the people were atoms). Every few seconds, the wave comes back around, and the atoms (people) change their state (from sitting to standing up and waving their arms).

What is important about time crystals is that their most basic state is one of oscillation. Essentially, once a time crystal begins to oscillate, it does so as a closed system and is in total equilibrium. To continue with our “wave” metaphor, once one person starts the wave, it never stops. The people in the crowd constantly flip states when they are nudged by the person next to them. This forms a loop where the people (atoms) are in a stable structure that repeats over time.

Conventional crystals are stable patterns of atoms that repeat to form a structure. Time crystals are groups of atoms that stably oscillate in a repetitive and constant motion.

Revisiting the Definition of Time Crystals

A time crystal is a system of particles arranged in a structure where the lowest energy state is one of constant oscillation.

Looking at this definition again, it should make a bit more sense. Time crystals borrow their name from the stable structures of repeating atoms that we call crystals. Regular crystals repeat their structure; time crystals repeat their motion pattern.

When Were Time Crystals Discovered and Who Discovered Them?

The concept of time crystals was first theorized by Frank Wilczek, a Nobel laureate and theoretical physicist, in 2012. The idea was then followed up and expanded upon by Xiang Zhang in 2013 when his team proposed the idea of a constantly rotating ring of oscillating ions (atoms with an electric charge).

Frank Wilczek first applied the term time crystals with the idea that a type of matter could exhibit a fundamental oscillation over time, and Xiang Zhang practicalized it with his theory of charged atoms in a ring. Although Frank Wilczek popularized the term, it was originally used by Arthur Winfreein as a way to describe biological systems that repeat.

What Can Time Crystals Be Used For?

The most promising use for time crystals is likely in quantum computing. Currently, quantum computers build memory using electron spins, with various spins representing either a 1 or a 0 in binary. A problem, however, is that electron spin isn’t all that stable, and outside forces like heat or magnetism can easily disrupt the spin of the elections. The subsequent data would then be rendered inaccurate. Time crystals, however, provide a stable, repeating system that can be nudged into certain patterns with lasers. Once we can write or rewrite the oscillation of these stable systems, the resulting system makes for a superior form of data storage.

Do Time Crystals Violate Thermodynamics?

For anyone with a bit more of an advanced understanding of physics, there may appear to be a glaring problem with time crystals. The problem has to do with thermodynamics. The Second Law of Thermodynamics states that the total energy of a system can never decrease.

An example of this can be seen in a bouncing ball. After dropping the ball from a certain height, each bounce of the ball will continue to decrease. There are various factors that slowly decrease the energy system of the ball and the surface it is bouncing on. Air resistance and sound are two easy factors to point out. Each time the ball moves, the air around it is pushed away. The energy to move the air comes from the ball’s inertia itself, reducing the ball’s potential energy as it reaches the peak of its bounce again. Additionally, the ball’s sound on the table is essentially a wave of air that our ears can pick up. In other words, the sound is energy loss.

Time crystals are systems that possess “motion without energy.” Crucially, their motion doesn’t produce any heat, allowing the system to exist perpetually.

So time-translation symmetry can be broken indefinitely within the time crystal system, but this perpetually rotating object doesn’t heat up, so the second law of thermodynamics remains intact – a crucial stipulation for a time crystal to exist within the laws of physics. 

Science Alert

Do Time Crystals Exist, or are they Created?

Although we haven’t observed time crystals occurring naturally, some recent experiments have been able to produce them in a lab. Recently, labs and research groups all over the world have been pushing to innovate within this field, as it has many potential uses within the quantum technology sphere.

Two teams have created time crystals in a lab setting. Chris Monroe and his team from the University of Maryland created a chain of ytterbium ions and shot them with a laser. A different team from Harvard was able to blast nitrogen impurities within diamonds with microwaves. Although both teams approached from very different angles, both were able to achieve spin systems that oscillated at a period faster than the laser they were shot with.

What is a ‘Time Crystal’ and Why Does it Matter? FAQs (Frequently Asked Questions) 

What is the purpose of a time crystal?

Time crystals don’t inherently serve a purpose, but they could potentially be used for memory storage in the age of quantum computing.

Do time crystals exist in nature?

Although we haven’t observed time crystals in nature yet, they have been created in a lab (according to Norman Yao’s definition of a time crystal).

Can you hold a time crystal?

Time crystals don’t exist as we understand them in physical space, meaning we can’t hold them in our hands like a regular crystal. Time crystals are systems, not objects.

What is a time crystal in layman's terms?

In layman’s terms, time crystals are systems of moving matter where that cycle through a pattern that is resistant to entropy, essentially creating a new phase of matter.

Can time crystals create infinite energy?

Time crystals cannot create infinite energy because they abide by the Second Law of Thermodynamics. Its energy is conserved within the closed system.

What are time crystals used for?

Currently, time crystals aren’t used for anything. In the future, they may be used as a way to store stable memory in quantum computing.

What are time crystals made of?

Time crystals aren’t “made” of anything but are systems of oscillating particles resistant to entropy. These systems can be created using all sorts of matter, with recent experiments using nitrogen impurities within a diamond, and another using ytterbium ions.

What do time crystals look like?

The only time crystals that have been made are only visible at an atomic level. They appear as a system of atoms that can be seen by watching their magnetic fields.

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