If you had a Starbucks coffee today, you might have asked for some milk or cream.
The latter will eventually dissolve throughout the coffee, instead of sitting on the top, enabling the overall system to come to an equilibrium.
This irresistible drive towards thermal equilibrium, as described in the second law of thermodynamics, is 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.
Kind of like life. It starts out great, then it all goes to hell.
But what if something were to come along, that would turn all of that, on its head? What if the milk or cream didn’t mix. What if it just sat at the top?
If “time crystal” sounds pretty sci-fi that’s because they are.
Time crystals are no less than a new “phase of matter,” as researchers put it, which has been theorized for some years now as a new state that could potentially join the ranks of solids, liquids, gases, crystals and so on.
As you can imagine, time crystals are elusive … they are not standing on a street corner, waiting to be found.
But Google’s scientists now claim that their results establish a “scalable approach” to study time crystals on current quantum processors, ZDNet.com reported.
Understanding why time crystals are interesting requires a little bit of background in physics – particularly, knowledge of the second law of thermodynamics, which states that systems naturally tend to settle in a state known as “maximum entropy.”
Let’s go back to your coffee cup.
Time crystals, scientists say, 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.
To explain this better, ZDNet.com talked to Curt von Keyserlingk, lecturer at the school of physics and astronomy at the University of Birmingham, who did not participate in Google’s latest experiment.
It starts with a thought experiment: take a box in a closed system that is isolated from the rest of the universe, load it with a couple of dozens of coins and shake it a million times.
As the coins flip, tumble and bounce off each other, they randomly move positions and increasingly become more chaotic, says von Keyserlingk.
Upon opening the box, the expectation is that you will be faced with roughly half the coins on their heads side, and half on their tails.
It doesn’t matter if the experiment started with more coins on their tails or more coins on their heads: the system forgets what the initial configuration was, and it becomes increasingly random and chaotic as it is shaken.
Enter Google’s quantum processor, Sycamore, which is well known for its achievements and is now looking for some kind of useful application for quantum computing, ZDNet.com reported.
A quantum processor, by definition, is a perfect tool to replicate a quantum mechanical system, says von Keyserlingk.
In this scenario, Google’s team represented the coins in the box with qubits (units of quantum information) spinning upwards and downwards in a closed system; and instead of shaking the box, they applied a set of specific quantum operations that can change the state of the qubits, which they repeated many times.
This is where time crystals defy all expectations.
Looking at the system after a certain number of operations, or shakes, reveals a configuration of qubits that is not random, but instead looks rather similar to the original set up.
“The first ingredient that makes up a time crystal is that it remembers what it was doing initially. It doesn’t forget,” says von Keyserlingk. “The coins-in-a-box system forgets, but a time crystal system doesn’t.”
The weirdness doesn’t stop here.
Shake the system an even number of times, and you’ll get a similar configuration to the original one – but shake it an odd number of times, and you’ll get another set up, in which tails have been flipped to heads and vice-versa.
Scientists call this a break in the symmetry of time – which is why time crystals are called so, ZDNet.com reported.
Unlike the coins in the box, which get all muddled up and settle at roughly half heads and half tails, they buck the entropy law by getting stuck in a special, time-crystal state.
Newton’s second law of thermodynamics says that this simply can’t happen, but time crystals don’t seem to give a hoot about entropy.
Ponder that one for a moment.
Time crystals have been a topic of interest since 2012, when Nobel Prize-winning MIT professor Frank Wilczek started thinking about them; and the theory has been refuted, debated and contradicted many times.
Only last month, 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.
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 one thing is certain: time crystals won’t be sitting in our living rooms any time soon, as scientists have yet to find a definitive useful application for them.
That said, if what Google’s quantum computer accomplished can be replicated, then time crystals aren’t just real, but they might actually be put to some actual real world use.
The implications of such a technology for computer memory alone are hard to fathom, much less for computer processing itself.
The paper remains in pre-print and still requires peer review.
Sources: ZDNet.com, TechRadar.com, NewScientist, Craffic.co