What’s the real science behind Google’s time crystal? (quantum computing)

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https://bigthink.com/hard-science/time-crystal/

EXCERPTS: Yet a recent article, touting a brand new discovery involving time crystals and Google’s quantum computer, claims to do just that: evade the second law of thermodynamics. Is that even right? [...]

[...] Although the article does a fine job of describing the experiments performed themselves, there is a howler of a statement made early on:

With the ability to forever cycle between two states without ever losing energy, time crystals dodge one of the most important laws of physics — the second law of thermodynamics, which states that the disorder, or entropy, of an isolated system must always increase. These bizarre time crystals remain stable, resisting any dissolution into randomness, despite existing in a constant state of flux.


There is no dodge; the second law of thermodynamics applies to closed systems, not open ones. The disorder of the system, if you include the microwave pulses and the external environment, does in fact go up, just as predicted.

The crystals oscillate between allowable states and return to their original ones when driven properly, just as their non-qubit analogues did years prior. In order to do this, the researchers needed to discriminate between external decoherence and internal thermalization, both of which can destroy the quantum state they are seeking to maintain, which itself is an admirable achievement.

Although it may be fun to claim, as the headline of the article did, that this is “otherworldly” and “could change physics forever,” it is more like imagining you have got a skillet with different sized and shaped mollusks in it and a chef who jiggles the pan in a way that makes the shelled creatures flip. Some will flip 180°, others 360°, others 540°, etc.

In the quantum world, some of these mollusks can take on in-between values, too. But after a certain number of jiggles, the mollusks all wind up the same way they started, regardless of what that specific initial configuration was. That is all the Google team is doing, but instead of mollusks or spinning atoms, they are using the eigenstates of a quantum computer.

Which, if we are being honest, is still a remarkable achievement! This is a new kind of time crystal, a new way of achieving it, and one with the potential to study non-equilibrium phases of matter on a quantum computer.

And although you have to pump energy into the system in pulses, the time crystal can, in fact, return to whatever specific state it began with, even with small imperfections occurring in the “flips,” without destroying, decohering, or losing the nature of the quantum state due to thermal instabilities. No laws are violated and the physics we know is not changed in any way, but this is a phenomenal achievement nonetheless.

In a mere nine years, we have gone from theorizing the existence of time crystals to creating them to observing them on a quantum processor. When a new field yields significant advances so quickly, it compels us to pay attention...
(MORE - many missing details)
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