http://www.sciencealert.com/scientists-have-just-announced-a-brand-new-form-of-matter-time-crystals
Still trying to get my head around it, but it looks intriguing.
Quote from: Gloucester on February 16, 2017, 09:25:49 PM
http://www.sciencealert.com/scientists-have-just-announced-a-brand-new-form-of-matter-time-crystals
Still trying to get my head around it, but it looks intriguing.
You and me both! I've spent some time trying to learn what a time crystal actually is, and the most non-physicist-friendly explanation I've found so far is from MIT Technology Review (https://www.technologyreview.com/s/602541/physicists-create-worlds-first-time-crystal/).
I don't understand....If it repeats in time, what makes that different from a regular crystal?
Ok, I read these 2 articles and tried really super hard to get a little grasp on the concept at least, but it's mostly beyond my understanding....
So I'm curious, what would we do with these time crystals, if we could harness them? What applications might they have? Because I don't understand what "quantum memory" means. :o
Quote from: Dragonia on February 18, 2017, 12:33:44 AM
Ok, I read these 2 articles and tried really super hard to get a little grasp on the concept at least, but it's mostly beyond my understanding....
So I'm curious, what would we do with these time crystals, if we could harness them? What applications might they have? Because I don't understand what "quantum memory" means. :o
Good question. :thinking:
...
Very good question. :teadrink:
Quote from: Dragonia on February 18, 2017, 12:33:44 AM
Ok, I read these 2 articles and tried really super hard to get a little grasp on the concept at least, but it's mostly beyond my understanding....
So I'm curious, what would we do with these time crystals, if we could harness them? What applications might they have? Because I don't understand what "quantum memory" means. :o
In one of the articles I read they mentioned the possible use of time crystals in developing a quantum computer. Quantum computers are mostly theoretical right now, though people are working on trying to create them. What follows is a rough description, but it might help give a glimpse into the ideas here.
A quantum computer uses quantum superposition (oversimplified: the ability of particles to be in multiple states), to store and manipulate information. Instead of bits being binary (either 1 or 0) as in the computers we use right now, in a quantum computer there would be more than just those two states. I don't know what the physicists who work on this concept call the non-binary states, but I'll just use fractions. So a bit in a quantum computer might be say 0 or 1/4 or 1/2 or 3/4 or 1.
However, quantum decoherence is a problem. This is the tendency of a quantum system to "forget" the state it's in as it interacts with the world. In our computers, once the bit is set to 1 or 0, it stays that way until changed, but a bit in state "3/4" in a quantum computer will sooner or later change to a different state just because the computer is being used. That's no good.
Time crystals, according to the Wikipedia article (https://en.wikipedia.org/wiki/Space-time_crystal) I read, resist this quantum decoherence. If they could be used in quantum computers that would help solve the problem I described.
I'm pretty sure the above isn't precisely accurate, as I said, and I would welcome any corrections, but it's what I've understood from the articles I've read, and from previous reading about quantum mechanics.
Quote from: Dragonia on February 18, 2017, 12:33:44 AM
Ok, I read these 2 articles and tried really super hard to get a little grasp on the concept at least, but it's mostly beyond my understanding....
So I'm curious, what would we do with these time crystals, if we could harness them? What applications might they have? Because I don't understand what "quantum memory" means. :o
Somebody once asked what use the laser was.
And what use the telephone? There were enough telegraph boys for those important enough to need to send urgent messages.
Etc.
You never know 'till you know.
Ok... so I also found this article:
https://physics.aps.org/articles/v5/116 (https://physics.aps.org/articles/v5/116)
with this picture:
(https://physics.aps.org/assets/4f49767f-2335-4bac-aaae-cb30cee4cdaa/e116_1.png)
I get quantum computing (mostly), but still haven't got a clue on Time Crystals.
Quote from: joeactor on February 18, 2017, 04:04:00 PM
I get quantum computing (mostly), but still haven't got a clue on Time Crystals.
Don't they power the TARDIS :)?
So would a time crystal still have motion at zero Kelvin?
Quote from: Tom62 on February 18, 2017, 05:05:04 PM
Quote from: joeactor on February 18, 2017, 04:04:00 PM
I get quantum computing (mostly), but still haven't got a clue on Time Crystals.
Don't they power the TARDIS :)?
:puppysnicker:
I guess if it repeats in time then it can (seemingly) be in 2 places at once. Or is that a worm hole? Idk.
Quote from: Arturo on February 19, 2017, 01:54:46 AMI guess if it repeats in time then it can (seemingly) be in 2 places at once. Or is that a worm hole? Idk.
The idea is that elements of a time crystal (ytterbium atoms in one of the experiments) move in a repeating pattern even when there is no energy being imparted to the system (the "ground state"). Normal matter in its ground state is in equilibrium; basically motionless. The matter in a time crystal theoretically never reaches equilibrium. Elements of a time crystal are not in two places at the same time, but periodically they return to the same place.
I looked on YouTube for videos that explain what the scientists say is going on, and found several--all of them rather annoying, in various different ways. What is it with the roboticised voices? Three of the videos I found used this ridiculous gimmick. The one below has an OK explanation--the voice is roboticised, but not quite as thoroughly as the other two. ::)
Oh ok. I understood the part where it seems to jiggle but has no energy. But maybe that's just me because my brain likes things that contradict.
New development--as I understand it they've made a digital model of a time crystal. I don't know that anything in the article or the paper makes the concept clearer though. :-\
"'An ever-ticking clock': we made a 'time crystal' inside a quantum computer" |
The Conversation (https://theconversation.com/an-ever-ticking-clock-we-made-a-time-crystal-inside-a-quantum-computer-178164)
QuoteComputers are all around us. Some are compact, portable and primarily used to stream Netflix, while others fill entire rooms and simulate complex phenomena like the weather or the evolution of our Universe.
Regardless of the details, on a fundamental level computers all have the same purpose: processing information. The information is stored and processed in "bits".
Any physical system with two identifiably distinct states (call them "0" and "1") can serve as a bit. Connect lots of bits together in the right way and you can do arithmetic, logic, or what we generally call "computation".
(https://i.imgur.com/lJRuibR.png)
Now, it turns out that the physical world on a very fundamental level is governed by the strange rules of quantum physics. You can also make a quantum version of a bit, called a quantum bit or "qubit".
Qubits can also be described in terms of two states, "0" and "1", except they can be both "0" and "1" at the same time. This allows for a much richer form of information processing, and hence more powerful computers.
Much of the current research in this area is focused either on building a working quantum computer – a challenging engineering task indeed – or on designing algorithms to do things we can't manage with our current, classical computers.
Our research, however, is focused on an application first envisioned by the famous US physicist Richard Feynman more than 30 years ago: to use quantum computers to conduct research in fundamental physics.
[Continues . . . (https://theconversation.com/an-ever-ticking-clock-we-made-a-time-crystal-inside-a-quantum-computer-178164)]
The paper is open access:
"Realization of a discrete time crystal on 57 qubits of a quantum computer" |
Science Advances (https://www.science.org/doi/10.1126/sciadv.abm7652)
QuoteAbstract:
Unconventional dynamical phases that violate ergodicity (https://en.wikipedia.org/wiki/Ergodicity) have been a subject of extensive research in recent years. A periodically driven system is naively expected to lose all memory of its initial state due to thermalization, yet this can be avoided in the presence of many-body localization. A discrete time crystal represents a driven system whose local observables spontaneously break time translation symmetry and retain memory of the initial state indefinitely.
Here, we report the observation of a discrete time crystal on a chain consisting of 57 superconducting qubits on a state-of-the-art quantum computer. We probe random initial states and compare the cases of vanishing and finite disorder to distinguish many-body localization from prethermal dynamics. We further report results on the dynamical phase transition between the discrete time crystal and a thermal regime, which is observed via critical fluctuations in the system's subharmonic frequency response and a substantial speedup of spin depolarization.
Sticking with this topic, despite not really having a grasp of the concept that I find satisfying. This development doesn't do anything to improve the situation. :-\
"A New Kind of Time Crystal Has Been Created That Does Interesting Things to Light" |
Science Alert (https://www.sciencealert.com/a-new-kind-of-time-crystal-has-been-created-that-does-interesting-things-to-light)
QuoteScientists are still getting to grips with the ins and outs of strange materials known as time crystals; structures that buzz with movement for eternity. Now a new variety might help deepen our understanding of the perplexing state of matter.
Just as regular crystals are atoms and molecules that repeat over a volume of space, time crystals are collections of particles that tick-tock in patterns over a duration of time in ways that initially seem to defy science.
Theorized in 2012 before being observed in the lab for the first time just four years later, researchers have been busy tinkering with the structures to probe deeper foundations of particle physics and uncover potential applications.
In this latest study, a new kind if 'photonic' time crystal has been created. Operating at microwave frequencies, it is able to neaten and amplify electromagnetic waves, promising future applications in wireless communication systems, laser development, and electronic circuits.
"In a photonic time crystal, the photons are arranged in a pattern that repeats over time," says (https://www.aalto.fi/en/news/a-new-type-of-photonic-time-crystal-gives-light-a-boost) lead author Xuchen Wang, a nano engineer from the Karlsruhe Institute of Technology in Germany.
"This means that the photons in the crystal are synchronized and coherent, which can lead to constructive interference and amplification of the light."
In addition, the research team found electromagnetic waves traveling along surfaces could be amplified as well as waves from the surrounding environment.
At the center of the research is a 2D approach based on ultra-thin sheets of artificial materials known as metasurfaces (https://en.wikipedia.org/wiki/Electromagnetic_metasurface). Previously, research into photonic time crystals has been through bulk 3D materials: making and studying these materials is hugely difficult for scientists, but the switch to 2D means a faster and easier route to experimentation – and to finding out how these crystals might be applied in real world settings.
[Continues . . . (https://www.sciencealert.com/a-new-kind-of-time-crystal-has-been-created-that-does-interesting-things-to-light)]
The paper is open access. ;)
"Metasurface-based realization of photonic time crystals" |
Science Advances (https://www.science.org/doi/10.1126/sciadv.adg7541)
QuoteAbstract:
Photonic time crystals are artificial materials whose electromagnetic properties are uniform in space but periodically vary in time. The synthesis of these materials and experimental observation of their physics remain very challenging because of the stringent requirement for uniform modulation of material properties in volumetric samples.
In this work, we extend the concept of photonic time crystals to two-dimensional artificial structures—metasurfaces. We demonstrate that time-varying metasurfaces not only preserve key physical properties of volumetric photonic time crystals despite their simpler topology but also host common momentum bandgaps shared by both surface and free-space electromagnetic waves.
On the basis of a microwave metasurface design, we experimentally confirmed the exponential wave amplification inside a momentum bandgap and the possibility to probe bandgap physics by external (free-space) excitations. The proposed metasurface serves as a straightforward material platform for realizing emerging photonic space-time crystals and as a realistic system for the amplification of surface-wave signals in future wireless communications.
I'm with you. They sound fun but I haven't got a clue what they are.
If you are willing to be satisfied with somewhat of an oversimplification (and rather silly amateur dramatic performances in the intro) the video below from a scientist at Fermilab may be just the ticket. ;)
I've not seen any of the three movies mentioned, nor watched Dr Who. As for the crystals, my "learning" about qm is 40 years out of date. We didn't discuss them back then, there wasn't time.
:this: :rimshot:
"Radical New Time Crystal Revealed That Lasts Millions of Times Longer" |
Science Alerts (https://www.sciencealert.com/radical-new-time-crystal-revealed-that-lasts-millions-of-times-longer)
QuoteA semiconductor made from indium gallium arsenide has just set a duration record for a seemingly impossible material that repeats itself through time.
Lasting at least 40 minutes, the period of oscillations sustained by an experiment led by researchers from TU Dortmund University in Germany blew everything else in its class out of the water, setting a new benchmark in a field where researchers have struggled to push the phenomenon past a handful of milliseconds.
The 'tick-tock' of this itty-bitty clock took the form of interactions between orbiting electrons of a particular spin and the state of their atomic nuclei. In a game of pass-the-polarizing-parcel, the oscillations in states repeat in a way that matches the criteria for what's known as a continuous time crystal.
Hypothesized more than a decade ago by renowned physicist Frank Wilczek as a theoretically possible quirk of nature, the time crystal is to time what diamonds, sapphires, and quartzes are to space – repetitive units of matter.
Where a diamond is a pattern of carbon atoms in three spatial dimensions, a time crystal is some kind of change in structure repeating through time.
At first glance, oscillations of matter trapped in some kind of eternal Groundhog Day sound a little fishy. Anybody can make a child zip back and forth on a swing with a steady series of pushes, but eventually even the most desperate parent will wheeze to a halt.
Undeterred, physicists have searched for signs of wiggles and wobbles in materials that can't be explained by conventional physics, and have since come across multiple examples of time-crystal-eque activity in a variety of contexts. These typically take the form of some kind of extraneous beat in an otherwise linear rhythm, one that is provided by the system rather than a directed push from outside.
Yet these so-called discrete time crystals still require some kind of external tempo to set a background rhythm. Stop the music and the crystal's toe-tapping fun comes to a halt with it.
A continuous time crystal resembles Wilczek's vision a little more closely. While energy is still required to top up that which is lost from the system, its source isn't bound to any rules of time itself, acting like a breeze driving a wind chime into swinging with a few unexpected tinkles.
[Continues . . . (https://www.sciencealert.com/radical-new-time-crystal-revealed-that-lasts-millions-of-times-longer)]
The paper (https://www.nature.com/articles/s41567-023-02351-6) is behind a paywall.
QuoteAbstract:
Crystals spontaneously break the continuous translation symmetry of free space. Analogously, time crystals lift translational invariance in time.
Here we demonstrate a robust continuous time crystal in an electron–nuclear spin system of a semiconductor tailored by tuning the material composition. Continuous, time-independent external driving of the sample produces periodic auto-oscillations with a coherence time exceeding hours. Varying the experimental parameters reveals wide ranges in which the time crystal remains stable. At the edges of these ranges, we find chaotic behaviour with a lifted periodicity corresponding to the melting of the crystal.
The time crystal state enables fundamental studies of nonlinear interactions and has potential applications as a precise on-chip frequency standard.
Practical applications for time crystals... The Asmo tips Pudding's hat to science. :smilenod: