12 ms·

Feeling resigned to just not understanding this one as a lay person. Oh well, hope it leads to more cool things!

by ttpphd 4y ago

im3w1l 4y ago
It's wrong to say that a quasi-crystal is crystal from a higher dimension. You apparently get a quasi-crystal if you project a higher dimensional crystal, which I guess is neat. But really they are just trying to hype up their own results.
jerf 4y ago
"Feeling resigned to just not understanding this one as a lay person." The biggest and most important step is to make sure you drop any mysticism about what a "dimension" is. It's just a necessary component of identifying the location of something in some way. More than three "dimensions" is not just common but super common, to the point of mundanity. The location and orientation of a rigid object, a completely boring quantity, is six dimensional: three for space, three for the rotation. Add velocity in and it becomes 12 dimensional; the six previous and three each now for linear and rotational velocity. To understand "dimensions" you must purge ALL science fiction understanding and understand them not as exotic, but painfully mundane and boring. (They may measure something interesting, but that "interestingness" should be accounted to the thing being measured, not the "dimension". "Dimensions" are as boring as "inches" or "gallons".) Next up, there is a very easy metaphor for us in the computing realm for the latest in QM and especially materials science. In our world, there is a certain way in which a "virtual machine" and a "machine" are hard to tell apart. A lot of things in the latest QM and materials science is building little virtual things that combine the existing simple QM primitives to build new systems. The simplest example of this sort of thing is a "hole". Holes do not "exist". They are where an electron is missing. But you can treat them as a virtual thing, and it can be difficult to tell whether or not that virtual thing is "real" or not, because it acts exactly like the "virtual" thing would if it were "real". In this case, this system may mathematically behave like there is a second time dimension, and that's interesting, but it "just" "simulating" it. It creates a larger system out of smaller parts that happens to match that behavior, but it doesn't mean there's "really" a second time dimension. The weird and whacky things you hear coming out of QM and materials science are composite things being assembled out of normal mundane components in ways that allow them to "simulate" being some other interesting system, except when you're "simulating" at this low, basic level it essentially is just the thing being "simulated". But there's not necessarily anything new going on; it's still electrons and protons and neutrons and such, just arranged in interesting ways, just as, in the end, Quake or Tetris is "just" an interesting arrangement of NAND gates. There's no upper limit to how "interestingly" things can be arranged, but there's less "new" than meets the eye. Unfortunately, trying to understand this through science articles, which are still as addicted as ever to "woo woo" with the word dimensions and leaning in to the weirdness of QM and basically deliberately trying to instill mysticism at the incorrect level of the problem. (Personally, I still feel a lot of wonder about the world and enjoy learning more... but woo woo about what a "dimension" is is not the place for that.)
- philipswood 4y ago
  Yeah, extra spatial dimensions might be common as grass in visualisations, but extra TIME dimensions... those are pretty unusual.
- deanCommie 4y ago
  This may be the most eye-opening and clarifying thing I've read about this domain in literally years. Thank you. The connection back to the complexity chasm that exists between NAND gates and Quake is also fantastic because as a "traditional" software engineer, it makes perfect sense. It's also good remembering that most of the "academic science" that underlies computers was established almost 100 years ago. But it took this long for us to get GTA Online. Whatever advances arrive from these developments in Quantum computing may not see practical groundbreaking applications until we're all very old and decrepit. It's still incredible to hear about. The fact that our modern "wireless" world exists on fundamentally the same physical primitives as a radio wave pulsing morse code bouncing it off the ionosphere 100 years ago is mindboggling.
- phkahler 4y ago
  They could have just said "aperiodic laser pulses" are used. No need to introduce fantastical sounding terminology about multiple time dimensions, which seems to have been done quite deliberately.
- lucasgw 4y ago
  This is a really wonderful explanation that removes the woo from QM. As a non-scientist, I've spent a lot of time reading about QM and trying to understand stuff, and eventually get lost in hand-waviness about dimensions and vague references to Schrodinger and his boxes of semi-cats. Thanks!!
kmeisthax 4y ago
Ok, so let's cut through the woo: A crystal is a repeating pattern of elements in space. For example, a diamond is carbon atoms - the same thing in ordinary coal - arranged in a particular shape of grid. You can have patterns that are made in time rather than space, such as by hitting a drum with a stick in time with music. Of course, this isn't really very crystal-like, because the drum doesn't try to resist you hitting it off-time. However, there are certain atomic-scale materials that do resist your horrible off-beat drumming, and you "hit" them with a laser rather than a drumstick. These systems are time crystals[0]. You can also have crystal patterns that don't repeat, which are called quasicrystals. For every quasicrystal, there's a higher-dimension crystal that it is a shadow of. You could imagine, say, a 3D grid or lattice that you can shine a light through onto a piece of paper to get an irregular 2D pattern, which would be your quasicrystal. The two structures are related to one another, but that doesn't necessarily mean that the flatlanders living in it have proof of the existence of a third dimension. The new development is time quasicrystals: i.e. a drum that you can bang with some non-repeating pattern and it will also keep in time with the pattern even if you are off. The stuff about "acting like it has two time dimensions" is more woo; there is a 2D time relation to the 1D time quasicrystal, but there is no actual 2D time shenanigans going on. The non-repeating pattern apparently also makes the time crystal better at "keeping time" which may help build more stable qubits for quantum computers. [0] Note that you can't have spacetime crystals in the same material. You can either have atoms that link to one another with chemical bonds to form a pattern, or atoms that trade their bonds in rhythmic patterns, but not both.
- function_seven 4y ago
  > You could imagine, say, a 3D grid or lattice that you can shine a light through onto a piece of paper to get an irregular 2D pattern, which would be your quasicrystal. This is where I lose it. I actually can't imagine such a thing. Every regular 3D crystal I imagine has a repeating pattern in its shadow. For every ray of light passing through one part of the 3D lattice, I can locate parallel rays that produce the same result in other parts of the lattice. What am I missing here? Just not imagining the right lattice types? Or are we assuming a point-source of light so that no 2 rays are parallel?
xkcd-sucks 4y ago
If you look at the graphic at the top of the article (Penrose tiling) you'll notice there are a bunch of points that are centers of rotational symmetry (you can rotate it 2pi/N and get the same thing) and lines of reflection symmetry (you can mirror it over that line and get the same thing) but there is no translational symmetry (you can't slide it over in any direction and overlap with the original), this is a "quasicrystal" (in 2d) Compare to e.g. a grid of squares that has reflection and rotation symmetry but also has translational symmetry, this is a true "crystal" (in 2d) This article is treating a train of laser pulses as a "1d crystal" and if long/short pulses resemble a Fibonacci sequence treating it as a "1d quasicrystal". This seems to be noteworthy in that using such a structured pulse train provides some improvements in quantum computing when it's used to read / write (i.e. shine on) information (i.e. electron configuration) from atoms / small molecules (i.e. qubits) Edit: And the "2 time dimensions" thing is basically that a N-d "quasicrystal" is usually a pretty close approximation of an [N+M]-d "true crystal" projected down into N dimensions so the considering the higher dimension structure might make things easier by getting rid of transcendental numbers etc.
deleted 4y ago
[deleted]

Feeling resigned to just not understanding this one as a lay person. Oh well, hope it leads to more cool things!

by ttpphd 4y ago

Feeling resigned to just not understanding this one as a lay person. Oh well, hope it leads to more cool things!

It's wrong to say that a quasi-crystal is crystal from a higher dimension. You apparently get a quasi-crystal if you project a higher dimensional crystal, which I guess is neat. But really they are just trying to hype up their own results.

jerf 4y ago

"Feeling resigned to just not understanding this one as a lay person." The biggest and most important step is to make sure you drop any mysticism about what a "dimension" is. It's just a necessary component of identifying the location of something in some way. More than three "dimensions" is not just common but super common, to the point of mundanity. The location and orientation of a rigid object, a completely boring quantity, is six dimensional: three for space, three for the rotation. Add velocity in and it becomes 12 dimensional; the six previous and three each now for linear and rotational velocity. To understand "dimensions" you must purge ALL science fiction understanding and understand them not as exotic, but painfully mundane and boring. (They may measure something interesting, but that "interestingness" should be accounted to the thing being measured, not the "dimension". "Dimensions" are as boring as "inches" or "gallons".) Next up, there is a very easy metaphor for us in the computing realm for the latest in QM and especially materials science. In our world, there is a certain way in which a "virtual machine" and a "machine" are hard to tell apart. A lot of things in the latest QM and materials science is building little virtual things that combine the existing simple QM primitives to build new systems. The simplest example of this sort of thing is a "hole". Holes do not "exist". They are where an electron is missing. But you can treat them as a virtual thing, and it can be difficult to tell whether or not that virtual thing is "real" or not, because it acts exactly like the "virtual" thing would if it were "real". In this case, this system may mathematically behave like there is a second time dimension, and that's interesting, but it "just" "simulating" it. It creates a larger system out of smaller parts that happens to match that behavior, but it doesn't mean there's "really" a second time dimension. The weird and whacky things you hear coming out of QM and materials science are composite things being assembled out of normal mundane components in ways that allow them to "simulate" being some other interesting system, except when you're "simulating" at this low, basic level it essentially is just the thing being "simulated". But there's not necessarily anything new going on; it's still electrons and protons and neutrons and such, just arranged in interesting ways, just as, in the end, Quake or Tetris is "just" an interesting arrangement of NAND gates. There's no upper limit to how "interestingly" things can be arranged, but there's less "new" than meets the eye. Unfortunately, trying to understand this through science articles, which are still as addicted as ever to "woo woo" with the word dimensions and leaning in to the weirdness of QM and basically deliberately trying to instill mysticism at the incorrect level of the problem. (Personally, I still feel a lot of wonder about the world and enjoy learning more... but woo woo about what a "dimension" is is not the place for that.)

philipswood 4y ago
Yeah, extra spatial dimensions might be common as grass in visualisations, but extra TIME dimensions... those are pretty unusual.
deanCommie 4y ago
This may be the most eye-opening and clarifying thing I've read about this domain in literally years. Thank you. The connection back to the complexity chasm that exists between NAND gates and Quake is also fantastic because as a "traditional" software engineer, it makes perfect sense. It's also good remembering that most of the "academic science" that underlies computers was established almost 100 years ago. But it took this long for us to get GTA Online. Whatever advances arrive from these developments in Quantum computing may not see practical groundbreaking applications until we're all very old and decrepit. It's still incredible to hear about. The fact that our modern "wireless" world exists on fundamentally the same physical primitives as a radio wave pulsing morse code bouncing it off the ionosphere 100 years ago is mindboggling.
phkahler 4y ago
They could have just said "aperiodic laser pulses" are used. No need to introduce fantastical sounding terminology about multiple time dimensions, which seems to have been done quite deliberately.
lucasgw 4y ago
This is a really wonderful explanation that removes the woo from QM. As a non-scientist, I've spent a lot of time reading about QM and trying to understand stuff, and eventually get lost in hand-waviness about dimensions and vague references to Schrodinger and his boxes of semi-cats. Thanks!!

kmeisthax 4y ago

Ok, so let's cut through the woo: A crystal is a repeating pattern of elements in space. For example, a diamond is carbon atoms - the same thing in ordinary coal - arranged in a particular shape of grid. You can have patterns that are made in time rather than space, such as by hitting a drum with a stick in time with music. Of course, this isn't really very crystal-like, because the drum doesn't try to resist you hitting it off-time. However, there are certain atomic-scale materials that do resist your horrible off-beat drumming, and you "hit" them with a laser rather than a drumstick. These systems are time crystals[0]. You can also have crystal patterns that don't repeat, which are called quasicrystals. For every quasicrystal, there's a higher-dimension crystal that it is a shadow of. You could imagine, say, a 3D grid or lattice that you can shine a light through onto a piece of paper to get an irregular 2D pattern, which would be your quasicrystal. The two structures are related to one another, but that doesn't necessarily mean that the flatlanders living in it have proof of the existence of a third dimension. The new development is time quasicrystals: i.e. a drum that you can bang with some non-repeating pattern and it will also keep in time with the pattern even if you are off. The stuff about "acting like it has two time dimensions" is more woo; there is a 2D time relation to the 1D time quasicrystal, but there is no actual 2D time shenanigans going on. The non-repeating pattern apparently also makes the time crystal better at "keeping time" which may help build more stable qubits for quantum computers. [0] Note that you can't have spacetime crystals in the same material. You can either have atoms that link to one another with chemical bonds to form a pattern, or atoms that trade their bonds in rhythmic patterns, but not both.

function_seven 4y ago
> You could imagine, say, a 3D grid or lattice that you can shine a light through onto a piece of paper to get an irregular 2D pattern, which would be your quasicrystal. This is where I lose it. I actually can't imagine such a thing. Every regular 3D crystal I imagine has a repeating pattern in its shadow. For every ray of light passing through one part of the 3D lattice, I can locate parallel rays that produce the same result in other parts of the lattice. What am I missing here? Just not imagining the right lattice types? Or are we assuming a point-source of light so that no 2 rays are parallel?

xkcd-sucks 4y ago

If you look at the graphic at the top of the article (Penrose tiling) you'll notice there are a bunch of points that are centers of rotational symmetry (you can rotate it 2pi/N and get the same thing) and lines of reflection symmetry (you can mirror it over that line and get the same thing) but there is no translational symmetry (you can't slide it over in any direction and overlap with the original), this is a "quasicrystal" (in 2d) Compare to e.g. a grid of squares that has reflection and rotation symmetry but also has translational symmetry, this is a true "crystal" (in 2d) This article is treating a train of laser pulses as a "1d crystal" and if long/short pulses resemble a Fibonacci sequence treating it as a "1d quasicrystal". This seems to be noteworthy in that using such a structured pulse train provides some improvements in quantum computing when it's used to read / write (i.e. shine on) information (i.e. electron configuration) from atoms / small molecules (i.e. qubits) Edit: And the "2 time dimensions" thing is basically that a N-d "quasicrystal" is usually a pretty close approximation of an [N+M]-d "true crystal" projected down into N dimensions so the considering the higher dimension structure might make things easier by getting rid of transcendental numbers etc.

deleted 4y ago

[deleted]