New state of matter - topological states & topocunductors

[Ender]

Microsoft says they discovered a new state of matter & submitted a research paper to nature.

Can anyone help me understand what they mean by a topological state of matter?

Meanwhile, Nature publishes this: Microsoft claims quantum-computing breakthrough — but some physicists are sceptical

 

[Cmaier]

It’s all a bit misleading.

Traditional states of matter (gas, solid, liquid, plasma) are defined by the organization and arrangement of the atoms that make up the matter. In other words, by the way the atoms are arranged in space.

But you can have matter that’s in one of those states (say, solid) that also has a “topological” state. Topological states are not determined by the spatial arrangement of the atoms, but are instead determined by the quantum relationship between the particles in the matter.

The topological states is determined by the pattern of the quantum entanglement between the particles. There are multiple possible topological states, all of which require extreme cold - near absolute zero - to be possible.

As for quantum entanglement, that refers to the spooky fact that for certain tiny particles, a property of one particle is tied to a property of another particle. If one particle spins one way, the other has to spin the other. (It gets spookier because you can do experiments that prove that neither particle’s spin is actually determined until you measure it, and once you measure one, the other suddenly has the opposite spin, even thought the two particles are not near each other and cannot have communicated with each other).

 

[Ender]

hmm so rather than the arrangement of atoms in what we traditionally call physical space, it’s about the arrangement of the particle wave’s (that make up the atoms) entanglement with each other?

 

[Cmaier]

hmm so rather than the arrangement of atoms in what we traditionally call physical space, it’s about the arrangement of the particle wave’s (that make up the atoms) entanglement with each other?

Essentially, yes.

 

[cbum]

I've never been able to wrap my head around that spooky action at a distance - in fact, every time I get entangled with the idea, my brain collapses...

It would seem to me that we are missing something in that story, like a separate factor, orthogonal to the spin, that is linked to the spin direction and is created/determined at the time of entanglement (freezing), as (unobserved) part of the particle, ensuring that at the time of collapse/measurment, the two particles end up with opposite spin...???

 

[casperes1996]

As for quantum entanglement, that refers to the spooky fact that for certain tiny particles, a property of one particle is tied to a property of another particle. If one particle spins one way, the other has to spin the other. (It gets spookier because you can do experiments that prove that neither particle’s spin is actually determined until you measure it, and once you measure one, the other suddenly has the opposite spin, even thought the two particles are not near each other and cannot have communicated with each other).

This is just the developers of the simulation who implemented an optimisation they didn't expect to matter for the effects or for us to figure out. "Just render the accurate spin whenever anyone looks at it, until then it doesn't matter". Like LODs

 

[Cmaier]

I've never been able to wrap my head around that spooky action at a distance - in fact, every time I get entangled with the idea, my brain collapses...

It would seem to me that we are missing something in that story, like a separate factor, orthogonal to the spin, that is linked to the spin direction and is created/determined at the time of entanglement (freezing), as (unobserved) part of the particle, ensuring that at the time of collapse/measurment, the two particles end up with opposite spin...???

having taken classes in post-graduate-level quantum mechanics, the trick to wrapping your head around it is to just accept it and not try to analogize it to anything you are physically used to. Once I decided that the concept of physical space is just an illusion that quantum particles aren’t subject to, my grades improved. (Same applies to the concept of time, though the experiment where measuring one particle at time X causes the probability wave to collapse for another particle at time X-1 didn’t happen yet by the time I took quantum).

 

[throAU]

having taken classes in post-graduate-level quantum mechanics, the trick to wrapping your head around it is to just accept it and not try to analogize it to anything you are physically used to. Once I decided that the concept of physical space is just an illusion that quantum particles aren’t subject to, my grades improved. (Same applies to the concept of time, though the experiment where measuring one particle at time X causes the probability wave to collapse for another particle at time X-1 didn’t happen yet by the time I took quantum).

For weird abstract thinking like this I strongly recommend listening to/reading some material by Donald Hoffman.

Donald D. Hoffman - Wikipedia

en.wikipedia.org

Specifiically his "MUI theory".

Not specifically quantum physics related but a mind bending theory on how our senses evolved and how they have absolutely no bearing on physical reality, just what our bodies have determined to be the minimum of useful information to survive. Because things that aren't useful for our brain to perceive and process are just burned energy (and thus, more expense in terms of energy requirements, etc.) for nothing useful. e.g., we can't see in ultraviolet or infrared (like some animals) because for us it is evolutionarily irrelevant to our needs.

With that out of the way, as above - quantum physics is something our brains can't really comprehend (probably because we've never evolved to deal with it), but experimental evidence suggests is legitimate. Just accept the weirdness

I'm not a physicist but I suspect the "spooky action at a distance" is essentially because the entangled particles are still "connected" together via a dimension other than time or space(?). i.e., you can move them as far as you like in the 3d space, but without relocating them in some other dimension we can not perceive, they're still "connected".

 

[ArgoDuck]

^ … there is a division of thought among physicists, with most accepting ‘this is just how reality is, and the best description we are able to develop’. Others, including the formidable mathematician and cosmologist Roger Penrose, do think there is hidden order. Yet for all his formidable skills and imagination, he hasn’t provided an alternative (to be fair, his tastes lie more in cosmology and pure mathematics).

There have been a number of interesting papers in recent years nibbling away at quantum mechanics and showing - for example - that at least parts of it can be derived from first principles. (I don’t pretend to understand these papers - even though i still read them from time to time! My math/physics BSc dates back to the 1970s!).

I agree…we’re (most of us anyway) simply not built to understand this stuff. It lies too far outside our everyday experience.

 

[Nycturne]

There have been a number of interesting papers in recent years nibbling away at quantum mechanics and showing - for example - that at least parts of it can be derived from first principles. (I don’t pretend to understand these papers - even though i still read them from time to time! My math/physics BSc dates back to the 1970s!).

Yeah, QM is basically this whole mass of stuff we are chipping away at trying to get an insight here or there to help understand it better.

And things like "how does entanglement actually work" gets to pretty foundational concepts of "what is spacetime anyways?" which we really don't know as much about as we thought. As you point out, what we're learning about the universe is way outside our day to day experience, but since our experience includes things such as "space" and "time", it gets rough thinking that those things might even simply be emergent behaviors of some underlying system that we can only probe like one would try to determine how a black box works.

Holographic principle is another one of these things that shows up in the math when looking at the boundaries of entropy (black holes), but we just have no idea wether or not its also applicable to the universe. Maybe, maybe not.

But you can have matter that’s in one of those states (say, solid) that also has a “topological” state. Topological states are not determined by the spatial arrangement of the atoms, but are instead determined by the quantum relationship between the particles in the matter.

The topological states is determined by the pattern of the quantum entanglement between the particles. There are multiple possible topological states, all of which require extreme cold - near absolute zero - to be possible.

I don't think it helps that the Microsoft article in particular is very vague on the topological state they claim to have discovered, just that they are using a topological state for stability of the qubits. Which, apparently superconducting qubits (where superconductivity is a topological state I believe?) are something multiple companies have been working on, so it would help if Microsoft clarified their claims a bit in some way here.

 

[Yoused]

One of the key principles to QC is "tunneling". A particle is in a given state, and for it to change state, it has to overcome an energy barrier (energy has to be added to it for its state to change). But, sometimes a particle can change state without the applied energy: it "tunnels" through the energy barrier instead of surmounting it. The states of the qubits may change in distinct ways because some of their particles have tunneled through. The qubit is designed to allow tunneling (which relies largely on the low temperatures) in somewhat predictable ways, which, I think, is where the "topology" part comes in.

Once I decided that the concept of physical space is just an illusion that quantum particles aren’t subject to, my grades improved. (Same applies to the concept of time, though the experiment where measuring one particle at time X causes the probability wave to collapse for another particle at time X-1 didn’t happen yet by the time I took quantum).

Mechanists want to see time in geometric terms, but those are not really applicable. We think of "the present" as a sort of wall between the past and the future, but it is not at all like that. GR and SR tell us that any given location experiences a present that is different from any other location. "Right now" on Mars simply cannot be correlated to right now on Earth. In fact, it has even been possible to measure the GR-effective difference between San Jose and Denver. Your "this very moment" will ultimately not correspond to mine in a meaningful way.

The present moment is not a flat surface, the way it is conveniently depicted in the math, but a blurry diffusion of "about now", which is one reason QM has difficulty with exact measurements (not the only reason).

Add to that the fact that the past is not a physical thing but effectively just information about how we got here. And the one thing we know about information is that it is flexible. The past literally changes as we acquire information pertaining to what happened. It is all Rashomon, all the time. The future is what will probably happened, based on what we thing happened in the past (i.e., "determinism" is nonsense).