
Physicists Aim to Classify All Possible Phases of Matter - jonbaer
https://www.quantamagazine.org/physicists-aim-to-classify-all-possible-phases-of-matter-20180103/
======
mathgenius
I've just finished a PhD in this area, topological quantum memories.

Totally amazed at the level of this quantamagazine article. Superb stuff. They
even manage to explain string-nets. I keep thinking that you could make an
interesting iPhone game out of this.

Actually it's nice to read a bit of a summary of the field, including the
history.

Here is another good article discussing the open problem of the existence of a
quantum memory [1]. The story goes like this: your hard-drive stores bits of
information in little magnets. That is magnetic order, which falls into the
symmetry-breaking paradigm discussed in the article. When you turn the
computer off, it remembers what's on your harddrive. Those magnets keep the
bits protected, by virtue of the "magnetic order". Now here's the question:
can we do the same thing with quantum bits? Even theoretically, is it
possible? Is there some kind of "quantum ordered system" that will protect a
qubit?

[1] [https://arxiv.org/abs/1411.6643](https://arxiv.org/abs/1411.6643)

~~~
igravious
> When you turn the computer off, it remembers what's on your harddrive.

Weird analogy. The computer doesn't remember – the individual storage units on
a hard drive don't care whether the machine around them has power or not They
are indifferent to what's going on in the system which contains them as
opposed to, say, the storage units in DRAM. Are you trying to say that at the
moment all qubits we've made behave like the storage units in DRAM? In other
words, while the system that contains them is powered on they remain in the
same state but when the power is removed they become disordered? Aren't qubits
an abstraction? I mean, qubit : bit :: qubit storage unit X : harddrive bit –
or – qubit : bit :: qubit storage unit Y : DRAM bit – see what I mean?

~~~
mathgenius
Yeah this quantum memory is a passive memory, as opposed to active error
correction, which is perhaps more akin to the DRAM side of things. The active
error correction is what google etc. are working on right now. It's not clear
if passive quantum memories will ever be built, or as i said, if they even can
be theoretically built.

~~~
igravious
Cool, that's what I was trying to find out from you. Is this [Quantum Error
Correction for Quantum
Memories]([https://arxiv.org/abs/1302.3428](https://arxiv.org/abs/1302.3428))
from 2013, rev. 2015 by Barbara M. Terhal representative of the state of the
art?

~~~
mathgenius
Yes this looks like a good reference.

------
indescions_2018
Fascinating work. Not only does it get at the very heart of connecting Nature
with Mathematics. But there are some interesting novel electronics that can
result.

A Rechargeable Spin Battery

[http://advances.sciencemag.org/content/3/4/e1602531](http://advances.sciencemag.org/content/3/4/e1602531)

More broadly is the emerging field of "Materials Informatics". Roughly ML
algorithms applied to the search of stable new materials phases. As well as
the processes required to create them.

Machine learning in materials informatics: recent applications and prospects

[https://www.nature.com/articles/s41524-017-0056-5](https://www.nature.com/articles/s41524-017-0056-5)

Quantum Espresso: an integrated suite of Open-Source computer codes for
electronic-structure calculations and materials modeling at the nanoscale

[http://www.quantum-espresso.org/](http://www.quantum-espresso.org/)

------
platz
Are there even a finite number of phases, or are they more of a continuous
distribution, because they not truly fundamental?

~~~
gus_massa
At least in almost/many/same materials the liquid and the gas phase are really
one.
[https://en.wikipedia.org/wiki/Critical_point_(thermodynamics...](https://en.wikipedia.org/wiki/Critical_point_\(thermodynamics\))

I never heard about something similar with the other phases ...

------
tritium
If I’m understanding the fundamentals of the science behind this article,
basically researchers are messing around with the state of the orbitals [0] of
the electron clouds of individual atoms and molecules in very cold condensates
that are otherwise stable, provoking interesting states that defy the usual
macroscopic interactions commonly observed in the 4 classic phases of matter?

[0]
[https://en.wikipedia.org/wiki/Atomic_orbital](https://en.wikipedia.org/wiki/Atomic_orbital)

Is that about right?

~~~
goldenkey
The discrete/continuous analog would cellular automata and PDEs respectively.

Essentially, even if interaction is taking place, the hope is that such a
regular and patterned formation could keep the qbits you care about, in
perfect shape. There may be other interacting factors that oscillate but they
are not used for storage, just for nonvolatility.

------
danharaj
Betcha the theory turns out to be intractable because it'll be possible to
encode the behaviors of algorithms into the properties of such ordered matter.

~~~
contravariant
Since cellular automatons are kind of Turing complete there does seem to be a
chance that could happen.

------
k_sze
Just me or the first sentence of the article can’t be parsed?

~~~
grzm
This one?

> _" In the last three decades, condensed matter physicists have discovered a
> wonderland of exotic new phases of matter: emergent, collective states of
> interacting particles that are nothing like the solids, liquids and gases of
> common experience."_

Stripped of most everything, the sentence reduces to _" Physicists have
discovered a wonderland"_.

I'm almost wishing I could embed a graphic. It's been a while since I've
diagrammed the grammar of a sentence. I wonder if students are still being
taught how to do that. As an exercise, more for myself than what I actually
think you need, I'll just do the rest:

\- What kind of physicists? Condensed matter physicists.

\- When have the physicists discovered this wonderland? In the last three
decades.

\- A wonderland of what? Of exotic new phases of matter.

\- What are these new phases like? They're emergent, collective states of
interacting particles that are nothing like the solids, liquids and gases of
common experience.

I hope that was the sentence you were referring to :)

~~~
k_sze
Oh. Physicists in the area of condensed matter. Got it.

I would have written “condensed-matter” with a hyphen to make it more obvious
that it’s being used as an adjective.

~~~
jeffwass
Condensed matter physics is a long-standing branch of physics study, similar
to high energy physics and astrophysics.

The physics dept of any university should have a condensed matter subgroup,
both theory and experimental.

(FYI - I did my PhD in experimental condensed matter physics).

[https://en.m.wikipedia.org/wiki/Condensed_matter_physics](https://en.m.wikipedia.org/wiki/Condensed_matter_physics)

