February 25, 2021 • 41 mins
Daniel and Jorge break down the quantum world into tiny dots that have amazing properties.
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Speaker 1 (00:08):
Hey, Daniel, I found another physics related scam recently. Oh
did someone try to sell you quantum girl scott cookies? Again?
Girls cut cookies do seem to quantum tunnel into my
stomach pretty easily. I don't even have to eat him.
So then, what's the scam? I saw an ad for
a quantum television? Can you believe that? Nonsense? Actually? Wait,
(00:31):
what do you mean? This is the real thing? What
does the quantum TV do? Is it always fuzzy because
of the uncertainty principle? Yeah, you know, the word quantum
gets abused a lot, but this one time it's for real.
It's not a scam. No, quantum televisions are a real thing,
and they are extra crispy, just like a girl's Scout cookie.
(01:08):
I am or Hammaye, cartoonists and the creator of PhD comics. Hi,
I'm Daniel. I'm a particle of physicists, and I'm at
least made out of girls Scout cookies. Oh wow, you're
you're a big fan. It's for a good cause, you know,
that's why I eat them. It's for a good cause.
You know you can buy them and not eat them.
What that would be offensive? You have to throw them
(01:29):
in the trash, and you don't have to tell the
girls cuts they would know. But welcome to our podcast.
Daniel and Jorge Explain the Universe April, that kind of
irt radio in which we take our cookie fueled brains
and try to understand everything about the universe, not just
the tiny quantum particles and the crazy stuff happening in
the center of stars, but everything in between. We take
(01:53):
that immense mental journey all the way out into the
universe and back into the quantum particles and explain all
of it to you. Yeah, do you have a favorite
girl Scout cookies? Daniel? Oh, we're getting real here, huh.
I'm not gonna endorse one particular Girls Scott Cookies. I
gotta go. I think with the classic than mint. You know,
It's just it's so easy for them to tunnel into
your stomach. My spouse would be appalled at the mixing
(02:15):
of mint and chocolate. Do this taste like toothpaste to her? Yeah?
With chocolate. There's probably a reason there's no chocolate toothpaste flavor.
But there are a lot of interesting and amazing things
in this universe that we like to talk about in
this podcast. Things that are out there in the vast
reaches of space, and also things that are right here
(02:37):
at home, and things that are maybe at the tip
of your fingertip without even knowing. Yes, things that are
harder to understand even then, the combination of herbs and chocolate,
things that are weird, things that are quantum, things that
make no sense but are actually real. Yeah, because physics
reveals that the universe is a pretty weird place. It
(02:58):
doesn't always work the same way that we grew up
thinking that it worked. There's all kinds of strange things
going on, especially at the microscopic and at the quantum level. Yeah,
that's basically the job of physics is to figure out
how does the world actually work, Not the way we
thought it should work, or the way we might have
imagined it worked from our experience with rivers and rocks
(03:19):
and stuff, but the way fundamentally things actually happen. And
sometimes that's just for our edification, just to know how
the universe actually works. But sometimes it's actually useful and
we can use it to build cool new stuff. Wait,
what physics can be useful? Who told you that? Some
physicists your parents, some physicist After he told me some cookies.
(03:44):
Oh right, right, a limit or professional limit to being
a girl scout. You've never had a physics scott cookie?
Does it taste like particles? I hear the Higgs boson
is pretty tasty. Everything tastes like particles, man, everything particles.
Particles are also the only things doing any tasting. Yeah,
you're saying that physics can be useful. Physics can be useful. Yes.
(04:08):
In fact, you know, the Worldwide Web was invented at
a particle physics laboratory, and all sorts of things come
out of just like gaining knowledge about how the universe works, right,
And we all know how useful the Worldwide Web is.
That's right. It's contributed to a huge decrease in productivity worldwide.
It's like an anti useful particle there, depends on your
(04:29):
goals man of reducing work. But yeah, well I do
admit this useful to know physics, for sure, and sometimes
we can use that knowledge to build amazing and and
cool things that we couldn't do before. And that includes
maybe quantum mechanics, which is like the weirdest and most
awesomest thing in the universe. It is, and our understanding
(04:50):
quantum mechanics underlies most modern electronics. It's the reason that
your phone works, it's the reason your computer boots up.
It's also the reason your computer crashes. I guess no,
that's the fault of the girls got cookie crumples that
fell in my keywork. It's like a physical virus infecting
your computer. Yeah, quantum mechanics helps us not just kind
(05:11):
of understand what's happening with our electronics and everything around us,
but you can actually use some of these weird quantum
effects to do interesting things like microscopes, right, like electric microscopes.
They work on quantum mechanical principles. Yeah. Basically, everything that
works at the very small scale that uses one or
two or small set of particles has to follow quantum rules.
(05:33):
So anything that's been super miniaturized or uses particles to
look at super tiny stuff has to follow quantum rules.
And sometimes those quantum rules are different in a really
useful way. Yeah. And usually this kind of technology is
limited to physics labs and engineering labs and research centers.
But soon quantum mechanics technology might be coming to your home.
(05:55):
That's right, Get ready to buy quantum cookies, I mean
quantum TVs you know, there is actually something quantized by cookies.
You notice how you can't eat one and a half
cookies or three in a quarters cookies. It's always like
into your numbers of cookies. Oh my god, you just
discovered the whites and quantum cookie principle. I did a
(06:17):
lot of experiments. It's more of a social science principle though. Yeah,
it's a bit of a soft science there. Cookies, I
get the software my sciences and your stomach and your
body exactly. Well. There there is now a proposed quantum
television technology and it's based on kind of a and
not a new technology, but a technology that's been around
(06:37):
for a while in quantum mechanics. Yeah, this is really
fascinating idea that lets us build something like artificial atoms
and manipulate electron energy levels to get all sorts of
fascinating properties that we could use for really a wide
range of possible technologies. So to be on the program,
we'll be talking about what are quantum dots? That does
(07:01):
sound like a girl's got a very very small cookie,
the quantum dot. You know, someone what is it? Thin
min's and snickerdoodles and quantum dots? But how many quantum
dots would be in one box of cookies, right, like
ten to twenty six. That's a pretty good deal, mom,
I only had ten of the twelve quantum dot cookies
for dessert. That's your alignment for the rest of your life.
(07:26):
So when you heard the phrase quantum dot, did you
think it was another one of these ridiculous schemes. Yeah,
I'd heard of him before. I just never knew what
they are. I mean, I imagine they're just really small
dots at the quantum level. But you know, is it
like a dot of ink, dot of what? It's a
dot of quantum? Right, pure quantum? All right? Well, as usual,
(07:47):
Daniel went out there into the wild of the Internet
to ask people if they knew what quantum dots are.
So thank you to everyone who broke through their inhibitions
and answered these random questions without any research. If you
would like to participate in the future, please write to
me at questions at Daniel and Jorge dot com. Yes,
I think about it for a second. Is so, when
asked you what a quantum dot is, what would you answer?
(08:10):
Here's what people had to say. I think a quantum
dot refers to a single particle such as an electron
that is isolated by means of electromagnetic fields. The particle
is confined to a small region in space, so it
(08:32):
has a very high um kinetic energy. Okay, I think
quantum dots are really small collections of atoms. Believe often
it's um for gold atoms to lump together. Maybe if
the idea that like the universe is pixelated, maybe quantum
(08:52):
dots are there, the grid points that underly everything. If
I had guess, I would say quantum dots are maybe
something like string theory, where if we break things down
as small as we can get, we're we're stuck with
these quantum dots, and and they can be the building
blocks for a lot of quantum things. I think, or
(09:15):
he said it once. The word quantum just goes in
front of anything these days. It seems like I don't
know for sure, but I think it might refer to
the mathematical concept of a um particle that doesn't have
a volume, so it only has coordinates, but not volume
in space or zero volume. Quantum it's something small and
(09:37):
a dot. It's something small also, so quantum dot. Probably
you'll find it in at the end of a quantum sentence,
how about it. So, I've never actually heard the phrase
quantum dots before. My guess is that it has to
(09:58):
do with the idea of that space itself is quantized,
and that if you were able to zoom in far enough,
there would be a smallest possible point. I've never ever
heard of a quantum dotum afraid. I'm guessing they have
something to do with the idea that space is quantized,
(10:19):
so like pixels on a display. All right, not a
lot of people know what a quantum dot is, apparently no.
But there are some really nice speculations here, like the
math concept of a particle with no volume. That's definitely
something we've talked about in the podcast. I guess everything
is a quantum dot technically, right, like all particles are
just the point particles. Was the difference between a dot
(10:41):
and a point, Daniel get philosophical? One of them has
mint in it, I guess, and the other one doesn't.
I have no idea. I have no idea when it's round,
maybe the other one is pointing. Maybe yeah, I don't know.
A point, technically speaking, is a single value in space,
whereas I guess a dot could have some width to it.
(11:03):
You have a good point that dot. All right, let's
jump into it. Daniel, what is the quantum dot? Settle
this for us? Yeah, quantum dot is really fascinating. It's
basically just a piece of semi conductor, but a very
very very small piece, so you get interesting quantum effects
because semiconductors are sort of very flexible electrically and can
be manipulated by doping and adding different kinds of materials.
(11:26):
You can essentially construct any kind of energy levels you
want for your electron, which is really what determines the
sort of like bulk properties of a material. So it's
just a really really tiny piece of anything, right, doesn't
have you a semiconductor. It can be any material that
you can call it a quantum dot. Yeah, it could
be any material, but we typically use semiconductors because of
(11:46):
their interesting electrical properties. And so take some piece of
material and make a really really small version of it,
and then quantum effects take over. Things like the electron,
for example, gets trapped in your quantum dot, and then
the width of it is now important to how of
that electron behaves. It changes like the energy levels the
electron can have, which changes like how it absorbs light
or a midst light or conducts electricity. How big are
(12:08):
we talking about or how small are we talking about?
These quantum dots being like how many nanometers we're talking
about like one to ten nanometers in size. These are
really tiny, Like you could line up a million of
these things across your finger. They're super duper small, and
they have to be small in order to get to
the quantum effects, right, they have to be basically on
the quantum scale, the Antman scale, so one to ten nanometers.
(12:32):
And how does that compare it to like the you know,
the quote unquote with of an atom. It's about ten
or fifteen times wider than like the hydrogen atom is
defined by like you know, the cloud of electrons around
the nucleus. So you're definitely getting down to that scale.
And I think that's sort of the key idea is
that you know, when you get electrons down to this
really small scale, like the size of a hydrogen atom
(12:54):
or what happens in atoms, they start to exhibit these
quantum properties, like having very specific energy levels that only
happens when you can strain an electron m all right,
So you know it's like maybe ten atoms wide these dots,
and are they actually like dots? Are they like cubes?
Are they like little balls? Do we have pictures of them?
(13:14):
We do have pictures of them. Usually they're little crystals.
And it depends a little bit on how they are
built and how their fabricatum. And we'll get into it
in a minute about how you make these things. And
you can make them in almost any shape. You can
make cubes, you can make pyramids, you can make you know,
diamond shapes, whatever you like. And the shape of the
nanocrystals changes how the electron is sort of capture it
(13:35):
in it and can change its behavior. So depending on
what you want for its electrical properties, you might design
a different shape. M M. All right, So it's almost
like you're kind of making an atom, almost. Yeah. The
key idea here is that when you look at the
periodic table, you see lots of different elements, and those
elements all have really different properties, right, Some of them
conduct a lot of electricity, some of them are really interactive,
(13:56):
and some of them are not. All of those properties
come from behavior of the electrons and their energy levels,
like are those electron orbitals filled? And how big are they? Etcetera, etcetera.
But we're sort of limited to the atoms that we
have in nature. You know, if you want an atom
that does a specific kind of thing that emits light
of a certain frequency or absorbs light of a certain frequency,
you sort of have to pick from the menu that
(14:18):
we have until now. Because quantum dots allow you to
basically engineer electron energy levels to say, I'd like electron
energy levels that look like this, so you can have
whatever whatever property. That's why they're sometimes called artificial atoms.
They don't have a nucleus and electrons around them, but
they have that sort of property of an atom that
they're controlled by their electron energy levels. Interesting, they're like
(14:40):
designer atoms, yes, exactly, designer atoms like made to order. Yeah,
And so if we want a material that does something
that no natural material does, then we can maybe build
it out of quantum dots or design quantum dots that
have that specific ability. What kinds of abilities are we
talking about, like reflecting light or like conduct or how
(15:01):
easy they give off an electron or or how they taste.
I would not recommend eating any of these quantum dots.
Almost all of them are totally toxic. But yeah, they
have interesting optical properties, like they can absorb light at
whatever frequency you want, you know, and they can give
off light at whatever frequencies you want, which is very
helpful for example and making a very crisp display for
(15:22):
your television, and other kinds of things like absorbing power
for solar cells. And there's another aspect to it, which
is maybe less practical but more fascinating, which is that
you can sort of design quantum behaviors. Previously, when people
wanted to do quantum experiments, it was hard because you
had to use like actual atoms that we find in nature,
and those atoms going to be difficult to deal with.
(15:43):
You have to like have a vacuum system and lasers
to capture it. Remember we talked about Bose Einstein contensate.
It's a difficult thing to do because it has to
be done with atoms and all these complex systems. Yeah,
I lose my atoms all the time. They're slippery, they
are slip bury and it's a pain and it's expensive.
But if you could do it with quantum dots, they're
(16:04):
much easier to manufacture. You might even be able to
print them on chips for example, So you could do
all sorts of fascinating quantum experiments without all the expensive machinery.
Could you print like a quantum computer out of quantum dots? Yes, exactly,
that's one direction. People are going trying to build cubits
out of quantum dots. But doesn't the quantum no iss
(16:25):
of something always decrease the more atoms you get, Like
if you have ten atoms, that's usually sort of like
less quantumy than one atom. Right, you can worry about
like decoherence effects. As it interacts with its environment, it
loses some of those quantum effects because the wave functions decohere.
And that's something that's really difficult to do with atoms
because it's hard to isolate them from the system. Right,
(16:46):
The key is isolation. You could have a really large
system that doesn't deco here as long as it remains
isolated from the environment. That's hard to do with atoms
because you know, they bounce around and they jiggle and stuff.
But quantum dots are sort of easier to localize. And
if we're easier to isolate, is the idea, Oh man,
are we going to go back to dot matrix printers,
but this time there will be quantum dot matrix printers. Yeah,
(17:09):
exactly is that? What is that our featured again, and
then we'll go back to quantum motives too, but it
will be the quantum version of those sounds. It would
be much spookier, sound cooler, which is by definition. And
something that's really fascinating about these things is that they're
offering referred to as zero dimensional objects, of course, because
(17:34):
that's not confusing, and that was really confusing for me
when I first was reading about that, because you know,
I'm three dimensional, there's forward, backwards, side to side, and
up and down. I'm defined by three different dimensions, and
you can imagine, you know, a sheet of paper is
almost two dimensional, and like a thin piece of string
is like almost one dimensional. What's a zero dimensional object?
(17:54):
And it's really something where it can't go anywhere, So
it's really like a point in space us. There are
electrons in there, and yes, technically they can move a
little bit sideways, but really they're constrained and the only
way they can move is sort of up and down
in energy. Oh interesting, almost like a perfect box for electrons. Yeah,
it's a perfect little box for electrons. And you know,
quantum mechanically, the way the electron behaves is completely defined
(18:18):
by the shape of the box. Like an electron just
floating through space is not actually quantized like you could
have any energy level. Free electrons are not quantized at all.
The quantization only happens when you constrain it, when you
say you gotta live in this little box or whizz
around this nucleus of the atom. That's where the quantization
comes from. And so here, by constructing your own box,
(18:38):
you define your own energy levels for the electron, which
I think is pretty cool. So we're like quantum designers. Wow,
And this is an idea from the eighties. It was
made a long time ago, but only now maybe we're
getting into how to actually use these thoughts. Yeah, exactly.
The idea has been around for a few decades, and
the proof of principle was done in the eighties. But
(18:58):
with lots of things, it's only really useful if you
can make a lot of them, and if you can
make them at less than like a billion dollars per dot. Right,
All right, well, let's get into how you actually make
a quantum dot and what can you do with them.
But first let's take a quick break. All right, we're
(19:24):
talking about quantum dots, which are not girls cout cookies,
but possibly TVs in the future, yes, TVs, maybe even
in your present. They might end up on our phones. Yeah,
you could have a quantum dots screen. They could create
screens that are like really flexible. You can like a
roll up in the stuff in your pocket. Just don't
eat them. Do not eat quantum screens, all right. Quantum
(19:49):
dot is a little tiny piece of semiconductor, maybe one
to ten nanometers wide, which is about like ten atoms
in with and they can act like little niner atoms.
They can trap electrons and you can make them sit
at whatever energy levels you want. Yeah, you can make
the particles dance whatever dance you tell them to. All right,
(20:09):
So I guess the question is how do you make them?
How do you make a quantum dot? Do you just
like spray some quantumness and they form in the air.
What's the formative? Yeah, it's one teaspoon of quantumness to
teaspoons of dot and then just mix. There you go.
It's hard, right, and this is one of the challenges.
And so there are a lot of different approaches to
making these quantum dots, and we'll see which one sort
(20:30):
of takes off for various applications. There's basically three totally
different approaches. One is chemical, so basically just try to
mix these things like we were just joking about, but
for real. And the idea is that these things are crystals,
which means that in some sense they should self assemble,
you know, the way like crystals will form themselves. If
you put salt into solution and you shake it, the
(20:53):
salt should come out of the solution, you know, make
these crystals. And so you do the same thing with
the kind of quantum dot you want to make. Whatever
it is you're trying to build, maybe it's mostly silicon,
maybe it has other stuff in it. You put all
those ingredients into some solution, you heat it up so
it all like breaks up into a big soup, and
then you hope that nanocrystals get nucleated and then sort
(21:14):
of build on themselves. But then they would be floating
around or they would kind of form on your surface. No,
then they would be floating around exactly, and then you
need to do something to like pull them out and
you know, make them useful somehow. But often you want
them in solution, like maybe you want them suspended in
water so they can glow a certain temperature where you
(21:35):
can inject them into your experiment or whatever. Sounds kind
of tricky. It's pretty tricky, and also it's tricky to
filter them, right. You want only quantum dots that have
formed well, and so this process isn't always going to
form you high quality quantum dots every single time, and
so it's tricky to get exactly the right ones out.
And so people have tried all sorts of variations on
this approach, like using molecular seating, you know, starting with
(22:00):
something that has sort of like the right shape to
nucleate those crystals and encourage things to form just the
right way. It's really complex, sort of like as a
chemistry problem. You know, how do you get all these
molecules bouncing around in solution to come together and like
build themselves out of these mini legos? Right? Yeah, sounds tricky.
What are other ways that you can make them? Another
way is basically following the principles of semiconductor technologies, which
(22:23):
have come really really far in printing tiny circuits. The
way your computer is build is not by super tiny
little fingers soldering together little components individually, right, it's printed
onto a sheet of silk and in a super duper
tiny way. So they have developed this technology because it
underpins the entire consumer electronics and computing industry to print
(22:45):
really really thin layers of semi conductors really near each other.
So they're trying to use and adapt that technology to
also make quantum dots, right, because that technology is they say,
almost running into the physical limits of how what you
can print, right, like the starting to print circuits that
are you know, about this size where the quantum effects
are important, or where you know, you're literally like stacking
(23:07):
ten atoms together. Yeah, they are really approaching the limit
of this technology, which is really awesome and it shows
you like what humans can do, how innovative they can
be when like really pressed to the limit. And also
when there are like billions of dollars at stake, because
the smaller your components, the faster your computer, and so
like Intel and a m D and all these folks
(23:28):
are really really pushing hard on these technologies because there's
literally rivers of money behind it. Yeah, there's a billions
of people who want to phone in their hands and
their pockets, and so the smaller you can get these
chips to the more powerful they are. Yeah, and there's
a lot of examples of when the consumer industry pushes
on something really, really hard, and then it turns out
to be useful for other things like physics research. For example,
(23:50):
that same technology that you use to print circuits, we
also used to print particle detectors at the large Hadron collider.
Those really thin layers of silicon can help you tell, oh,
did an electron pass here, or did a muan pass there,
or was this weird kind of cork that passed through.
So we can print very high resolution detectors for our particles,
and we can never could have developed that technology ourselves.
(24:11):
It's only because billions were spent by the semiconductor industry
to develop that technology. So now people are doing the
same thing for making quantum dots. They're pigging backing on
all those advances, like you can print little quantum dots
on a silicon chip. Yeah, exactly, So this is the
direction that they're going and for making cubits out of
quantum dots, little devices that basically could be the elements
(24:35):
of quantum computers. Currently, the best quantum computers have only
like twenty five maybe fortuits, and they're done using atoms.
But as we talked about previously, having atoms in a trap,
for example, is very unstable. It's very hard to get
that and to keep it isolated and keep it from
deco hearing, which is what you need to do to
do the quantum computing. And so the idea is that
(24:56):
this could be more stable. It's still in its early
days and we don't have a quantum computer made out
of cubits from quantum dots and silicon that competes at
all with the ones made from ions. But you know,
it's a promising avenue. So have they been able to
do it? Have they been able to print quantum dots
using silicon lithography? Yeah, they can print quantum dots. Wow.
So it's like around the corner then, yeah, exactly, it's
(25:17):
around the corner. And you know, there's a bit of
a definitional thing here. Basically, any very small piece of
silicon is a quantum dot. And so in some respects,
anytime you get your silicon that's small, it's a quantum dot.
The question is can you design it to be the
quantum dot you want? Right? Right? I guess technically any
dot is quantum. All dots are quantum. That's right. Even
(25:39):
your girls got cookie crumbs are quantum crumbs if they're
small enough. Yeah, they're there and not there at the
same time, all right, So you can maybe mix them
in solution or print them on a silicon chip. You
can also do something even kind of more interesting. Yeah,
I think the funnest and craziest idea is to use
viruses to assemble these things. What like yeah, like not
(26:03):
the figurative viruses, but real viruses, real actual physical viruses.
So these are things that like attack bacteria and get
the bacteria to make more of themselves. But they can
do more than just reproduce. They actually have like proteins
on their surface that are little molecular machines that can
do stuff. And the idea is that you find a
virus that grabs onto your material, you can use it
(26:23):
as like a little laborer, like a little worker, to
build yourself a crystal out of that material. Wait, so
like viruses can grab and manipulate individual atoms. Yeah, absolutely,
I mean viruses are super small and they have little
proteins on them, right, And what is a protein but
basically a molecular little machine and those proteins have surfaces
on them that buying to some things and not to
(26:45):
other things. Like proteins for example, cut and repair DNA
and DNA is just a string of molecules, and so
we're talking about things at the same scale. And so
the idea is that these viruses, you find ones that
like to grab onto the molecule you want, and you
figure out a way to get the viruses to assemble
in something like a regular pattern. That's the sort of
mind boggling party that the viruses aren't just all like
(27:07):
all swim around, each holding their piece of the quantum dot.
They arrange themselves in something like a crystal pattern. So
then the pieces of the quantum dot there each holding
click together to form the quantum dot. What that's crazy?
Have they actually done? This is is like ongoing research. Yeah,
this is ongoing research. They have actually done it. They
haven't scaled it up, but it's something that really might work.
(27:30):
You know, anytime you can like tap into the power
of biology. We could never engineer something ourselves that way.
But the way they take advantage of it is through evolution.
They do this thing called phage display where they put
a bunch of the material they want the viruses to
capture on a surface, and then they just wash viruses
over it, and the ones that grab onto the surface
are the ones they keep. And then they breathe those
(27:51):
viruses together to make new viruses, and they do it
again and again and again, and so they're like artificially
selecting viruses that are good at this one. So basically
breeding little viruses that can do our jobs for us. Wow,
I mean, we all know how good we are at
handling viruses. It does seem as a civilization, what could
go wrong, Daniel, What could go wrong? Exactly? Maybe they
(28:17):
could bake our cookies for us. That's pretty interesting that
you can maybe like kind of use viruses as little
assembly robots. Yeah, little nano robots. I mean, rather than
going to our engineers and saying, hey, could you build
me a super tinier robot that's nanometers wide and can
do this job, just find one out there in nature
and adapt it to your purpose. Al Right, Well, it
(28:38):
sounds like you can build quantum dots. I guess is
the hard part is getting them to do the things
you want them to do, or to like, you know,
design them and make them to spect to take advantage
of these interesting quantum properties. Yeah, if you want the
quantum properties to do exactly what you want, you have
to design them just right. You need exactly the right
kind of you know, gallium in their academy um in
(29:00):
there to get just the kind of electron energy levels
you need to accomplish what you're trying to accomplish. All right, well,
let's get into what quantum dots can do. What can
they do for you, Daniel? Besides you know, entertain enemies
or give you taste your cookies and maybe raise a
virus army to take over the world to make more cookies.
(29:22):
Oh yeah, that's what I meant. That's what I meant.
Or take over the world with cookies. You know, there's
always a way. But for us, let's take a quick break.
All right, quantum dots are gonna take over the world, Daniel.
(29:44):
They're gonna improve our screen technology apparently, and maybe a
lot more because basically you can make quantum computers, or
you can kind of make designer atoms so that you
can make things maybe that has special properties. Yeah, So
what are some of the things that them dots can do? Well,
the most important thing is that quantum dots can have
sort of designer optical properties. Remember that the reason that
(30:06):
some things look a certain color is because they reflect
light of that color, which means they're absorbing all the
other colors. So if you can design a material that
absorbs light at certain frequencies and other frequencies, you can
basically design its color to be whatever you like. And
if you want to design a very crisp display or
you want to marker, you can inject into your experimental
(30:27):
subject and watch as something flows around. Then you want
to be able to design its optical properties. And so
as you change the size of your quantum dot, for example,
you change the energy that that electron can absorb, which
changes how it looks optically. It's kind of sounds like
you're just making colors, though, Like isn't that how color works? Usually,
(30:49):
like the atom in like a blue paint reflect blue
light especially. Yeah, that's exactly what we're trying to do.
We're just making colors, but we're making very crisp, well
the fine colors, right. You want something which absorbs very
very narrowly or only reflects a very very narrow range
of frequencies. So it's like exactly blue or super duper
(31:10):
perfect red or exactly the green you were looking for.
I see quantum paint is the new marketing term. Yeah, exactly.
And so this makes it if you're going to build
a television, for example, it makes it much easier to
get crisp colors. You know exactly how to combine your
various little layers to get exactly the color you want
(31:32):
on screen. So it's simpler, it's cheaper, it's more efficient.
You don't need, like, you know, complicated filters to get
rid of the edge effects that you didn't really want
because you were forced to use the atoms that physics
gave you. You You can invent your own atoms to devise
your own quantum screen. But can you make these quantum
dots change the light or turn them on and off?
How would this work? How would this television work? Would
(31:53):
it be just a one image television? I think each
one is essentially like a filter. So you put some
source of light behind a layer of red quantum dots,
and which you get our red light. Or if you
put light behind the layer of green condom dots, you
get green light or blue light. So it operates on
the same basic principle as all your other televisions, which
(32:16):
have for example blue LEDs or green l e d
s or red l e d s. But this is
the way that you get the pure light instead of
all the white light. Be like super precise colors. That's
the idea. Super precise colors. Yeah, extra precise, extra precise.
And also because they're more efficient they show exactly the
color you want, there's lower energy consumption and so you
(32:38):
can have like longer lifetimes. And that's the turkey part,
I guess is how you make them at the size
of a television because you have to make a lot
of them. You've got to make a lot of them
yet exactly, and they have to survive my kids dropping
my phone for example. They do. But you know, because
they can be sort of printed on anything in their
microscopic they can potentially be you for things like you know,
(33:01):
rollable or flexible displays in the future, all right, or
like a like a blanket TV, yeah, or TV you
could like fold up and you know, stick in your
pocket or something. Alright. What else can we use quantum
dots for? Another awesome application is in solar cells, because
again you can really tune the absorption and the emission
(33:23):
then you can get quantum dots that absorb light at
exactly the peak wavelength that you're seeing on your roof,
you know, so you can make sure that like the
peak efficiency for absorption is where most of the light
actually is, right because right now it's kind of fuzzy, right, Yeah, exactly,
it's kind of fuzzy. And these solar cells are expensive
to produce. But if you could get quantum dots ramped
(33:44):
up so you can make a lot of them, you
can make basically like solar power paint, and you could
like have a solution with quantum dots in it that
you basically paint onto a surface and it becomes a
solar power cell. What Like, you can just paint your
roof and then attach some wires to it and it's
a solar panel. Yes exactly, that is wild. Yeah, they
would absorb the energy and they would like chain themselves
(34:06):
up so they can pass a current along and so
that would be pretty awesome. Like, you know how cool
it is that you can paint like a chalkboard on
a wall and it actually kind of works. That's pretty cool. Well,
this is like a step beyond that. It's like painting
an electrical device onto your roof or anything, really your
car or your hat or really you're you can get
a tattoo. Can you get a solar cell tattoo, you know,
(34:29):
inked on your skin? It would be awesome, and you
can charge your phone just by against your body. Yeah,
and the tattoo should look like a solar cell, and right,
that would be super cool. It looks like a solar
cell and acts like a solar cell. Well, technically you
could make it look like anything. Yeah, you could. You
can make it look like a rose or your grandma,
(34:49):
and it would be helping you save some energy, would
be cool? It power your phone? Yeah cool? All right,
so you can make solar paint. What else can you
do with it? You can also use it in science.
A lot of biology uses something called bio labeling, where
you like inject some substance into a bacterium or into
a larger animal, and you want to follow, like where
did it go? Where is it being used? Where is
(35:10):
the active site where it's like being actually processed. So
these quantum dots are like more stable and brighter than
most of the other dies, and so they're much more useful.
They can like last for months, but they're also toxicing,
aren't they. Yes, they're poisonous. I guess if you don't
want your sample to live very long. Yeah, a lot
of them. Because you want to engineer particular optical properties
(35:32):
require you to use various substances like cadmium, which is
pretty toxic. So we're not at a point where you
want to You know, your kids eating a spoonful of
quantum dots are definitely not. But you know, if you
don't mind killing your bacteria to learn about how it's
doing something or how it's defending itself, then it's all right.
Does that put a kaboche on the tattoos as well?
(35:53):
If you tattoos cadmium into your body, that would give
you other kinds of cancer. Yes, not recommended. Yet, people
are working on ways to make quantum dots that don't
require a cadmium or other toxic materials, so I'm pretty
sure that in the future will have humans safe quantum dots. Alright, cool,
What else can we make with quantum dots? Well, we
(36:13):
can also build super tiny electronics. You know about this
material called graphine, which is basically like a lattice of
carbon built in a super fancy interesting way that has
fancy molecular properties. Well, graphing is really stable and really
conductive even when it's cut into super tiny devices like
one nanometer wide. And so you can build like the
(36:35):
tiniest of electronics using graphing single crystals, which are technically
also quantum dots that you can make a circuit that's
literally like one atom talks to another atom, and then
that atom talks to another atom. Yeah, exactly, And so
this is like one potential way to even further miniaturize
our electronics. But wouldn't it get quantum at that point
(36:57):
or like, would it still behave like a regular circuit.
It would get want them exactly, but so you have
to define it to do exactly what you want. But
you can build transistors out of single atoms, and single
electron transistors are a thing you can do. The chemistry
and the physics is a little bit different from the
way we're currently doing electronics, but you can build the
basic components we need for circuits out of these graphing
(37:18):
single crystals. All right, Well, but it sounds like maybe
the technology that's pushing it at least into the mainstream
is this idea of a quantum TV. So how far
away are we from that? Are they actually starting to
make them or think about them or Netflix investing on this. Yeah,
quantum TVs are negative five years away, which means they've
(37:39):
been on the market since about What what do you mean,
like you can put in money to buy a quantum
TV ten years in the future. No, that means five
years ago, if you went on Amazon and typed in
quantum l e ED there were TVs for sale that
you could purchase. You could go purchase a quantum l
a ED TV right now. But it's not really made
out of quantum dots, is it. No, it really has
(38:00):
quantum dot technology. Oh, this is really a thing. Really wow, Okay,
it's not a future technology. It's like five years ago technology.
It's like Obama years technology. Exactly. Obama probably has a
quantum TV and he's probably sitting in front of it
eating quantum cookies right now, because yes, we can watch
(38:21):
a quantum TV. Really, So if I buy a quantum TV,
it has like quantum dots in it, Yeah, exactly, it
has a quantum dot layer which filters this like led
backlight and helps reduce better color. So, like we were
saying at the top of the program. Quantum TVs are
not a scam. They are real and they actually use
quantum technology. Unlike quantum yogurt and quantum hamsters and quantum
(38:43):
massage and quantum stealth technology. This is real applications of
quantum mechanics on your wall right right. Although you know,
technically yogurt does have quantum particles in it. Everything tastes
like particles. In the end, it's just a good figure
and gut. All right. So have you seen a quantum TV?
Does it look crisper and does it look nicer? I
(39:04):
think you should do some research and you'll maybe buy
yourself a TV with your grant money. Yeah, maybe I will.
You know, I did look up quantum TVs, but I
can only watch a video of a quantum TV on
my non quantum screen, and so it doesn't really come through.
It's like looking at a video of a high definition
television on your low definition television. It's not very impressive.
(39:24):
So I've never actually seen one. And also the only
clip you can watch is a clip of vaculating quantum leap,
which doesn't help you. Yeah, they need to work on
the quantum content, really, but no, I've never actually seen
one in the wild. So any listeners out there that
have a quantum screen right to us and let us
know how awesome is it. Yeah, take a picture and
send it to us to see how good it looks.
(39:46):
Take a quantum picture. Yeah, we'll get it and not
get it at the same time. All right, Well, um,
that's pretty cool that this technology is out there. It
is being used on televisions. People are technically potentially watching
Netflix right now with the quantum TV, I hope. So
all right, and it might potentially give some pretty amazing
technologies in the future. That's right. With the power to
(40:09):
understand the quantum world comes the ability to engineer it
and have it do all sorts of things that normal
atoms cannot do. So it's not just that physics is
playing with the universe because we want to understand, but
sometimes there are actual benefits for humanity. Yeah, yeah, stay
tuned for those quantum tattoos. Will every physicist get one?
Just do like, you know, show solidarity and team spirit.
(40:33):
I don't think you could ever say every physicist will
do anything apply for grants. All right, Well, we hope
you enjoyed that, and we hope you look at the
world a little bit different. Sometimes, quantum technology and quantum
effects are there for us to see and for us
to bench watch with. Well, thanks for joining us, See
you next time. Thanks for listening, and remember that Daniel
(41:02):
and Jorge Explain the Universe is a production of I
Heart Radio. For more podcast for my Heart Radio, visit
the I Heart Radio Apple Apple Podcasts, or wherever you
listen to your favorite shows. Ye
Hey, Daniel, I found another physics related scam recently. Oh
did someone try to sell you quantum girl scott cookies? Again?
Girls cut cookies do seem to quantum tunnel into my
stomach pretty easily. I don't even have to eat him.
So then, what's the scam? I saw an ad for
a quantum television? Can you believe that? Nonsense? Actually? Wait,
(00:31):
what do you mean? This is the real thing? What
does the quantum TV do? Is it always fuzzy because
of the uncertainty principle? Yeah, you know, the word quantum
gets abused a lot, but this one time it's for real.
It's not a scam. No, quantum televisions are a real thing,
and they are extra crispy, just like a girl's Scout cookie.
(01:08):
I am or Hammaye, cartoonists and the creator of PhD comics. Hi,
I'm Daniel. I'm a particle of physicists, and I'm at
least made out of girls Scout cookies. Oh wow, you're
you're a big fan. It's for a good cause, you know,
that's why I eat them. It's for a good cause.
You know you can buy them and not eat them.
What that would be offensive? You have to throw them
(01:29):
in the trash, and you don't have to tell the
girls cuts they would know. But welcome to our podcast.
Daniel and Jorge Explain the Universe April, that kind of
irt radio in which we take our cookie fueled brains
and try to understand everything about the universe, not just
the tiny quantum particles and the crazy stuff happening in
the center of stars, but everything in between. We take
(01:53):
that immense mental journey all the way out into the
universe and back into the quantum particles and explain all
of it to you. Yeah, do you have a favorite
girl Scout cookies? Daniel? Oh, we're getting real here, huh.
I'm not gonna endorse one particular Girls Scott Cookies. I
gotta go. I think with the classic than mint. You know,
It's just it's so easy for them to tunnel into
your stomach. My spouse would be appalled at the mixing
(02:15):
of mint and chocolate. Do this taste like toothpaste to her? Yeah?
With chocolate. There's probably a reason there's no chocolate toothpaste flavor.
But there are a lot of interesting and amazing things
in this universe that we like to talk about in
this podcast. Things that are out there in the vast
reaches of space, and also things that are right here
(02:37):
at home, and things that are maybe at the tip
of your fingertip without even knowing. Yes, things that are
harder to understand even then, the combination of herbs and chocolate,
things that are weird, things that are quantum, things that
make no sense but are actually real. Yeah, because physics
reveals that the universe is a pretty weird place. It
(02:58):
doesn't always work the same way that we grew up
thinking that it worked. There's all kinds of strange things
going on, especially at the microscopic and at the quantum level. Yeah,
that's basically the job of physics is to figure out
how does the world actually work, Not the way we
thought it should work, or the way we might have
imagined it worked from our experience with rivers and rocks
(03:19):
and stuff, but the way fundamentally things actually happen. And
sometimes that's just for our edification, just to know how
the universe actually works. But sometimes it's actually useful and
we can use it to build cool new stuff. Wait,
what physics can be useful? Who told you that? Some
physicists your parents, some physicist After he told me some cookies.
(03:44):
Oh right, right, a limit or professional limit to being
a girl scout. You've never had a physics scott cookie?
Does it taste like particles? I hear the Higgs boson
is pretty tasty. Everything tastes like particles, man, everything particles.
Particles are also the only things doing any tasting. Yeah,
you're saying that physics can be useful. Physics can be useful. Yes.
(04:08):
In fact, you know, the Worldwide Web was invented at
a particle physics laboratory, and all sorts of things come
out of just like gaining knowledge about how the universe works, right,
And we all know how useful the Worldwide Web is.
That's right. It's contributed to a huge decrease in productivity worldwide.
It's like an anti useful particle there, depends on your
(04:29):
goals man of reducing work. But yeah, well I do
admit this useful to know physics, for sure, and sometimes
we can use that knowledge to build amazing and and
cool things that we couldn't do before. And that includes
maybe quantum mechanics, which is like the weirdest and most
awesomest thing in the universe. It is, and our understanding
(04:50):
quantum mechanics underlies most modern electronics. It's the reason that
your phone works, it's the reason your computer boots up.
It's also the reason your computer crashes. I guess no,
that's the fault of the girls got cookie crumples that
fell in my keywork. It's like a physical virus infecting
your computer. Yeah, quantum mechanics helps us not just kind
(05:11):
of understand what's happening with our electronics and everything around us,
but you can actually use some of these weird quantum
effects to do interesting things like microscopes, right, like electric microscopes.
They work on quantum mechanical principles. Yeah. Basically, everything that
works at the very small scale that uses one or
two or small set of particles has to follow quantum rules.
(05:33):
So anything that's been super miniaturized or uses particles to
look at super tiny stuff has to follow quantum rules.
And sometimes those quantum rules are different in a really
useful way. Yeah. And usually this kind of technology is
limited to physics labs and engineering labs and research centers.
But soon quantum mechanics technology might be coming to your home.
(05:55):
That's right, Get ready to buy quantum cookies, I mean
quantum TVs you know, there is actually something quantized by cookies.
You notice how you can't eat one and a half
cookies or three in a quarters cookies. It's always like
into your numbers of cookies. Oh my god, you just
discovered the whites and quantum cookie principle. I did a
(06:17):
lot of experiments. It's more of a social science principle though. Yeah,
it's a bit of a soft science there. Cookies, I
get the software my sciences and your stomach and your
body exactly. Well. There there is now a proposed quantum
television technology and it's based on kind of a and
not a new technology, but a technology that's been around
(06:37):
for a while in quantum mechanics. Yeah, this is really
fascinating idea that lets us build something like artificial atoms
and manipulate electron energy levels to get all sorts of
fascinating properties that we could use for really a wide
range of possible technologies. So to be on the program,
we'll be talking about what are quantum dots? That does
(07:01):
sound like a girl's got a very very small cookie,
the quantum dot. You know, someone what is it? Thin
min's and snickerdoodles and quantum dots? But how many quantum
dots would be in one box of cookies, right, like
ten to twenty six. That's a pretty good deal, mom,
I only had ten of the twelve quantum dot cookies
for dessert. That's your alignment for the rest of your life.
(07:26):
So when you heard the phrase quantum dot, did you
think it was another one of these ridiculous schemes. Yeah,
I'd heard of him before. I just never knew what
they are. I mean, I imagine they're just really small
dots at the quantum level. But you know, is it
like a dot of ink, dot of what? It's a
dot of quantum? Right, pure quantum? All right? Well, as usual,
(07:47):
Daniel went out there into the wild of the Internet
to ask people if they knew what quantum dots are.
So thank you to everyone who broke through their inhibitions
and answered these random questions without any research. If you
would like to participate in the future, please write to
me at questions at Daniel and Jorge dot com. Yes,
I think about it for a second. Is so, when
asked you what a quantum dot is, what would you answer?
(08:10):
Here's what people had to say. I think a quantum
dot refers to a single particle such as an electron
that is isolated by means of electromagnetic fields. The particle
is confined to a small region in space, so it
(08:32):
has a very high um kinetic energy. Okay, I think
quantum dots are really small collections of atoms. Believe often
it's um for gold atoms to lump together. Maybe if
the idea that like the universe is pixelated, maybe quantum
(08:52):
dots are there, the grid points that underly everything. If
I had guess, I would say quantum dots are maybe
something like string theory, where if we break things down
as small as we can get, we're we're stuck with
these quantum dots, and and they can be the building
blocks for a lot of quantum things. I think, or
(09:15):
he said it once. The word quantum just goes in
front of anything these days. It seems like I don't
know for sure, but I think it might refer to
the mathematical concept of a um particle that doesn't have
a volume, so it only has coordinates, but not volume
in space or zero volume. Quantum it's something small and
(09:37):
a dot. It's something small also, so quantum dot. Probably
you'll find it in at the end of a quantum sentence,
how about it. So, I've never actually heard the phrase
quantum dots before. My guess is that it has to
(09:58):
do with the idea of that space itself is quantized,
and that if you were able to zoom in far enough,
there would be a smallest possible point. I've never ever
heard of a quantum dotum afraid. I'm guessing they have
something to do with the idea that space is quantized,
(10:19):
so like pixels on a display. All right, not a
lot of people know what a quantum dot is, apparently no.
But there are some really nice speculations here, like the
math concept of a particle with no volume. That's definitely
something we've talked about in the podcast. I guess everything
is a quantum dot technically, right, like all particles are
just the point particles. Was the difference between a dot
(10:41):
and a point, Daniel get philosophical? One of them has
mint in it, I guess, and the other one doesn't.
I have no idea. I have no idea when it's round,
maybe the other one is pointing. Maybe yeah, I don't know.
A point, technically speaking, is a single value in space,
whereas I guess a dot could have some width to it.
(11:03):
You have a good point that dot. All right, let's
jump into it. Daniel, what is the quantum dot? Settle
this for us? Yeah, quantum dot is really fascinating. It's
basically just a piece of semi conductor, but a very
very very small piece, so you get interesting quantum effects
because semiconductors are sort of very flexible electrically and can
be manipulated by doping and adding different kinds of materials.
(11:26):
You can essentially construct any kind of energy levels you
want for your electron, which is really what determines the
sort of like bulk properties of a material. So it's
just a really really tiny piece of anything, right, doesn't
have you a semiconductor. It can be any material that
you can call it a quantum dot. Yeah, it could
be any material, but we typically use semiconductors because of
(11:46):
their interesting electrical properties. And so take some piece of
material and make a really really small version of it,
and then quantum effects take over. Things like the electron,
for example, gets trapped in your quantum dot, and then
the width of it is now important to how of
that electron behaves. It changes like the energy levels the
electron can have, which changes like how it absorbs light
or a midst light or conducts electricity. How big are
(12:08):
we talking about or how small are we talking about?
These quantum dots being like how many nanometers we're talking
about like one to ten nanometers in size. These are
really tiny, Like you could line up a million of
these things across your finger. They're super duper small, and
they have to be small in order to get to
the quantum effects, right, they have to be basically on
the quantum scale, the Antman scale, so one to ten nanometers.
(12:32):
And how does that compare it to like the you know,
the quote unquote with of an atom. It's about ten
or fifteen times wider than like the hydrogen atom is
defined by like you know, the cloud of electrons around
the nucleus. So you're definitely getting down to that scale.
And I think that's sort of the key idea is
that you know, when you get electrons down to this
really small scale, like the size of a hydrogen atom
(12:54):
or what happens in atoms, they start to exhibit these
quantum properties, like having very specific energy levels that only
happens when you can strain an electron m all right,
So you know it's like maybe ten atoms wide these dots,
and are they actually like dots? Are they like cubes?
Are they like little balls? Do we have pictures of them?
(13:14):
We do have pictures of them. Usually they're little crystals.
And it depends a little bit on how they are
built and how their fabricatum. And we'll get into it
in a minute about how you make these things. And
you can make them in almost any shape. You can
make cubes, you can make pyramids, you can make you know,
diamond shapes, whatever you like. And the shape of the
nanocrystals changes how the electron is sort of capture it
(13:35):
in it and can change its behavior. So depending on
what you want for its electrical properties, you might design
a different shape. M M. All right, So it's almost
like you're kind of making an atom, almost. Yeah. The
key idea here is that when you look at the
periodic table, you see lots of different elements, and those
elements all have really different properties, right, Some of them
conduct a lot of electricity, some of them are really interactive,
(13:56):
and some of them are not. All of those properties
come from behavior of the electrons and their energy levels,
like are those electron orbitals filled? And how big are they? Etcetera, etcetera.
But we're sort of limited to the atoms that we
have in nature. You know, if you want an atom
that does a specific kind of thing that emits light
of a certain frequency or absorbs light of a certain frequency,
you sort of have to pick from the menu that
(14:18):
we have until now. Because quantum dots allow you to
basically engineer electron energy levels to say, I'd like electron
energy levels that look like this, so you can have
whatever whatever property. That's why they're sometimes called artificial atoms.
They don't have a nucleus and electrons around them, but
they have that sort of property of an atom that
they're controlled by their electron energy levels. Interesting, they're like
(14:40):
designer atoms, yes, exactly, designer atoms like made to order. Yeah,
And so if we want a material that does something
that no natural material does, then we can maybe build
it out of quantum dots or design quantum dots that
have that specific ability. What kinds of abilities are we
talking about, like reflecting light or like conduct or how
(15:01):
easy they give off an electron or or how they taste.
I would not recommend eating any of these quantum dots.
Almost all of them are totally toxic. But yeah, they
have interesting optical properties, like they can absorb light at
whatever frequency you want, you know, and they can give
off light at whatever frequencies you want, which is very
helpful for example and making a very crisp display for
(15:22):
your television, and other kinds of things like absorbing power
for solar cells. And there's another aspect to it, which
is maybe less practical but more fascinating, which is that
you can sort of design quantum behaviors. Previously, when people
wanted to do quantum experiments, it was hard because you
had to use like actual atoms that we find in nature,
and those atoms going to be difficult to deal with.
(15:43):
You have to like have a vacuum system and lasers
to capture it. Remember we talked about Bose Einstein contensate.
It's a difficult thing to do because it has to
be done with atoms and all these complex systems. Yeah,
I lose my atoms all the time. They're slippery, they
are slip bury and it's a pain and it's expensive.
But if you could do it with quantum dots, they're
(16:04):
much easier to manufacture. You might even be able to
print them on chips for example, So you could do
all sorts of fascinating quantum experiments without all the expensive machinery.
Could you print like a quantum computer out of quantum dots? Yes, exactly,
that's one direction. People are going trying to build cubits
out of quantum dots. But doesn't the quantum no iss
(16:25):
of something always decrease the more atoms you get, Like
if you have ten atoms, that's usually sort of like
less quantumy than one atom. Right, you can worry about
like decoherence effects. As it interacts with its environment, it
loses some of those quantum effects because the wave functions decohere.
And that's something that's really difficult to do with atoms
because it's hard to isolate them from the system. Right,
(16:46):
The key is isolation. You could have a really large
system that doesn't deco here as long as it remains
isolated from the environment. That's hard to do with atoms
because you know, they bounce around and they jiggle and stuff.
But quantum dots are sort of easier to localize. And
if we're easier to isolate, is the idea, Oh man,
are we going to go back to dot matrix printers,
but this time there will be quantum dot matrix printers. Yeah,
(17:09):
exactly is that? What is that our featured again, and
then we'll go back to quantum motives too, but it
will be the quantum version of those sounds. It would
be much spookier, sound cooler, which is by definition. And
something that's really fascinating about these things is that they're
offering referred to as zero dimensional objects, of course, because
(17:34):
that's not confusing, and that was really confusing for me
when I first was reading about that, because you know,
I'm three dimensional, there's forward, backwards, side to side, and
up and down. I'm defined by three different dimensions, and
you can imagine, you know, a sheet of paper is
almost two dimensional, and like a thin piece of string
is like almost one dimensional. What's a zero dimensional object?
(17:54):
And it's really something where it can't go anywhere, So
it's really like a point in space us. There are
electrons in there, and yes, technically they can move a
little bit sideways, but really they're constrained and the only
way they can move is sort of up and down
in energy. Oh interesting, almost like a perfect box for electrons. Yeah,
it's a perfect little box for electrons. And you know,
quantum mechanically, the way the electron behaves is completely defined
(18:18):
by the shape of the box. Like an electron just
floating through space is not actually quantized like you could
have any energy level. Free electrons are not quantized at all.
The quantization only happens when you constrain it, when you
say you gotta live in this little box or whizz
around this nucleus of the atom. That's where the quantization
comes from. And so here, by constructing your own box,
(18:38):
you define your own energy levels for the electron, which
I think is pretty cool. So we're like quantum designers. Wow,
And this is an idea from the eighties. It was
made a long time ago, but only now maybe we're
getting into how to actually use these thoughts. Yeah, exactly.
The idea has been around for a few decades, and
the proof of principle was done in the eighties. But
(18:58):
with lots of things, it's only really useful if you
can make a lot of them, and if you can
make them at less than like a billion dollars per dot. Right,
All right, well, let's get into how you actually make
a quantum dot and what can you do with them.
But first let's take a quick break. All right, we're
(19:24):
talking about quantum dots, which are not girls cout cookies,
but possibly TVs in the future, yes, TVs, maybe even
in your present. They might end up on our phones. Yeah,
you could have a quantum dots screen. They could create
screens that are like really flexible. You can like a
roll up in the stuff in your pocket. Just don't
eat them. Do not eat quantum screens, all right. Quantum
(19:49):
dot is a little tiny piece of semiconductor, maybe one
to ten nanometers wide, which is about like ten atoms
in with and they can act like little niner atoms.
They can trap electrons and you can make them sit
at whatever energy levels you want. Yeah, you can make
the particles dance whatever dance you tell them to. All right,
(20:09):
So I guess the question is how do you make them?
How do you make a quantum dot? Do you just
like spray some quantumness and they form in the air.
What's the formative? Yeah, it's one teaspoon of quantumness to
teaspoons of dot and then just mix. There you go.
It's hard, right, and this is one of the challenges.
And so there are a lot of different approaches to
making these quantum dots, and we'll see which one sort
(20:30):
of takes off for various applications. There's basically three totally
different approaches. One is chemical, so basically just try to
mix these things like we were just joking about, but
for real. And the idea is that these things are crystals,
which means that in some sense they should self assemble,
you know, the way like crystals will form themselves. If
you put salt into solution and you shake it, the
(20:53):
salt should come out of the solution, you know, make
these crystals. And so you do the same thing with
the kind of quantum dot you want to make. Whatever
it is you're trying to build, maybe it's mostly silicon,
maybe it has other stuff in it. You put all
those ingredients into some solution, you heat it up so
it all like breaks up into a big soup, and
then you hope that nanocrystals get nucleated and then sort
(21:14):
of build on themselves. But then they would be floating
around or they would kind of form on your surface. No,
then they would be floating around exactly, and then you
need to do something to like pull them out and
you know, make them useful somehow. But often you want
them in solution, like maybe you want them suspended in
water so they can glow a certain temperature where you
(21:35):
can inject them into your experiment or whatever. Sounds kind
of tricky. It's pretty tricky, and also it's tricky to
filter them, right. You want only quantum dots that have
formed well, and so this process isn't always going to
form you high quality quantum dots every single time, and
so it's tricky to get exactly the right ones out.
And so people have tried all sorts of variations on
this approach, like using molecular seating, you know, starting with
(22:00):
something that has sort of like the right shape to
nucleate those crystals and encourage things to form just the
right way. It's really complex, sort of like as a
chemistry problem. You know, how do you get all these
molecules bouncing around in solution to come together and like
build themselves out of these mini legos? Right? Yeah, sounds tricky.
What are other ways that you can make them? Another
way is basically following the principles of semiconductor technologies, which
(22:23):
have come really really far in printing tiny circuits. The
way your computer is build is not by super tiny
little fingers soldering together little components individually, right, it's printed
onto a sheet of silk and in a super duper
tiny way. So they have developed this technology because it
underpins the entire consumer electronics and computing industry to print
(22:45):
really really thin layers of semi conductors really near each other.
So they're trying to use and adapt that technology to
also make quantum dots, right, because that technology is they say,
almost running into the physical limits of how what you
can print, right, like the starting to print circuits that
are you know, about this size where the quantum effects
are important, or where you know, you're literally like stacking
(23:07):
ten atoms together. Yeah, they are really approaching the limit
of this technology, which is really awesome and it shows
you like what humans can do, how innovative they can
be when like really pressed to the limit. And also
when there are like billions of dollars at stake, because
the smaller your components, the faster your computer, and so
like Intel and a m D and all these folks
(23:28):
are really really pushing hard on these technologies because there's
literally rivers of money behind it. Yeah, there's a billions
of people who want to phone in their hands and
their pockets, and so the smaller you can get these
chips to the more powerful they are. Yeah, and there's
a lot of examples of when the consumer industry pushes
on something really, really hard, and then it turns out
to be useful for other things like physics research. For example,
(23:50):
that same technology that you use to print circuits, we
also used to print particle detectors at the large Hadron collider.
Those really thin layers of silicon can help you tell, oh,
did an electron pass here, or did a muan pass there,
or was this weird kind of cork that passed through.
So we can print very high resolution detectors for our particles,
and we can never could have developed that technology ourselves.
(24:11):
It's only because billions were spent by the semiconductor industry
to develop that technology. So now people are doing the
same thing for making quantum dots. They're pigging backing on
all those advances, like you can print little quantum dots
on a silicon chip. Yeah, exactly, So this is the
direction that they're going and for making cubits out of
quantum dots, little devices that basically could be the elements
(24:35):
of quantum computers. Currently, the best quantum computers have only
like twenty five maybe fortuits, and they're done using atoms.
But as we talked about previously, having atoms in a trap,
for example, is very unstable. It's very hard to get
that and to keep it isolated and keep it from
deco hearing, which is what you need to do to
do the quantum computing. And so the idea is that
(24:56):
this could be more stable. It's still in its early
days and we don't have a quantum computer made out
of cubits from quantum dots and silicon that competes at
all with the ones made from ions. But you know,
it's a promising avenue. So have they been able to
do it? Have they been able to print quantum dots
using silicon lithography? Yeah, they can print quantum dots. Wow.
So it's like around the corner then, yeah, exactly, it's
(25:17):
around the corner. And you know, there's a bit of
a definitional thing here. Basically, any very small piece of
silicon is a quantum dot. And so in some respects,
anytime you get your silicon that's small, it's a quantum dot.
The question is can you design it to be the
quantum dot you want? Right? Right? I guess technically any
dot is quantum. All dots are quantum. That's right. Even
(25:39):
your girls got cookie crumbs are quantum crumbs if they're
small enough. Yeah, they're there and not there at the
same time, all right, So you can maybe mix them
in solution or print them on a silicon chip. You
can also do something even kind of more interesting. Yeah,
I think the funnest and craziest idea is to use
viruses to assemble these things. What like yeah, like not
(26:03):
the figurative viruses, but real viruses, real actual physical viruses.
So these are things that like attack bacteria and get
the bacteria to make more of themselves. But they can
do more than just reproduce. They actually have like proteins
on their surface that are little molecular machines that can
do stuff. And the idea is that you find a
virus that grabs onto your material, you can use it
(26:23):
as like a little laborer, like a little worker, to
build yourself a crystal out of that material. Wait, so
like viruses can grab and manipulate individual atoms. Yeah, absolutely,
I mean viruses are super small and they have little
proteins on them, right, And what is a protein but
basically a molecular little machine and those proteins have surfaces
on them that buying to some things and not to
(26:45):
other things. Like proteins for example, cut and repair DNA
and DNA is just a string of molecules, and so
we're talking about things at the same scale. And so
the idea is that these viruses, you find ones that
like to grab onto the molecule you want, and you
figure out a way to get the viruses to assemble
in something like a regular pattern. That's the sort of
mind boggling party that the viruses aren't just all like
(27:07):
all swim around, each holding their piece of the quantum dot.
They arrange themselves in something like a crystal pattern. So
then the pieces of the quantum dot there each holding
click together to form the quantum dot. What that's crazy?
Have they actually done? This is is like ongoing research. Yeah,
this is ongoing research. They have actually done it. They
haven't scaled it up, but it's something that really might work.
(27:30):
You know, anytime you can like tap into the power
of biology. We could never engineer something ourselves that way.
But the way they take advantage of it is through evolution.
They do this thing called phage display where they put
a bunch of the material they want the viruses to
capture on a surface, and then they just wash viruses
over it, and the ones that grab onto the surface
are the ones they keep. And then they breathe those
(27:51):
viruses together to make new viruses, and they do it
again and again and again, and so they're like artificially
selecting viruses that are good at this one. So basically
breeding little viruses that can do our jobs for us. Wow,
I mean, we all know how good we are at
handling viruses. It does seem as a civilization, what could
go wrong, Daniel, What could go wrong? Exactly? Maybe they
(28:17):
could bake our cookies for us. That's pretty interesting that
you can maybe like kind of use viruses as little
assembly robots. Yeah, little nano robots. I mean, rather than
going to our engineers and saying, hey, could you build
me a super tinier robot that's nanometers wide and can
do this job, just find one out there in nature
and adapt it to your purpose. Al Right, Well, it
(28:38):
sounds like you can build quantum dots. I guess is
the hard part is getting them to do the things
you want them to do, or to like, you know,
design them and make them to spect to take advantage
of these interesting quantum properties. Yeah, if you want the
quantum properties to do exactly what you want, you have
to design them just right. You need exactly the right
kind of you know, gallium in their academy um in
(29:00):
there to get just the kind of electron energy levels
you need to accomplish what you're trying to accomplish. All right, well,
let's get into what quantum dots can do. What can
they do for you, Daniel? Besides you know, entertain enemies
or give you taste your cookies and maybe raise a
virus army to take over the world to make more cookies.
(29:22):
Oh yeah, that's what I meant. That's what I meant.
Or take over the world with cookies. You know, there's
always a way. But for us, let's take a quick break.
All right, quantum dots are gonna take over the world, Daniel.
(29:44):
They're gonna improve our screen technology apparently, and maybe a
lot more because basically you can make quantum computers, or
you can kind of make designer atoms so that you
can make things maybe that has special properties. Yeah, So
what are some of the things that them dots can do? Well,
the most important thing is that quantum dots can have
sort of designer optical properties. Remember that the reason that
(30:06):
some things look a certain color is because they reflect
light of that color, which means they're absorbing all the
other colors. So if you can design a material that
absorbs light at certain frequencies and other frequencies, you can
basically design its color to be whatever you like. And
if you want to design a very crisp display or
you want to marker, you can inject into your experimental
(30:27):
subject and watch as something flows around. Then you want
to be able to design its optical properties. And so
as you change the size of your quantum dot, for example,
you change the energy that that electron can absorb, which
changes how it looks optically. It's kind of sounds like
you're just making colors, though, Like isn't that how color works? Usually,
(30:49):
like the atom in like a blue paint reflect blue
light especially. Yeah, that's exactly what we're trying to do.
We're just making colors, but we're making very crisp, well
the fine colors, right. You want something which absorbs very
very narrowly or only reflects a very very narrow range
of frequencies. So it's like exactly blue or super duper
(31:10):
perfect red or exactly the green you were looking for.
I see quantum paint is the new marketing term. Yeah, exactly.
And so this makes it if you're going to build
a television, for example, it makes it much easier to
get crisp colors. You know exactly how to combine your
various little layers to get exactly the color you want
(31:32):
on screen. So it's simpler, it's cheaper, it's more efficient.
You don't need, like, you know, complicated filters to get
rid of the edge effects that you didn't really want
because you were forced to use the atoms that physics
gave you. You You can invent your own atoms to devise
your own quantum screen. But can you make these quantum
dots change the light or turn them on and off?
How would this work? How would this television work? Would
(31:53):
it be just a one image television? I think each
one is essentially like a filter. So you put some
source of light behind a layer of red quantum dots,
and which you get our red light. Or if you
put light behind the layer of green condom dots, you
get green light or blue light. So it operates on
the same basic principle as all your other televisions, which
(32:16):
have for example blue LEDs or green l e d
s or red l e d s. But this is
the way that you get the pure light instead of
all the white light. Be like super precise colors. That's
the idea. Super precise colors. Yeah, extra precise, extra precise.
And also because they're more efficient they show exactly the
color you want, there's lower energy consumption and so you
(32:38):
can have like longer lifetimes. And that's the turkey part,
I guess is how you make them at the size
of a television because you have to make a lot
of them. You've got to make a lot of them
yet exactly, and they have to survive my kids dropping
my phone for example. They do. But you know, because
they can be sort of printed on anything in their
microscopic they can potentially be you for things like you know,
(33:01):
rollable or flexible displays in the future, all right, or
like a like a blanket TV, yeah, or TV you
could like fold up and you know, stick in your
pocket or something. Alright. What else can we use quantum
dots for? Another awesome application is in solar cells, because
again you can really tune the absorption and the emission
(33:23):
then you can get quantum dots that absorb light at
exactly the peak wavelength that you're seeing on your roof,
you know, so you can make sure that like the
peak efficiency for absorption is where most of the light
actually is, right because right now it's kind of fuzzy, right, Yeah, exactly,
it's kind of fuzzy. And these solar cells are expensive
to produce. But if you could get quantum dots ramped
(33:44):
up so you can make a lot of them, you
can make basically like solar power paint, and you could
like have a solution with quantum dots in it that
you basically paint onto a surface and it becomes a
solar power cell. What Like, you can just paint your
roof and then attach some wires to it and it's
a solar panel. Yes exactly, that is wild. Yeah, they
would absorb the energy and they would like chain themselves
(34:06):
up so they can pass a current along and so
that would be pretty awesome. Like, you know how cool
it is that you can paint like a chalkboard on
a wall and it actually kind of works. That's pretty cool. Well,
this is like a step beyond that. It's like painting
an electrical device onto your roof or anything, really your
car or your hat or really you're you can get
a tattoo. Can you get a solar cell tattoo, you know,
(34:29):
inked on your skin? It would be awesome, and you
can charge your phone just by against your body. Yeah,
and the tattoo should look like a solar cell, and right,
that would be super cool. It looks like a solar
cell and acts like a solar cell. Well, technically you
could make it look like anything. Yeah, you could. You
can make it look like a rose or your grandma,
(34:49):
and it would be helping you save some energy, would
be cool? It power your phone? Yeah cool? All right,
so you can make solar paint. What else can you
do with it? You can also use it in science.
A lot of biology uses something called bio labeling, where
you like inject some substance into a bacterium or into
a larger animal, and you want to follow, like where
did it go? Where is it being used? Where is
(35:10):
the active site where it's like being actually processed. So
these quantum dots are like more stable and brighter than
most of the other dies, and so they're much more useful.
They can like last for months, but they're also toxicing,
aren't they. Yes, they're poisonous. I guess if you don't
want your sample to live very long. Yeah, a lot
of them. Because you want to engineer particular optical properties
(35:32):
require you to use various substances like cadmium, which is
pretty toxic. So we're not at a point where you
want to You know, your kids eating a spoonful of
quantum dots are definitely not. But you know, if you
don't mind killing your bacteria to learn about how it's
doing something or how it's defending itself, then it's all right.
Does that put a kaboche on the tattoos as well?
(35:53):
If you tattoos cadmium into your body, that would give
you other kinds of cancer. Yes, not recommended. Yet, people
are working on ways to make quantum dots that don't
require a cadmium or other toxic materials, so I'm pretty
sure that in the future will have humans safe quantum dots. Alright, cool,
What else can we make with quantum dots? Well, we
(36:13):
can also build super tiny electronics. You know about this
material called graphine, which is basically like a lattice of
carbon built in a super fancy interesting way that has
fancy molecular properties. Well, graphing is really stable and really
conductive even when it's cut into super tiny devices like
one nanometer wide. And so you can build like the
(36:35):
tiniest of electronics using graphing single crystals, which are technically
also quantum dots that you can make a circuit that's
literally like one atom talks to another atom, and then
that atom talks to another atom. Yeah, exactly, And so
this is like one potential way to even further miniaturize
our electronics. But wouldn't it get quantum at that point
(36:57):
or like, would it still behave like a regular circuit.
It would get want them exactly, but so you have
to define it to do exactly what you want. But
you can build transistors out of single atoms, and single
electron transistors are a thing you can do. The chemistry
and the physics is a little bit different from the
way we're currently doing electronics, but you can build the
basic components we need for circuits out of these graphing
(37:18):
single crystals. All right, Well, but it sounds like maybe
the technology that's pushing it at least into the mainstream
is this idea of a quantum TV. So how far
away are we from that? Are they actually starting to
make them or think about them or Netflix investing on this. Yeah,
quantum TVs are negative five years away, which means they've
(37:39):
been on the market since about What what do you mean,
like you can put in money to buy a quantum
TV ten years in the future. No, that means five
years ago, if you went on Amazon and typed in
quantum l e ED there were TVs for sale that
you could purchase. You could go purchase a quantum l
a ED TV right now. But it's not really made
out of quantum dots, is it. No, it really has
(38:00):
quantum dot technology. Oh, this is really a thing. Really wow, Okay,
it's not a future technology. It's like five years ago technology.
It's like Obama years technology. Exactly. Obama probably has a
quantum TV and he's probably sitting in front of it
eating quantum cookies right now, because yes, we can watch
(38:21):
a quantum TV. Really, So if I buy a quantum TV,
it has like quantum dots in it, Yeah, exactly, it
has a quantum dot layer which filters this like led
backlight and helps reduce better color. So, like we were
saying at the top of the program. Quantum TVs are
not a scam. They are real and they actually use
quantum technology. Unlike quantum yogurt and quantum hamsters and quantum
(38:43):
massage and quantum stealth technology. This is real applications of
quantum mechanics on your wall right right. Although you know,
technically yogurt does have quantum particles in it. Everything tastes
like particles. In the end, it's just a good figure
and gut. All right. So have you seen a quantum TV?
Does it look crisper and does it look nicer? I
(39:04):
think you should do some research and you'll maybe buy
yourself a TV with your grant money. Yeah, maybe I will.
You know, I did look up quantum TVs, but I
can only watch a video of a quantum TV on
my non quantum screen, and so it doesn't really come through.
It's like looking at a video of a high definition
television on your low definition television. It's not very impressive.
(39:24):
So I've never actually seen one. And also the only
clip you can watch is a clip of vaculating quantum leap,
which doesn't help you. Yeah, they need to work on
the quantum content, really, but no, I've never actually seen
one in the wild. So any listeners out there that
have a quantum screen right to us and let us
know how awesome is it. Yeah, take a picture and
send it to us to see how good it looks.
(39:46):
Take a quantum picture. Yeah, we'll get it and not
get it at the same time. All right, Well, um,
that's pretty cool that this technology is out there. It
is being used on televisions. People are technically potentially watching
Netflix right now with the quantum TV, I hope. So
all right, and it might potentially give some pretty amazing
technologies in the future. That's right. With the power to
(40:09):
understand the quantum world comes the ability to engineer it
and have it do all sorts of things that normal
atoms cannot do. So it's not just that physics is
playing with the universe because we want to understand, but
sometimes there are actual benefits for humanity. Yeah, yeah, stay
tuned for those quantum tattoos. Will every physicist get one?
Just do like, you know, show solidarity and team spirit.
(40:33):
I don't think you could ever say every physicist will
do anything apply for grants. All right, Well, we hope
you enjoyed that, and we hope you look at the
world a little bit different. Sometimes, quantum technology and quantum
effects are there for us to see and for us
to bench watch with. Well, thanks for joining us, See
you next time. Thanks for listening, and remember that Daniel
(41:02):
and Jorge Explain the Universe is a production of I
Heart Radio. For more podcast for my Heart Radio, visit
the I Heart Radio Apple Apple Podcasts, or wherever you
listen to your favorite shows. Ye
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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