Transcriber: Shahed Abdalazez Reviewer: Robert Tucker
You live in a quantum world.
You take advantage of it every single day, and you don't even know what it means
In the morning you wake up,
you have a shower, you fry your eggs, toast your bread, pour your coffee.
You brush your teeth, pack your laptop, take your phone,
close the door and run for the tram.
That is one hour of your daily life,
sponsored by at least one million of scientific discoveries.
I'm here as a quantum researcher
to tell you why quantum mechanics is amazing,
and how quantum computers are going to change your lives.
As scientists, we really try to explain the world,
we want to explain the phenomena and the effects that we see around.
We see that something is moving around, and we want to predict its trajectory,
or we feel that something is heating up, or even bursting,
and we want to understand why this is happening.
So, all these things were already observed and unexplained,
a long time ago.
When I say a long time ago, I'm talking like a few centuries.
Those are the classics.
So, things like gravity, thermodynamics, maybe electromagnetism,
they were explained long time ago.
But human curiosity wanted to go a little bit farther.
So, humans are starting to look into the really small, tiny things.
At some point, they found things like atoms, photons, or electrons,
and they could no longer explain
what was happening with these little particles,
using the set of laws
that they were using for the bigger things.
So, they realized they needed a new set of laws.
So, in the 1920s, very important and renowned scientists,
like Schrödinger, Heisenberg, Bohr,
came up with the first mathematical framework
for quantum physics.
And that was really revolutionary,
because from that moment on,
we would distinguish the world into two different worlds.
So, we would have this set of laws
that would explain the classical mechanics,
and we would have also the set of laws that would explain the little things,
the quantum particles.
So, actually, this was really a big thing,
and it changed the whole thing,
but I want to bring another differentiation here today.
And this distinction is about what was told to us,
and what is untold to us.
So, let me try to explain this a little bit.
When we are children,
when we are at school,
we believe everything our teachers tell us.
I'm not saying we shouldn't have, I'm not saying they were lying to us.
I'm just saying whatever they told us, we'd be left, "Bah! Cool."
And so they'd tell us about gravity.
And if you really think about it,
gravity, it's amazing,
it's even unbelievable.
There is like an imaginary, transparent, invisible force
that is pulling you down 24/7,
and nobody questions it,
everybody is like, "Oh yeah, gravity, I've heard of it, yeah."
(Laughter)
But what about those things that we weren't told about?
This is quantum physics.
Because of that, because we never heard about it,
because our teachers didn't tell us about it,
we feel really disconnected to this world.
We feel so disconnected,
the only thing we know about it is that it's difficult to understand,
counterintuitive.
So, we just don't even give it a try.
But let me tell you something:
If I can pretend to understand quantum physics,
so can you.
(Laughter)
So, now this when we do research,
we don't actually take a notebook,
sit on a stone,
and just look at the world pass by.
We have a different approach.
We try to implement everything in our laboratories,
or what is actually an even lazier approach,
we try to implement everything in our little computers.
And this is kind of where we are stuck at the moment
because the calculations we want to do
are not possible to be made in our classical computers,
even in the classical supercomputers.
So, now, what is the concept of a computer?
Let us start very basic.
In any computer, what we need to do is to encode information in a system.
In our computers, we call the system a bit.
And to be a little bit scientific, a bit is a binary system.
But it's just a technical word to say
that it's a system that can be in two different states.
Usually, we refer to it as 0 or 1.
In reality, this is just a little transistor
where we just apply a voltage, or apply no voltage at all,
and this is pretty much our 1 or 0.
But now what happens
when quantum mechanics wants to be, like, simulated
in a normal computer?
Well, quantum mechanics is beautiful, it's really gorgeous, believe me,
but it's also a little bit complicated.
And this is where our computers get us stuck.
There are many characteristics that make it really beautiful,
and really complicated,
but there are two that I think are most important.
One of them is quantum superposition,
which means that a quantum particle is not in a defined state,
but it can be in a superposition of two different states.
And on the other hand, there is the quantum uncertainty,
which means that we don't know the state of the particle
until we measure it.
So, OK, let's try to bring a little light, hand-waving example,
and see if we all understand it.
Imagine I'm going to toss a coin.
It is still up there in the air until we get to the example.
So, basically, we have the coin flipping around,
and while it is in the air,
the state can be somewhere between heads and tails.
So, we can say
it is in a superposition of heads and tails.
And at the same time,
while it is in the air, we don't know what the state is.
However, when we catch the coin,
we are sort of making a measurement,
making an observation,
and we are disrupting the system.
And, at the same time,
we are also defining the state of the coin,
because it is no longer in a superposition,
but it's going to be in 0 or 1,
which is the same as heads and tails, right?
So now, I've said in normal computers, we just have a bit that can be in 0 or 1.
But if we would have a quantum computer,
we would have something that we call "quantum bit",
or what is the same, a qubit.
In this case, it's not only in 0 or 1,
but it is in 0 and 1, at the same time.
So, now let's imagine we have 20 particles.
20 is a very small number,
everybody can imagine 20 particles,
in a box if you want.
And now this seems kind of easy.
But what happens if every single particle
can be in a superposition of two different states?
Now you say,
"OK, it's 22 different states, it cannot be that bad."
But actually, if you want to consider the entire system,
and if you want to consider every single possible combination,
you would end up with more than a million combinations.
And this is exactly where quantum computers are really beneficial
and can boost the computing power.
Because our qubits can naturally be in a superposition of states,
which means that they can naturally consider
all the possible combinations at once.
So, now, let's say I've convinced you, and fine, quantum computers are amazing,
but how do we actually build them?
So, there are many different ways of building quantum computers.
And basically, the main difference is
the system in which we encode the information
So, we can use photons, we can use atoms,
we can use superconducting circuits.
The only thing that matters
is that all these systems can be in a superposition
of two different states, 0 and 1.
In my case, I worked with photons.
I love their properties, they're gorgeous,
but they are also a pain to work with.
As many photons as we get from the sun,
or as many photos as we can create in a laser system,
these little bastards love bunching with each other,
all the time.
So, actually getting single photons, one at a time,
is one of the major challenges
that we have in photonic quantum computing.
Believe it or not, I spent my entire PhD
trying to get single photons using graphene.
And we made quite some good steps forward,
but it's still a long way to go.
So, there are other systems, as I said.
Another one would be atoms.
They have their own advantages, but also their own disadvantages.
In the case of atoms,
they get really destructive with everything around them.
They like interacting with everything, all the fields around them.
And because of that, it's very difficult to get them isolated.
In the case of superconducting circuits, they also have their own advantages.
But they also like being really cold.
And when I say really cool, I'm talking colder than outer space.
So, this is certainly a big challenge in a laboratory.
So, what I'm trying to say is:
All the systems have their advantages and disadvantages.
So, basically, it's not clear
who is going to win this race of quantum computing.
But, of course, like in any other competition,
we need to define our criteria.
How are you going to define who the winner is?
So, in quantum computing,
we talk about something that is called "quantum supremacy".
And I thought, "How am I going to explain quantum supremacy?"
And I thought, I'll just show them what Wikipedia says,
because that's what we all do, don't we?
So, this is what Wikipedia says:
"In quantum computing,
quantum supremacy is the goal of demonstrating
that a programmable quantum device can solve a problem
that no classical computer can solve in any feasible amount of time."
And the funny part comes in a little parenthesis -
it's right after -
and it reads,
"irrespective of the usefulness of the problem".
(Laughter)
So, actually, this may not make any sense to you,
but it thoroughly does.
Because, nowadays, every single quantum computer that is built,
is built with a specific purpose,
with the specific purpose of solving one, and only one, problem.
So, basically, companies and research institutions,
they're just looking for the problems that their quantum computers are good at.
Then they compare the performance of the quantum computers
with the classical computers.
So, whenever quantum computers are ridiculously faster than classical ones,
we are talking about quantum supremacy.
In 2019, Google presented the first quantum computer.
It was based on superconducting circuits, and they got up to 53 qubits.
And they claimed to solve one problem within 200 seconds,
whereas the classical counterpart would have taken 10,000 years.
So, a year later, IBM actually claimed
that this could have been solved within 2.5 days.
(Laughter)
But this is not the point of my talk,
and none of the companies is paying me to advertise their products,
so I'm just going to leave it there.
The second and latest quantum computer
was presented by the University of Science and Technology of China.
This was this year.
And this was based on photons.
They got up to 76 qubits.
They show that they could compute a problem within 200 seconds,
whereas the classical computer would have taken 2.5 billion years.
So, now, if we really look at what they were solving,
without offending anyone here,
it was kind of useless.
But don't get me wrong, this is what fundamental research is about.
We make a little step forward,
and it doesn't look like we're getting anywhere,
but this step forward is so important to eventually get to the ultimate point.
This is what research is about.
So, we shouldn't focus on what's the applicability of this exact step,
but like, where is this taking us to?
Because I'm pretty sure the first car was slower than bikes.
And here we are, nowadays with our fancy cars
that can go way faster than what they're allowed to.
So, when I'm talking about the impact of low quantum computers,
what is this about, what am I talking about?
Am I talking about, I don't know,
maybe Netflix not getting stuck when we're in the middle of the movie,
or Tinder getting a little bit more efficient, looking for matches,
or maybe finally understanding the logic behind the price of the flight?
Unfortunately, this is not
what quantum computers are going to help us with,
But there's something very, very important they are going to help us with,
and this is combinatorics.
Before I said that because quantum particles are qubits
[and] can be naturally in a superposition of states,
they're very good at looking into different combinations at once.
So, now imagine that you have a pile of pieces,
and they tell you, you can put them together in any way you want.
And this is exactly what chemical and biological engineering is about.
They have a bunch of atoms,
the entire periodic table, actually.
and they can put them in any way they want
to get the drugs
with the properties that they are looking for.
So, now if you imagine, like, the billions and trillions of ways
in which you can put atoms together,
this is exactly where our classical computers are crashing.
And this is exactly where
quantum computers are going to really boost
the computational power.
Another very important point when we really consider different options
is when we have to make decisions
that consider many parameters at the same time.
So, you can have many combinations at the same time,
And this is exactly what artificial intelligence is about.
As humans, we are very good at considering the consequences of our acts ...
sometimes.
But basically, when we want to make our robot, our machines, smarter somehow,
we just want them to be able to look at different parameters, different options,
and give us the best one,
because they have gone through all of them.
So, hopefully, I have convinced you that quantum computing is amazing,
and that we should thoroughly go for it.
The question is when is this going to happen?
So, unfortunately, I have no idea.
(Laughter)
And it's not because I didn't pay attention at the university,
it's because nobody knows.
It could be a decade, two decades, half a century.
To be honest, your guess is as good as mine.
But there is something I know.
And this is that it's going to happen
because in theory, we know how to build a quantum computer.
The problem is that our technology is classical.
It's very big, it's very rough,
and basically, we have to adapt all our machinery,
all our technology,
to be able to deal with these little quantum particles.
So, basically, one could say that it is just an engineering problem.
Just.
(Laughter)
Thank you.
(Applause)