Have you ever asked yourself about the actual nature of the universe?
I'm not talking about any abstract universe but our universe,
the one in which we all live, the one where you are now.
Have you ever thought about what you body was really made of?
Or the air you breathe or even the very chair you are sitting on?
If the answer is yes,
then you might have noticed that around you
you can find clues that can help you decode all that.
For example, if I grab my glass, you see there is water in it,
and I throw it at you, here,
some of you would move aside a little.
Nobody in this room, or anywhere else on Earth
ever thought that once you throw the water,
it would stop halfway in the air turn around and go back into my glass.
And why is that?
We all have this feeling that some laws of Nature actually exist,
and that those very laws cannot be broken.
The aim of theoretical physics is to figure out what those laws are.
One have to admit that, as humans, we are rather good at that.
Just to give you an idea: since Newton,
we can all describe every single thing that is happening around us,
including the state of objects.
That, we know how to do.
But since Newton, we went a little further than that.
We even entered a world that goes beyond our senses.
A world in which our intuition no longer applies.
It is a wonderful world, and I'll tell you why.
In 1905, Albert Einstein taught us
that light is made of tiny pieces of energy.
In Latin, "tiny pieces" would be translated as "quanta."
What Einstein and other fellows did, was to open us up on a new world,
the world of quantum mechanics and quantum physics,
a tiny world that is the world of luminous rays.
I'll ask you to imagine that, for a moment, you are in 1942 in Paris,
where a young scientist just got his thesis published
He is 32, and his name is Louis de Broglie,
and he states something extraordinary.
In support of his calculations, he states the light that is around us,
and this matter that your bodies are made of
are not that different from one another.
The matter would actually be made of those tiny pieces of energy.
That would mean that matter itself would follow the laws of quantum science.
And for this,
De Broglie achieved the dream of every PhD student on earth
when receiving a Nobel Prize for his thesis, 7 years later.
And that's not so bad after all.
On the founding fathers of quantum physics
immediately got his hands on this idea
and started to work on trying to find out
how the whole world of the infinitely small works.
And guess what?
He succeeded in finding an equation
that he named the Schrödinger's equation.
It describes the way particles behave within our universe.
In a few words, he did for the world of the infinitely small
what Newton did for the world around.
If you shoot an arrow, Newton would tell you where it will land.
If you throw a particle,
well, Schrödinger would tell you what it will become.
Unfortunately, in the world of the infinitely small,
particles are no arrows.
They are not even like small balls.
Instead, you have to imagine a kind of cloud filled with small balls
that are either present or missing, that exist or don't exist
and that are overlaid and that are almost everywhere.
Schrödinger's equation describes how this cloud will evolve through time.
what he eventually found was very strange.
Just to give you an idea
of what it could mean from our world's perspective,
he came up with a thought experiment
he named the Schrödinger's cat experiment.
Here it goes: in this box, there is a cat.
(Mioawing)
It might have been sleeping. Anyhow, there is a cat.
But there is more than a cat.
It didn't sound very happy, because on its side
Schrödinger placed, and so did I, a radioactive substance.
What is a radioactive substance? It is a substance we can split into two.
That's why the first row had to sign the legal discharge earlier,
it's radioactive in there.
So, we have a substance that can be split into two
without us knowing in advance whether or not it will happen.
So, there is this little substance inside
and with the one I place here, there is a 50/50 chance it will break,
or be blown apart between now and the end of the experiment.
But Schrödinger did not only did that.
With this little substance, he added a device, as smart as sadistic,
that would release a poison and eventually kill the cat
in case the substance blows away.
If on the contrary the substance stays as is, the cat is safe.
The laws of quantum physics tell us as long as no-one has looked inside,
as long as no-one opened the box,
the radioactive substance has blown away but at the same time, hasn't.
It means the poison has and hasn't been released.
Consequently, the cat inside is not dead or alive, but dead and alive.
It sounds completely insane, I agree.
But after all, that's what maths tells us, and they are positive.
If the laws of quantum physics as we know them are correct
then Schrödinger and his equation will tell you that in this box,
the cat is both dead an alive.
Let's have look.
(Miaowing)
Well, at least it's not dead, which is good.
But you see, there was only one cat
as you might have expected and you might be a bit relieved
that the cat is alive and not dead.
As for me, it disturbs a lot that there is only one cat inside.
I believe in maths and all the physics that's behind it,
and if maths says that there should be two cats inside
the questions is: where is the dead cat now?
It should then be there but is not. So where is it?
As crazy as it sounds,
scientists are actually paid to try and answer this very question.
(Laughter)
They were even paid for years.
Schrödinger published this thought experiment in 1935.
For a decade after that, maybe even two,
almost all the scientist on earth have been looking for the dead cat.
Up until a young American named Hugh Everett III
came up with an incredible solution.
He thought to himself that if Einstein and De Broglie were really right,
which seemed to be the case,
then light and matter are quantum
since our whole universe is made of light and matter,
then, there is no reason at all that the universe itself
would not be quantum.
And consequently, a superposition within its different states,
where there are many possibles.
What he means is that when I opened the box,
two cats were inside
and when I opened it, our whole universe split into two:
one where we live now and where the cat is alive,
and the other where it was dead.
This very universe would be universe parallel to ours
that would remain forever.
At the end of one his lessons on quantum physics,
Einstein told his students,
"If you understood what I said, it means I wasn't clear enough."
(Laughter)
Hugh Everett III didn't get the Nobel Prize
because he published this paper with his thesis
on the contrary, he abandoned physics, thinking it was rubbish.
(Laughter)
He might have been right though.
But at the time, to check his theory
would mean we would need to see every single atom.
See them in their overlapping state,
to try them out and actually observe them.
Then again, at this time, it was experimentally out of the question.
But not now anymore.
At the end of 1990s,
in the Teacher Training College's laboratories in Paris
Pr. Serge Haroche's team succeeded in creating
an experiment categorized as "Schrödinger's cat-like."
It wasn't with a cat, but with big atoms and light.
And from this experiment, he could see that atoms
were in overlapping states.
The same kind as a cat both dead and alive.
He even saw those two states vanish to leave space for only one,
and, in a certain way, to give birth to the world we got used to living in.
This very experiment got him the Nobel Prize in Physics 3 years ago.
We started in 1924 with Louis de Broglie's Nobel Prize
and arrived in 2012 with Serge Haroche's,
following an idea where we traveled different times and lands.
Why did I tell you all this?
Why did we follow the hare-brain ideas of all those loony scientists
talking about cats dead-alive cats and parallel universe all over the place?
Is it of any use?
I could honestly understand that you wouldn't get
why we actually fund research.
But, it turns out you'd be wrong.
From Broglie's discoveries to Schrödinger's equation
many everyday life objects have seen the light of day:
computers, mobile phones, lasers
and almost all medical equipment you can find in a hospital.
But some of you will ask, "What about Haroche's discovery?"
Well, it turns out that it allows for
a new industrial and technology revolution.
By succeeding in considering the cat as both dead and alive
he opened the way to computers of the future
that they call quantum computers.
A quantum computer is a machine
that uses the overlay of atoms state within its heart.
Does that makes sense?
Thanks to this system, those small atoms and those machines
are capable of calculating as if they were
in billions of different parallel universes at the same time.
This means a single one of these computers would make all of the computers
we have nowadays, look like abaci.
That's just that simple.
Fundamental research is a rather understated discipline,
that can sometimes be completely secret.
Yet, it is the origin of many revolutions
and the genies behind them
can emerge anytime and anywhere.
Here is an example, Serge Haroche, the same man we talked about earlier,
who was born in Casablanca, Morocco and arrived in France when he was 12.
As a small digression, I'd like to pinpoint the fact
if we had closed our borders back then, France would have lost a Nobel Prize
and its hypothetical and amazing applications.
(Applause)
Scientific knowledge belong to every single person,
you, me, newborns here, or somewhere else on Earth.
It is our duty to share and pass it on.
It is for everyone's sake that I tell you this.
Besides, it is very likely that, in the future,
a child from another country will hold the keys of our future here
and not of a parallel universe.
Thank you very much.
(Applause)