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Have you ever asked yourself
about the actual nature of the universe?

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I'm not talking about
any abstract universe but our universe,

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the one in which we all live,
the one where you are now.

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Have you ever thought about
what you body was really made of?

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Or the air you breathe
or even the very chair you are sitting on?

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If the answer is yes,

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then you might have noticed
that around you

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you can find clues
that can help you decode all that.

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For example, if I grab my glass,
you see there is water in it,

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and I throw it at you, here,

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some of you would move aside a little.

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Nobody in this room,
or anywhere else on Earth

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ever thought that once
you throw the water,

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it would stop halfway in the air
turn around and go back into my glass.

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And why is that?

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We all have this feeling
that some laws of Nature actually exist,

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and that those very laws cannot be broken.

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The aim of theoretical physics
is to figure out what those laws are.

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One have to admit that, as humans,
we are rather good at that.

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Just to give you an idea: since Newton,

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we can all describe every single thing
that is happening around us,

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including the state of objects.

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That, we know how to do.

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But since Newton,
we went a little further than that.

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We even entered a world
that goes beyond our senses.

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A world in which our intuition
no longer applies.

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It is a wonderful world,
and I'll tell you why.

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In 1905, Albert Einstein taught us

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that light is made of
tiny pieces of energy.

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In Latin, "tiny pieces"
would be translated as "quanta."

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What Einstein and other fellows did,
was to open us up on a new world,

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the world of quantum mechanics
and quantum physics,

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a tiny world that is the world of
luminous rays.

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I'll ask you to imagine that, for a
moment, you are in 1942 in Paris,

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where a young scientist
just got his thesis published

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He is 32, and his name
is Louis de Broglie,

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and he states something extraordinary.

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In support of his calculations,
he states the light that is around us,

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and this matter
that your bodies are made of

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are not that different from one another.

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The matter would actually
be made of those tiny pieces of energy.

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That would mean that matter itself
would follow the laws of quantum science.

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And for this,

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De Broglie achieved the dream
of every PhD student on earth

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when receiving a Nobel Prize
for his thesis, 7 years later.

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And that's not so bad after all.

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On the founding fathers of quantum physics

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immediately got his hands on this idea

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and started to work on trying to find out

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how the whole world
of the infinitely small works.

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And guess what?

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He succeeded in finding an equation

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that he named the Schrödinger's equation.

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It describes the way particles behave
within our universe.

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In a few words, he did
for the world of the infinitely small

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what Newton did for the world around.

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If you shoot an arrow,
Newton would tell you where it will land.

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If you throw a particle,

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well, Schrödinger would tell you
what it will become.

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Unfortunately, in the world
of the infinitely small,

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particles are no arrows.

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They are not even like small balls.

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Instead, you have to imagine a kind
of cloud filled with small balls

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that are either present or missing,
that exist or don't exist

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and that are overlaid
and that are almost everywhere.

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Schrödinger's equation describes
how this cloud will evolve through time.

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what he eventually found was very strange.

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Just to give you an idea

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of what it could mean
from our world's perspective,

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he came up with a thought experiment

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he named the Schrödinger's cat experiment.

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Here it goes: in this box, there is a cat.

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(Mioawing)

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It might have been sleeping.
Anyhow, there is a cat.

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But there is more than a cat.

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It didn't sound very happy,
because on its side

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Schrödinger placed, and so did I,
a radioactive substance.

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What is a radioactive substance?
It is a substance we can split into two.

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That's why the first row had to sign
the legal discharge earlier,

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it's radioactive in there.

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So, we have a substance
that can be split into two

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without us knowing in advance
whether or not it will happen.

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So, there is this little substance inside

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and with the one I place here,
there is a 50/50 chance it will break,

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or be blown apart between now
and the end of the experiment.

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But Schrödinger did not only did that.

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With this little substance,
he added a device, as smart as sadistic,

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that would release a poison
and eventually kill the cat

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in case the substance blows away.

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If on the contrary the substance
stays as is, the cat is safe.

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The laws of quantum physics tell us
as long as no-one has looked inside,

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as long as no-one opened the box,

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the radioactive substance has blown away
but at the same time, hasn't.

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It means the poison has
and hasn't been released.

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Consequently, the cat inside
is not dead or alive, but dead and alive.

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It sounds completely insane, I agree.

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But after all, that's what maths
tells us, and they are positive.

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If the laws of quantum physics
as we know them are correct

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then Schrödinger and his equation
will tell you that in this box,

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the cat is both dead an alive.

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Let's have look.

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(Miaowing)

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Well, at least it's not dead,
which is good.

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But you see, there was only one cat

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as you might have expected
and you might be a bit relieved

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that the cat is alive and not dead.

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As for me, it disturbs a lot
that there is only one cat inside.

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I believe in maths
and all the physics that's behind it,

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and if maths says
that there should be two cats inside

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the questions is:
where is the dead cat now?

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It should then be there but is not.
So where is it?

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As crazy as it sounds,

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scientists are actually paid
to try and answer this very question.

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(Laughter)

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They were even paid for years.

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Schrödinger published
this thought experiment in 1935.

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For a decade after that, maybe even two,

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almost all the scientist on earth
have been looking for the dead cat.

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Up until a young American
named Hugh Everett III

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came up with an incredible solution.

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He thought to himself that if Einstein
and De Broglie were really right,

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which seemed to be the case,

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then light and matter are quantum

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since our whole universe
is made of light and matter,

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then, there is no reason at all
that the universe itself

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would not be quantum.

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And consequently, a superposition
within its different states,

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where there are many possibles.

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What he means is
that when I opened the box,

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two cats were inside

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and when I opened it,
our whole universe split into two:

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one where we live now
and where the cat is alive,

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and the other where it was dead.

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This very universe
would be universe parallel to ours

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that would remain forever.

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At the end of one his lessons
on quantum physics,

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Einstein told his students,

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"If you understood what I said,
it means I wasn't clear enough."

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(Laughter)

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Hugh Everett III
didn't get the Nobel Prize

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because he published
this paper with his thesis

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on the contrary, he abandoned physics,
thinking it was rubbish.

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(Laughter)

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He might have been right though.

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But at the time, to check his theory

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would mean we would need to see
every single atom.

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See them in their overlapping state,

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to try them out
and actually observe them.

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Then again, at this time,
it was experimentally out of the question.

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But not now anymore.

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At the end of 1990s,

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in the Teacher Training College's
laboratories in Paris

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Pr. Serge Haroche's team
succeeded in creating

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an experiment categorized
as "Schrödinger's cat-like."

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It wasn't with a cat,
but with big atoms and light.

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And from this experiment,
he could see that atoms

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were in overlapping states.

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The same kind as a cat
both dead and alive.

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He even saw those two states vanish
to leave space for only one,

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and, in a certain way, to give birth
to the world we got used to living in.

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This very experiment got him
the Nobel Prize in Physics 3 years ago.

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We started in 1924
with Louis de Broglie's Nobel Prize

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and arrived in 2012 with Serge Haroche's,

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following an idea where we traveled
different times and lands.

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Why did I tell you all this?

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Why did we follow the hare-brain ideas
of all those loony scientists

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talking about cats dead-alive cats
and parallel universe all over the place?

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Is it of any use?

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I could honestly understand
that you wouldn't get

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why we actually fund research.

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But, it turns out you'd be wrong.

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From Broglie's discoveries
to Schrödinger's equation

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many everyday life objects
have seen the light of day:

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computers, mobile phones, lasers

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and almost all medical equipment
you can find in a hospital.

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But some of you will ask,
"What about Haroche's discovery?"

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Well, it turns out that it allows for

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a new industrial
and technology revolution.

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By succeeding in considering
the cat as both dead and alive

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he opened the way
to computers of the future

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that they call quantum computers.

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A quantum computer is a machine

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that uses the overlay
of atoms state within its heart.

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Does that makes sense?

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Thanks to this system,
those small atoms and those machines

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are capable of calculating
as if they were

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in billions of different
parallel universes at the same time.

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This means a single one of these computers
would make all of the computers

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we have nowadays, look like abaci.

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That's just that simple.

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Fundamental research
is a rather understated discipline,

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that can sometimes be completely secret.

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Yet, it is the origin of many revolutions

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and the genies behind them

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can emerge anytime and anywhere.

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Here is an example, Serge Haroche,
the same man we talked about earlier,

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who was born in Casablanca, Morocco
and arrived in France when he was 12.

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As a small digression,
I'd like to pinpoint the fact

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if we had closed our borders back then,
France would have lost a Nobel Prize

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and its hypothetical
and amazing applications.

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(Applause)

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Scientific knowledge
belong to every single person,

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you, me, newborns here,
or somewhere else on Earth.

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It is our duty to share and pass it on.

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It is for everyone's sake
that I tell you this.

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Besides, it is very likely
that, in the future,

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a child from another country
will hold the keys of our future here

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and not of a parallel universe.

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Thank you very much.

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(Applause)