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High above the Atlantic Ocean,
on one of the Canary Islands,

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a team of pioneering scientists
is setting up an experiment

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that will span the vast scales
of the cosmos...

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..and could confirm our perception
of the universe is an illusion.

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I'm checking the signals
from the cosmic

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random number generator
and it looks pretty good.

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They're connecting two of Europe's
largest telescopes and attempting

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to use galaxies billions of light
years away to control intricate

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measurements of tiny particles
of light here on Earth.

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They're testing the existence
of perhaps the strangest idea

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in science - quantum entanglement.

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Entanglement is this very powerful
but strange connection that exists

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between pairs of particles.

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The effect is almost magical.

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As if something here can
mysteriously affect something there.

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Can particles be connected
as if they're joined together,

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even if they're millions
of miles apart?

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Entanglement opens up new venues
for communication, for computation

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and for understanding the nature
of space and time and the beginning

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of the universe.

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Einstein rejected the idea, calling
it "spooky action at a distance".

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It's so beautiful, but what the heck
is behind it?

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So is entanglement real?

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Do we live in Einstein's universe
of common sense laws, or a bizarre

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quantum reality that allows strange
connections across space and time?

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Will the team
prove Einstein right...

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Moving.

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..or wrong?

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Yeah, that's good.

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We do have a test.
We are acquiring data right now.

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As with so many of the most
important ideas in physics,

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the story of quantum entanglement
begins with Albert Einstein.

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In 1927, he travelled to Brussels
to attend a meeting

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about a new theory that described
the micro world of atoms

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and tiny particles -
quantum mechanics.

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Quantum mechanics is one of
the most amazing intellectual

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achievements in human history.

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For the first time, scientists
were able to probe a world

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that was, until then,
quite invisible to us.

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Looking at the world at the scale
of atoms a million times smaller

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than the width of a human hair.

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One way to think about the scales
is that if you take an everyday

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object like a soccer ball,

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and you enlarge that soccer ball

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so that actually you can see
the individual atoms, you roughly

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have to make it the size
of the Earth.

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And then move into that planet.

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Then you are in the world
of atoms and particles.

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It was the nature of
fundamental particles

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that make up the world
we see around us

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that Einstein had come to Brussels
to discuss, and it was here

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that Einstein entered into
a heated debate that would lead

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to the discovery of
quantum entanglement.

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A concept that will trouble him
for the rest of his life.

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With two PhDs from Harvard,
and now a leading professor at MIT,

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David Kaiser has studied
this dispute and has come

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to the place where it all began.

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This is the original
Solvay Institute building,

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beautiful, grand building.

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And this is the place,

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back in October 1927,

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where the fifth
Solvay Conference was held.

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This amazing week-long series
of discussions

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on really what the world is
made of, and the nature of matter,

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and the new quantum theory.

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And these steps are the very steps
on which this famous group

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photograph was taken.

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It is a collection of some
of the most brilliant people

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in the world. Here in the front row

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we see Albert Einstein and the great
Marie Curie and Max Planck.

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In the back row, standing,
the dapper Erwin Schrodinger.

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And these sort of brash
20-year-olds, or mid-twenties,

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Werner Heisenberg
and Wolfgang Pauli.

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I had a huge version of
this photograph up on the wall

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as a poster in my college dorm room.

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My roommates had their favourite
bands, and I had the 1927

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Solvay Conference, which says a lot.

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This was one of the greatest
meetings of minds in history.

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More than half were or would become
Nobel Prize winners.

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Their experiments were showing
that deep inside matter,

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tiny particles, like atoms
and their orbiting electrons,

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were not solid little spheres.

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They seemed fuzzy and undefined.

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So this group here,

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these were the folks
who had just been plumbing deeper

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and deeper and deeper to find
what they hoped would be a bedrock

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of what the world is made of.

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And to their surprise, they found
things less and less solid

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as they dug in.

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This world was not tiny little
bricks that got smaller and smaller.

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At some point, the bricks
gave way to this mush.

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And what looked like solidity,
solidness, in fact became

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very confusing and
kind of a whole new way

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of thinking about nature.

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The theory of quantum mechanics

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presented at the meeting
was strange.

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It said that a particle like
an electron isn't physically real

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until it is observed
and measured by an instrument

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that can detect it.

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Before it's detected,

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instead of being a solid particle,

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an electron is just a fuzzy wave,

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a wave of probability.

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These objects,
like electrons and atoms,

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when we describe mathematically
their behaviour, the only thing

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we can describe is the probability
of being at one place or another.

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It's like a wave of all those
different possibilities.

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It's not that the electron
is in one place or the other,

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we just don't know,

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it's that the electron really is
a combination of

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every possible place it could be,

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until we look at it.

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Laws of nature were no longer
definite statements

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about what's going to happen next.

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They were just statements
about probabilities.

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And Einstein felt,
"Well, that's defeat.

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"You're giving up on the heart
of what physics has been,"

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namely to give a complete
description of reality.

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For Einstein, the idea that tiny
particles only pop into physical

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existence when they're observed
is akin to magic.

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He later asked a friend, "Do you
really believe the moon is not

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"there when you are not
looking at it?"

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Outside of the formal setting
of the conference...

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Bonsoir.

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..he challenged the most vocal
supporter of these ideas,

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the great Danish physicist
Niels Bohr.

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Einstein would show up to breakfast
at the hotel

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and Niels Bohr would be there,

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and Einstein would present
his latest challenge.

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Niels Bohr would sort of mumble
and wonder,

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and confer with
his younger colleagues.

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They'd head off to the formal
meeting at the Institute,

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and somehow, every night, by supper
time, Bohr would have an answer.

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One of the observers said that
Einstein was like a jack-in-the-box.

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Every day he'd pop up with
a new challenge and Bohr would flip

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this way and that, and then
by supper have crushed that one,

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and they would start all over again.

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To Bohr and his colleagues,

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quantum mechanics not only
explained experimental results,

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its mathematics were elegant
and beautiful.

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And since Einstein hadn't found
flaws in their equations, they left

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the Solvay Meeting feeling
more confident than ever

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in their ideas.

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But Einstein didn't give up.

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In 1933, Einstein, a Jewish
scientist and outspoken pacifist,

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fled Nazi Germany
and took a position at

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the Institute for Advanced Study
near Princeton.

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He recruited two physicists
to help him -

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Nathan Rosen and Boris Podolsky.

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And in 1935, at afternoon tea,
the three men formulated an idea

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that would shake the very
foundations of quantum theory.

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They discovered
quantum entanglement.

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Today, Robert Dijkgraaf is
the director of the institute.

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I think scientific progress is
often made in kind of a dialogue.

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And I think the informal
moments are crucial.

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So at the Institute
for Advanced Study,

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we've had tea at three o'clock
from the very beginning.

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It was here that a conversation
between Einstein and Rosen sparked

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a powerful idea.

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Rosen told him he was studying
a system of two hydrogen atoms,

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and noticed that there were
some ways in which

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these two atoms were coupled,

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even if you moved them very
far apart, and then apparently,

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Podolsky jumped in and said,
"Well, Professor Einstein,

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"this is very important
in your arguments showing

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"that quantum theory is incomplete."

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So they've got this very
animated discussion.

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And what's kind of happened still is
now you have a bunch of scientists

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discussing and at some point
someone says,

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"Let's write a paper together."
So they did.

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Their paper, known today as EPR,
argued that the equations of quantum

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mechanics predicted an impossible
connection between particles -

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a seemingly magical effect.

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It would be like having two
particles, each hidden from view.

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Looking at one...

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..mysteriously causes the other
to reveal itself too,

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with matching properties.

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Quantum theory suggested this effect
could happen in the real world.

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For example, with particles
of light - photons.

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The equations implied that a source
of photons could create pairs

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in such a way that when we measure
one, causing it to snap out

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of its fuzzy state,
the other mysteriously snaps

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out of its own fuzzy state
at the same instant,

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with correlated properties.

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The 1935 paper that described
this effect has become Einstein's

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most referenced work of all.

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It has captivated
generations of scientists,

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including one of the world's leading
quantum physicists,

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Professor Anton Zeilinger.

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The Einsten-Podolsky-Rosen Paper
fascinated me

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and I had to read it at least five
or six times until I finally

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understood what goes on,
and then it didn't let me go again.

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Another way to think of the paired
particles is to imagine a game

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of chance that's somehow rigged.

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Suppose I had a pair
of quantum dice.

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I put these two
quantum dice in my little cup.

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Throw them.

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I look at them.
They show the same number, six.

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I put them again in the cup.

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Throw them again.

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Now they both show three.

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I put them in again.

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Throw again.

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Now they both show one.

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The point now being, what I see
here is I see two random processes,

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namely each die showing some number,

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but these two random processes
do the same.

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That's really mind-boggling.

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How could two particles act
in unison,

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even when they're
separated from each other?

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Essential to the EPR argument
is that these particles

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can be can be separated
at an arbitrary distance -

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one could be here at Princeton, one
could be in the Andromeda galaxy.

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And yet, according to quantum
mechanics, a choice to measure

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something here is somehow
instantaneously affecting

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what can be said about
this other particle.

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You can't go from Princeton
to Andromeda instantly.

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And yet that, they argued,
is what the equations of quantum

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mechanics seem to imply, and that,
they said, so much the worse

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for quantum mechanics. The world
simply can't operate that way.

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For Einstein, this strange effect
conflicted with the most basic

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concept we use
to describe reality - space.

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For him, objects, particles,

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everything that exists
is located in space.

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Space, together with time,
was the key ingredient in his theory

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of special relativity,
with his famous equation,

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E = MC squared.

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Einstein, of course,
was the master of space time.

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He thought that if something
happened here, that shouldn't

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immediately and instantaneously
change something

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that is going on over there.

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The principle of locality,
as we currently call it.

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For Einstein, it's simply common
sense that if objects are separated

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in space, for one to affect
the other, something must

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travel between them.

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And that travelling takes time.

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Quantum particles acting
in unison could be explained

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if they were communicating.

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One particle instantly
sending a signal to the other,

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telling it what properties
it should have.

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But that would require
a signal travelling faster

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than the speed of light.

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Something Einstein's theory
of special relativity

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had proven impossible.

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And it would mean the particles
were fuzzy and undefined

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until the moment they were observed.

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00:15:59,540 --> 00:16:01,700
Instead, Einstein thought

248
00:16:01,700 --> 00:16:04,980
the particles should be real
all along.

249
00:16:04,980 --> 00:16:08,620
They must carry with them
a hidden layer of deeper physics

250
00:16:08,620 --> 00:16:11,700
that determines their properties
from the start.

251
00:16:13,580 --> 00:16:17,660
Almost the way that magic tricks,
while appearing mysterious,

252
00:16:17,660 --> 00:16:19,180
have a hidden explanation.

253
00:16:22,220 --> 00:16:25,980
But this hidden physics was missing
from quantum mechanics.

254
00:16:27,540 --> 00:16:29,820
So Einstein, Podolsky and Rosen

255
00:16:29,820 --> 00:16:32,820
argued that the theory
was incomplete.

256
00:16:35,380 --> 00:16:38,260
Podolsky was very enthusiastic
about this project.

257
00:16:38,260 --> 00:16:42,860
In fact, he was so enthusiastic
that he ran to the New York Times

258
00:16:42,860 --> 00:16:44,380
and told them the news.

259
00:16:44,380 --> 00:16:49,300
So Einstein read in the newspaper
that he has proven quantum theory

260
00:16:49,300 --> 00:16:51,700
is incomplete and possibly wrong,

261
00:16:51,700 --> 00:16:54,100
and he was very much upset by that.

262
00:16:54,100 --> 00:16:57,340
So he writes a letter to the editor
saying, "This is not the way one

263
00:16:57,340 --> 00:16:59,500
"should communicate in physics."

264
00:16:59,500 --> 00:17:02,580
And he was really upset
with Podolsky.

265
00:17:02,580 --> 00:17:05,260
Apparently he didn't speak
to him any more.

266
00:17:06,860 --> 00:17:10,060
When Niels Bohr heard
of Einstein's paper,

267
00:17:10,060 --> 00:17:14,380
he wrote an obscure response,
arguing that one particle

268
00:17:14,380 --> 00:17:16,820
could instantly influence another.

269
00:17:18,700 --> 00:17:22,140
This seemingly
impossible phenomenon

270
00:17:22,140 --> 00:17:25,140
became known as
quantum entanglement.

271
00:17:28,220 --> 00:17:32,420
But Einstein dismissed it as
"spooky action at a distance".

272
00:17:34,860 --> 00:17:38,100
No-one can think of an experiment
to test whether Einstein

273
00:17:38,100 --> 00:17:39,820
or Bohr was correct.

274
00:17:41,660 --> 00:17:44,860
But that didn't stop physicists
and engineers from making use

275
00:17:44,860 --> 00:17:47,540
of quantum mechanics in the lab.

276
00:17:50,100 --> 00:17:52,620
In the '30s and '40s, the debate

277
00:17:52,620 --> 00:17:55,780
around the EPR Paper
sort of dies down,

278
00:17:55,780 --> 00:17:58,260
but quantum theory
actually takes off.

279
00:18:00,780 --> 00:18:04,740
The mathematics leads to all kinds
of amazing developments.

280
00:18:06,140 --> 00:18:10,620
The equations of quantum mechanics
accurately predict the behaviour

281
00:18:10,620 --> 00:18:14,460
of atoms and tiny particles,
enabling the scientists

282
00:18:14,460 --> 00:18:18,180
of the Manhattan Project
to develop the bomb.

283
00:18:20,220 --> 00:18:24,940
And in the years after the Second
World War, researchers at Bell Labs

284
00:18:24,940 --> 00:18:29,940
in New Jersey used quantum theory
to develop the first lasers.

285
00:18:29,940 --> 00:18:33,620
In our laboratories, men experiment
with a light once undreamed of

286
00:18:33,620 --> 00:18:35,260
in the natural world.

287
00:18:35,260 --> 00:18:39,540
And build small devices that could
control the flow of electricity -

288
00:18:39,540 --> 00:18:41,380
transistors.

289
00:18:41,380 --> 00:18:44,220
It's destined to play a vital role
in your future.

290
00:18:44,220 --> 00:18:46,620
Your electronic future.

291
00:18:46,620 --> 00:18:48,860
Transistors became
the building blocks

292
00:18:48,860 --> 00:18:51,100
of the burgeoning field
of electronics.

293
00:18:51,100 --> 00:18:56,260
Computers, disc drives, the entire
digital revolution, soon followed.

294
00:18:57,340 --> 00:19:01,020
All made possible by the equations
of quantum theory.

295
00:19:02,700 --> 00:19:06,500
Yet Einstein's questions
about entanglement and what it

296
00:19:06,500 --> 00:19:10,820
implied about the incompleteness
of quantum mechanics remained

297
00:19:10,820 --> 00:19:13,420
unanswered until the 1960s...

298
00:19:15,220 --> 00:19:17,820
..when a physicist from
Northern Ireland

299
00:19:17,820 --> 00:19:21,180
made a remarkable breakthrough -
John Bell.

300
00:19:21,180 --> 00:19:25,060
Bell was a very talented
young physics student,

301
00:19:25,060 --> 00:19:27,540
but he quickly grew dissatisfied
with what he considered

302
00:19:27,540 --> 00:19:29,940
almost a kind of dishonesty
among his teachers.

303
00:19:29,940 --> 00:19:34,940
Bell insisted that Einstein's
questions about quantum mechanics

304
00:19:34,940 --> 00:19:37,180
had not been addressed.

305
00:19:37,180 --> 00:19:39,660
He got into shouting matches
with his professors.

306
00:19:39,660 --> 00:19:42,060
"Don't tell us that Bohr
solved all the problems.

307
00:19:42,060 --> 00:19:44,460
"This really deserves
further thought."

308
00:19:44,460 --> 00:19:48,660
Quantum mechanics
has been fantastically successful.

309
00:19:48,660 --> 00:19:51,500
So it is a very intriguing
situation.

310
00:19:51,500 --> 00:19:56,700
At the foundation of all
that impressive success,

311
00:19:56,700 --> 00:19:59,260
there are these great doubts.

312
00:20:01,900 --> 00:20:06,700
It's a very strange thing that ever
since the 1930s, the idea of sitting

313
00:20:06,700 --> 00:20:09,460
and thinking hard about the
foundations of quantum mechanics

314
00:20:09,460 --> 00:20:12,340
has been disreputable among
professional physicists.

315
00:20:12,340 --> 00:20:14,980
When people tried to do that,
they were kicked out

316
00:20:14,980 --> 00:20:16,380
of physics departments.

317
00:20:16,380 --> 00:20:20,140
And so, for someone like Bell,
he needed to have a day job doing

318
00:20:20,140 --> 00:20:21,860
ordinary particle physics.

319
00:20:21,860 --> 00:20:23,620
But at night, you know, hidden away,

320
00:20:23,620 --> 00:20:26,340
he could do work on the foundations
of quantum mechanics.

321
00:20:26,340 --> 00:20:31,660
Bell became a leading particle
physicist at CERN in Geneva,

322
00:20:31,660 --> 00:20:36,100
but he continued to explore the
debate between Einstein and Bohr.

323
00:20:37,780 --> 00:20:41,420
And in 1964, he published
an astonishing paper.

324
00:20:43,420 --> 00:20:46,820
Bell proved that
Bohr's and Einstein's ideas

325
00:20:46,820 --> 00:20:48,700
made different predictions.

326
00:20:50,980 --> 00:20:55,500
If you could randomly perform one
of two possible measurements

327
00:20:55,500 --> 00:20:59,500
on each particle and check
how often the results lined up,

328
00:20:59,500 --> 00:21:04,220
the answer would reveal whether
we lived in Einstein's world,

329
00:21:04,220 --> 00:21:07,980
the world that followed
common-sense laws,

330
00:21:07,980 --> 00:21:09,780
or Bohr's,

331
00:21:09,780 --> 00:21:12,780
a world that was deeply strange,

332
00:21:12,780 --> 00:21:15,300
and allows
spooky quantum connections.

333
00:21:16,900 --> 00:21:18,340
We now know, with hindsight,

334
00:21:18,340 --> 00:21:21,420
this was one of the most significant
articles in the history of physics,

335
00:21:21,420 --> 00:21:23,460
not just the history of
20th-century physics -

336
00:21:23,460 --> 00:21:26,100
in the history
of the field as a whole.

337
00:21:28,020 --> 00:21:31,460
But Bell's article appears in this,
you know, sort of out of the way

338
00:21:31,460 --> 00:21:34,180
journal, in fact, the journal itself
folds a few years later.

339
00:21:34,180 --> 00:21:36,620
This is not central to
the physics community.

340
00:21:36,620 --> 00:21:39,100
It's sort of dutifully filed
on library shelves,

341
00:21:39,100 --> 00:21:40,700
and then forgotten.

342
00:21:40,700 --> 00:21:42,740
It literally collects dust
on the shelf.

343
00:21:44,740 --> 00:21:49,340
A few years later, completely
by chance, a brilliant experimental

344
00:21:49,340 --> 00:21:52,060
physicist stumbled upon
Bell's article.

345
00:21:53,620 --> 00:21:57,580
I thought, "This is one of the most
amazing papers I had ever read

346
00:21:57,580 --> 00:21:59,900
"in my whole life."

347
00:21:59,900 --> 00:22:03,540
And I kept wondering,
"Well, gee, this is wonderful.

348
00:22:03,540 --> 00:22:06,660
"But where's the experimental
evidence?"

349
00:22:10,540 --> 00:22:15,660
At the University of California,
Berkeley, John Clauser was desperate

350
00:22:15,660 --> 00:22:19,100
to put Bell's idea to the test
in an experiment.

351
00:22:20,260 --> 00:22:22,140
He had a talent for tinkering
in the lab

352
00:22:22,140 --> 00:22:24,060
and building the parts he needed.

353
00:22:24,060 --> 00:22:28,020
I used to rummage around here
and scavenge,

354
00:22:28,020 --> 00:22:29,980
and dumpster dive for old equipment.

355
00:22:29,980 --> 00:22:35,260
He knew where to find hidden storage
rooms like this, which he could raid

356
00:22:35,260 --> 00:22:38,700
to salvage spare parts
for his experiments.

357
00:22:43,220 --> 00:22:47,220
This was a power supply
for diode lasers.

358
00:22:47,220 --> 00:22:49,340
That looks like something I built.

359
00:22:52,460 --> 00:22:55,460
This is wonderful.
This is my book.

360
00:22:55,460 --> 00:22:56,900
I think this may be my old book.

361
00:23:01,220 --> 00:23:02,580
I'll take it!

362
00:23:07,100 --> 00:23:10,820
Deep in the basement
is John's old laboratory.

363
00:23:10,820 --> 00:23:14,100
This is B207, where we did
the original experiment.

364
00:23:16,980 --> 00:23:20,260
He hasn't been back for decades.

365
00:23:20,260 --> 00:23:24,020
I remember distinctly
this old sink.

366
00:23:24,020 --> 00:23:27,980
These computers
were not yet invented.

367
00:23:27,980 --> 00:23:29,940
It was hard work -

368
00:23:29,940 --> 00:23:33,300
we spent long hours, weekends,
evenings, you name it.

369
00:23:33,300 --> 00:23:36,300
We believed, although nobody else
did, that it was actually

370
00:23:36,300 --> 00:23:39,140
a very significant and important
experiment.

371
00:23:54,580 --> 00:23:55,940
Careful!

372
00:23:57,220 --> 00:23:58,660
Where is this?

373
00:23:58,660 --> 00:24:01,220
So this is my shop,

374
00:24:01,220 --> 00:24:03,940
and laboratory.

375
00:24:03,940 --> 00:24:08,260
Mostly now, I just build sailboat
parts for yacht racing.

376
00:24:13,100 --> 00:24:15,660
Here's a picture
of the experiment I did.

377
00:24:15,660 --> 00:24:18,220
I had more hair in those days!

378
00:24:19,380 --> 00:24:22,660
Here's another picture.
This is Stuart Freedman.

379
00:24:22,660 --> 00:24:24,620
Worked on it with me.

380
00:24:24,620 --> 00:24:28,300
Two photons, entangled photons
would go out

381
00:24:28,300 --> 00:24:32,540
in the opposite directions
through lenses into the polarizers.

382
00:24:32,540 --> 00:24:35,900
They could be, in the simplest
case, we'd put the lenses

383
00:24:35,900 --> 00:24:38,340
in Polaroid sunglasses.

384
00:24:39,620 --> 00:24:42,700
John Clauser and Stuart Freedman
constructed

385
00:24:42,700 --> 00:24:45,500
the world's first Bell Test
experiment.

386
00:24:46,780 --> 00:24:50,740
They focused a laser onto
calcium atoms,

387
00:24:50,740 --> 00:24:52,980
creating pairs of photons

388
00:24:52,980 --> 00:24:57,460
that the equations of quantum theory
suggested should be entangled.

389
00:24:59,500 --> 00:25:02,180
They recorded whether or not
the photons passed through

390
00:25:02,180 --> 00:25:06,900
polarisation filters on
each side, and checked how often

391
00:25:06,900 --> 00:25:09,700
the answers agreed.

392
00:25:09,700 --> 00:25:11,700
After thousands of pairs,

393
00:25:11,700 --> 00:25:16,260
if the results were more correlated
than Einstein's physics predicted,

394
00:25:16,260 --> 00:25:19,660
the photons must be
spookily entangled.

395
00:25:22,340 --> 00:25:25,860
We saw the stronger correlation,
characteristic of quantum mechanics.

396
00:25:25,860 --> 00:25:29,780
We measured it
and that's what we got.

397
00:25:31,340 --> 00:25:36,340
The outcome was exactly what Bohr's
quantum mechanics predicted.

398
00:25:36,340 --> 00:25:40,260
The experiment appeared to show
that the spooky connections

399
00:25:40,260 --> 00:25:44,420
of quantum entanglement
did exist in the natural world.

400
00:25:46,180 --> 00:25:49,460
Could it be that the great
Albert Einstein was wrong?

401
00:25:54,660 --> 00:25:58,180
The first people to react
to this extraordinary result

402
00:25:58,180 --> 00:26:00,620
were not the world's
leading physicists.

403
00:26:05,580 --> 00:26:08,540
Ronald Reagan's definition
of a hippie

404
00:26:08,540 --> 00:26:13,380
was someone who dresses
like Tarzan, has hair like Jane

405
00:26:13,380 --> 00:26:15,340
and smells like Cheeta.

406
00:26:19,820 --> 00:26:23,420
A small group of freethinking
physicists at the heart

407
00:26:23,420 --> 00:26:27,580
of San Francisco's New Age scene
got in touch with John.

408
00:26:30,140 --> 00:26:32,620
They call themselves
the Fundamental Fysics Group.

409
00:26:32,620 --> 00:26:34,060
They spelled physics with an F.

410
00:26:34,060 --> 00:26:36,740
Some members would experiment
with psychedelic drugs.

411
00:26:36,740 --> 00:26:40,580
I mean, they were kind of in the
flow of the kind of hippie scene.

412
00:26:40,580 --> 00:26:44,060
And that group was just mesmerised
by the question of entanglement.

413
00:26:46,660 --> 00:26:51,260
The idea was just to discuss
fringe subjects with an open mind

414
00:26:51,260 --> 00:26:54,580
and I thought, "Well, sure,
that's kind of what I do."

415
00:26:56,460 --> 00:27:00,620
They were doing their best
to link Eastern mysticism

416
00:27:00,620 --> 00:27:02,420
with quantum entanglement.

417
00:27:03,700 --> 00:27:06,340
They sold a lot of
popular textbooks.

418
00:27:06,340 --> 00:27:08,780
There were a lot of followers.

419
00:27:08,780 --> 00:27:12,980
Their books became bestsellers,
like The Tao of Physics,

420
00:27:12,980 --> 00:27:17,380
which highlighted that Eastern
philosophy and quantum entanglement

421
00:27:17,380 --> 00:27:22,740
both described a deep connectedness
of things in the universe.

422
00:27:22,740 --> 00:27:24,980
The Great Cosmic Oneness.

423
00:27:24,980 --> 00:27:29,620
The group held meetings
at the iconic Esalen Institute.

424
00:27:30,900 --> 00:27:34,340
It was a marvellous, beautiful place
where they would discuss

425
00:27:34,340 --> 00:27:35,900
all of these ideas.

426
00:27:35,900 --> 00:27:40,460
It was right on the Pacific coast
with the overflow from the hot tubs

427
00:27:40,460 --> 00:27:43,940
cascading down the cliffs
into the Pacific Ocean.

428
00:27:45,180 --> 00:27:50,420
To my knowledge, no useful
connections to Eastern mysticism

429
00:27:50,420 --> 00:27:52,420
were ever discovered by the group.

430
00:27:55,100 --> 00:27:56,740
But it was fun!

431
00:27:57,980 --> 00:28:01,980
The Fundamental Fysics Group
may not have uncovered the secrets

432
00:28:01,980 --> 00:28:07,380
of cosmic oneness, but in seeing
entanglement as central to physics,

433
00:28:07,380 --> 00:28:09,980
they were decades ahead
of their time.

434
00:28:15,220 --> 00:28:19,500
In the years after Clauser
and Freedman's pioneering work,

435
00:28:19,500 --> 00:28:23,140
physicists began to test possible
loopholes in their experiment.

436
00:28:25,020 --> 00:28:29,740
Ways in which the illusion
of entanglement may be created

437
00:28:29,740 --> 00:28:33,900
so the effect might not be
so spooky after all.

438
00:28:33,900 --> 00:28:37,900
One loophole
is especially hard to rule out.

439
00:28:39,100 --> 00:28:43,500
In modern Bell Test experiments,
devices at each side test

440
00:28:43,500 --> 00:28:47,580
whether the photons can pass
through one of two filters

441
00:28:47,580 --> 00:28:49,620
that are randomly chosen,

442
00:28:49,620 --> 00:28:52,980
effectively asking one of
two questions

443
00:28:52,980 --> 00:28:56,620
and checking how often
the answers agree.

444
00:28:56,620 --> 00:28:58,820
After thousands of photons,

445
00:28:58,820 --> 00:29:00,420
if the results line up

446
00:29:00,420 --> 00:29:04,820
more than Einstein's physics
predicts, the particles

447
00:29:04,820 --> 00:29:06,780
must be spookily entangled.

448
00:29:08,820 --> 00:29:10,500
But what if something had

449
00:29:10,500 --> 00:29:13,580
mysteriously influenced
the equipment

450
00:29:13,580 --> 00:29:16,900
so that the choices of the filters
were not truly random?

451
00:29:18,900 --> 00:29:22,860
Is there any common cause, deep
in the past before you even turn

452
00:29:22,860 --> 00:29:25,900
on your device, that could
have nudged the questions

453
00:29:25,900 --> 00:29:28,660
to be asked and the types of
particles to be emitted?

454
00:29:28,660 --> 00:29:32,580
Maybe some strange particle, maybe
some force that had not been taken

455
00:29:32,580 --> 00:29:35,460
into account, so that what looks
like entanglement might indeed

456
00:29:35,460 --> 00:29:37,500
be an accident, an illusion.

457
00:29:37,500 --> 00:29:40,660
Maybe the world still acts
like Einstein thought.

458
00:29:45,940 --> 00:29:50,900
It's this loophole that the team
of Austrian and American physicists

459
00:29:50,900 --> 00:29:55,380
is working to tackle at the high
altitude observatory on the island

460
00:29:55,380 --> 00:29:58,260
of La Palma in the Canaries.

461
00:29:58,260 --> 00:30:00,300
With quantum mechanics

462
00:30:00,300 --> 00:30:03,300
now more established than ever,
they're determined to put

463
00:30:03,300 --> 00:30:05,420
entanglement to the ultimate test,

464
00:30:05,420 --> 00:30:08,300
and finally settle
the Einstein-Bohr debate

465
00:30:08,300 --> 00:30:10,620
beyond all reasonable doubt.

466
00:30:15,260 --> 00:30:17,940
Professor Anton Zeilinger
is leading the team.

467
00:30:20,300 --> 00:30:26,460
So we are now going up the mountain
towards the Roque de los Muchachos.

468
00:30:28,420 --> 00:30:30,460
Everything looks perfect today.

469
00:30:33,140 --> 00:30:35,540
They're creating a giant
version of Clauser and

470
00:30:35,540 --> 00:30:38,700
Freedman's Bell Test,
with the entire universe

471
00:30:38,700 --> 00:30:40,380
as their lab bench.

472
00:30:45,460 --> 00:30:50,900
In this cosmic Bell Test, the source
of the entangled particles is almost

473
00:30:50,900 --> 00:30:54,780
exactly 500 metres from each
of the two telescopes.

474
00:30:56,100 --> 00:31:00,380
The team must send perfectly timed
pairs of photons through the air

475
00:31:00,380 --> 00:31:02,500
to each side.

476
00:31:02,500 --> 00:31:04,660
At the same time,

477
00:31:04,660 --> 00:31:08,460
the telescopes will collect
light from two extremely far off,

478
00:31:08,460 --> 00:31:11,300
extremely bright galaxies
called quasars.

479
00:31:12,780 --> 00:31:16,780
Random variations in the colour
of the quasar light will determine

480
00:31:16,780 --> 00:31:20,660
which filters the photons
must pass through.

481
00:31:20,660 --> 00:31:23,580
And since the light from the quasars
has been travelling

482
00:31:23,580 --> 00:31:26,180
for billions of years
to reach Earth,

483
00:31:26,180 --> 00:31:28,980
it makes it incredibly unlikely
that anything

484
00:31:28,980 --> 00:31:32,140
could be influencing the random
nature of the test.

485
00:31:33,780 --> 00:31:37,500
At this experiment,
we use three locations.

486
00:31:37,500 --> 00:31:40,660
One is behind me here,

487
00:31:40,660 --> 00:31:44,220
where you see this container
with the blue frame.

488
00:31:44,220 --> 00:31:49,500
In that container we have the source
for the entangled pairs of photons.

489
00:31:49,500 --> 00:31:52,980
One of the two photons is sent
to one telescope,

490
00:31:52,980 --> 00:31:54,700
the other one to the other.

491
00:31:54,700 --> 00:31:56,620
The first telescope is here.

492
00:31:56,620 --> 00:32:02,020
The Telescopio Nazionale Galileo.

493
00:32:02,020 --> 00:32:05,300
It's an Italian telescope.

494
00:32:05,300 --> 00:32:08,620
You can see the small container
on the bridge there

495
00:32:08,620 --> 00:32:10,900
where the photon arrives.

496
00:32:10,900 --> 00:32:16,020
And the telescope then will look up
on the sky, pick up the light

497
00:32:16,020 --> 00:32:21,820
from a quasar, which is very, very
far away, and take the signal

498
00:32:21,820 --> 00:32:27,140
of the quasar to steer the kind
of measurement done on the photon

499
00:32:27,140 --> 00:32:28,580
which arrives.

500
00:32:28,580 --> 00:32:33,700
Over there is Herschel - William
Herschel telescope, the big one.

501
00:32:33,700 --> 00:32:35,620
The photon arrives there,

502
00:32:35,620 --> 00:32:37,940
and again, that telescope picks up

503
00:32:37,940 --> 00:32:40,300
the light from
a different quasar,

504
00:32:40,300 --> 00:32:43,740
and that steers the measurement
on the photon here.

505
00:32:46,580 --> 00:32:50,660
The preparation right now
is that at the source,

506
00:32:50,660 --> 00:32:53,580
I would claim that we have some
of the best people in the world

507
00:32:53,580 --> 00:32:56,140
working on these quantum sources.

508
00:32:56,140 --> 00:33:00,700
By firing a laser through
a specially made crystal,

509
00:33:00,700 --> 00:33:02,420
the team creates a pair of photons

510
00:33:02,420 --> 00:33:06,420
that quantum theory suggests
should be entangled.

511
00:33:06,420 --> 00:33:10,660
We have some entanglement,
just about the best we've seen here.

512
00:33:10,660 --> 00:33:14,260
We still have to tune the state
a bit to get to what we usually

513
00:33:14,260 --> 00:33:16,260
achieve in the lab.

514
00:33:16,260 --> 00:33:19,500
Then the next step also
being done in daylight now

515
00:33:19,500 --> 00:33:22,500
is to try to couple the two
positions to each other

516
00:33:22,500 --> 00:33:25,500
with lasers, to make sure
that they really see each other,

517
00:33:25,500 --> 00:33:26,860
that everything works.

518
00:33:30,020 --> 00:33:31,260
OK.

519
00:33:31,260 --> 00:33:35,180
Eins, zwei, drei, vier, funf...

520
00:33:35,180 --> 00:33:36,500
OK.

521
00:33:36,500 --> 00:33:40,620
And also in parallel,
they are making big lists

522
00:33:40,620 --> 00:33:42,420
of possible quasars.

523
00:33:42,420 --> 00:33:44,740
This is our favourite pair
of quasars.

524
00:33:44,740 --> 00:33:49,620
One of the quasars emitted its light
something like 12 billion years ago.

525
00:33:49,620 --> 00:33:53,060
The William Herschel Telescope
is going to look at a quasar that's

526
00:33:53,060 --> 00:33:54,420
coming up from the horizon

527
00:33:54,420 --> 00:33:56,740
throughout our two-hour
observation period,

528
00:33:56,740 --> 00:33:58,580
getting higher and higher
in the sky.

529
00:33:58,580 --> 00:34:01,460
Galileo Telescope is going to look
at this other quasar that's

530
00:34:01,460 --> 00:34:03,420
sweeping out on the sky.

531
00:34:03,420 --> 00:34:06,220
In the end, it could be
running smoothly,

532
00:34:06,220 --> 00:34:08,700
or there will need to be

533
00:34:08,700 --> 00:34:12,740
a couple of decisions made,
you know, in an excited state,

534
00:34:12,740 --> 00:34:14,620
in the last instance.

535
00:34:21,020 --> 00:34:25,180
With the experiment finally set up,
the team take their positions.

536
00:34:28,020 --> 00:34:29,740
Professor David Kaiser has worked

537
00:34:29,740 --> 00:34:32,460
on this experiment
with his colleague

538
00:34:32,460 --> 00:34:36,260
Jason Gallicchio for four years.

539
00:34:36,260 --> 00:34:39,820
Coordinating it all
is Dominik Rauch.

540
00:34:39,820 --> 00:34:42,540
The experiment is his
thesis project.

541
00:34:42,540 --> 00:34:45,580
He's also been preparing for years.

542
00:34:47,420 --> 00:34:51,420
But as darkness falls, temperatures
on the mountain begin to drop.

543
00:34:58,300 --> 00:34:59,540
OK.

544
00:35:01,580 --> 00:35:03,300
OK. There's bad news.

545
00:35:03,300 --> 00:35:05,460
They have been told to leave
the William Herschel

546
00:35:05,460 --> 00:35:08,100
because the road will be
so dangerous, too dangerous.

547
00:35:08,100 --> 00:35:09,980
So they have to go down now.

548
00:35:09,980 --> 00:35:11,420
Yeah.

549
00:35:13,380 --> 00:35:17,500
The team has been instructed
to leave the telescopes.

550
00:35:17,500 --> 00:35:19,780
The extreme weather could
quickly make their route

551
00:35:19,780 --> 00:35:22,660
off the mountain too dangerous.

552
00:35:22,660 --> 00:35:25,260
After all the preparation,

553
00:35:25,260 --> 00:35:27,220
it's devastating news.

554
00:35:30,380 --> 00:35:35,380
Yes. There seems to be a serious
ice problem on the road.

555
00:35:35,380 --> 00:35:36,860
OK.

556
00:35:36,860 --> 00:35:43,300
We'll be called back if things
work out, I guess. Happens. Yeah.

557
00:35:43,300 --> 00:35:44,500
What can you do?

558
00:36:02,740 --> 00:36:07,060
The next day, the team begins
to prepare for another attempt.

559
00:36:23,660 --> 00:36:25,980
As the sun begins to set,

560
00:36:25,980 --> 00:36:29,620
and the experiment's
start time approaches,

561
00:36:29,620 --> 00:36:33,660
Johannes Handsteiner checks
the equipment hasn't been affected

562
00:36:33,660 --> 00:36:35,180
by the weather.

563
00:36:42,460 --> 00:36:44,180
What are you doing, Johnny?

564
00:36:44,180 --> 00:36:46,900
I'm currently checking the signals

565
00:36:46,900 --> 00:36:50,940
from the cosmic random number
generator,

566
00:36:50,940 --> 00:36:53,220
checking if we have
a high enough signal,

567
00:36:53,220 --> 00:36:56,380
and it looks pretty good.

568
00:37:00,500 --> 00:37:03,540
But now, the air is thick
with clouds.

569
00:37:14,620 --> 00:37:17,180
Here's the humidity
at the various telescopes,

570
00:37:17,180 --> 00:37:20,660
and you see the humidity
is 100%.

571
00:37:20,660 --> 00:37:23,220
So as long as this lasts...

572
00:37:24,700 --> 00:37:26,140
..we can't do much.

573
00:37:32,860 --> 00:37:35,020
The teams at both telescopes wait.

574
00:37:38,380 --> 00:37:40,180
But the clouds don't clear.

575
00:37:43,340 --> 00:37:46,580
All the preparation
has come to nothing.

576
00:37:46,580 --> 00:37:51,020
Time on these huge telescopes
is precious and theirs has run out.

577
00:37:53,380 --> 00:37:57,620
This ambitious test of
quantum entanglement must wait.

578
00:38:00,900 --> 00:38:05,380
Anton Zeilinger was first captivated
by the concept of entanglement

579
00:38:05,380 --> 00:38:08,980
as a young researcher in the 1980s.

580
00:38:08,980 --> 00:38:14,660
I did not go to a single hour at the
University of Quantum Mechanics.

581
00:38:14,660 --> 00:38:16,540
I learned it all from books.

582
00:38:17,940 --> 00:38:21,380
And when I read the books,

583
00:38:21,380 --> 00:38:27,380
it was clear that people evaded
the question, what does it mean?

584
00:38:27,380 --> 00:38:31,860
They pretended everything is clear,
but it was not so clear.

585
00:38:31,860 --> 00:38:33,940
The mathematics is fantastic.

586
00:38:33,940 --> 00:38:38,220
It's so beautiful that one can only
regret that not everybody

587
00:38:38,220 --> 00:38:40,500
can appreciate it.

588
00:38:40,500 --> 00:38:42,300
But what the heck is behind it?

589
00:38:43,700 --> 00:38:47,940
Anton began to experiment
with entanglement in the lab.

590
00:38:47,940 --> 00:38:50,180
As new technologies developed,

591
00:38:50,180 --> 00:38:54,060
he was able to perform
remarkable quantum trickery.

592
00:38:54,060 --> 00:38:57,700
What happens if, instead of
two particles, you have three?

593
00:38:57,700 --> 00:38:59,260
Nobody knew.

594
00:39:01,620 --> 00:39:05,500
And it was my goal from then on
to realise that in the lab,

595
00:39:05,500 --> 00:39:09,020
and he took me ten years
until I had that.

596
00:39:16,780 --> 00:39:21,780
What at that time we could do
was create pairs

597
00:39:21,780 --> 00:39:23,300
of entangled particles.

598
00:39:23,300 --> 00:39:27,180
So you have a pair and another pair.

599
00:39:27,180 --> 00:39:33,020
And then, what you do
is you kind of mix

600
00:39:33,020 --> 00:39:34,420
these two photons.

601
00:39:35,780 --> 00:39:41,780
Mix these two photons,
and take one out of the system,

602
00:39:41,780 --> 00:39:47,980
and then you are left with
one, two, three, one, two, three.

603
00:39:47,980 --> 00:39:52,180
And if you do it right,
then this this photon doesn't know

604
00:39:52,180 --> 00:39:55,380
whether it belongs to this partner
or this partner.

605
00:39:55,380 --> 00:39:58,860
And that way, all three
become entangled.

606
00:40:03,300 --> 00:40:07,620
Today, cutting-edge labs
around the world are racing

607
00:40:07,620 --> 00:40:10,620
to harness Anton's
multi-particle entanglement

608
00:40:10,620 --> 00:40:14,420
to create revolutionary
new technologies.

609
00:40:17,100 --> 00:40:18,860
Like quantum computers.

610
00:40:22,220 --> 00:40:26,740
In our everyday computers,
the fundamental unit of computing

611
00:40:26,740 --> 00:40:29,620
is a bit - a binary digit,
zero or one.

612
00:40:29,620 --> 00:40:32,140
And inside the computer,
there's all these transistors

613
00:40:32,140 --> 00:40:34,380
which are turning on and off
currents.

614
00:40:34,380 --> 00:40:36,620
On is one, off is zero.

615
00:40:36,620 --> 00:40:40,140
And these combinations lead
to universal computing.

616
00:40:40,140 --> 00:40:41,660
With a quantum computer,

617
00:40:41,660 --> 00:40:45,420
you start with the fundamental unit
that's not a bit, but a quantum bit,

618
00:40:45,420 --> 00:40:49,300
which is not really a zero or a one,
but it can be fluid.

619
00:40:50,900 --> 00:40:54,460
A quantum bit makes use
of the fuzziness

620
00:40:54,460 --> 00:40:56,900
of the quantum world.

621
00:40:56,900 --> 00:40:58,620
A qubit, as it's known,

622
00:40:58,620 --> 00:41:02,020
can be a zero or one,
or a combination of both.

623
00:41:02,020 --> 00:41:07,060
A particle or tiny quantum system
can be made into a qubit.

624
00:41:08,220 --> 00:41:11,580
And groups of qubits can be linked
with entanglement

625
00:41:11,580 --> 00:41:14,540
to create a quantum computer.

626
00:41:14,540 --> 00:41:18,420
The more qubits, the greater
the processing power.

627
00:41:21,020 --> 00:41:24,980
At Google's Quantum Computing
Laboratory in Santa Barbara,

628
00:41:24,980 --> 00:41:30,060
the team has recently created
a single chip that holds 72 qubits,

629
00:41:30,060 --> 00:41:33,860
more than any other
quantum chip produced to date.

630
00:41:36,140 --> 00:41:39,860
The task for researcher
Marissa Giustina and her colleagues

631
00:41:39,860 --> 00:41:43,620
is to send signals
to these microscopic qubits

632
00:41:43,620 --> 00:41:45,860
to control and entangle them.

633
00:41:49,060 --> 00:41:52,380
Mounted on the underside
of this plate, we have the quantum

634
00:41:52,380 --> 00:41:54,500
processing chip itself.

635
00:41:54,500 --> 00:41:56,580
In essence, a quantum playground,

636
00:41:56,580 --> 00:42:00,140
you could say. Each qubit
is a quantum object

637
00:42:00,140 --> 00:42:03,540
that we should be able
to control at will.

638
00:42:03,540 --> 00:42:09,140
Thinking about it as the faster
version of that PC over there

639
00:42:09,140 --> 00:42:12,260
would be a great slight to this.

640
00:42:12,260 --> 00:42:14,380
It can be much more than that.

641
00:42:14,380 --> 00:42:17,300
For instance, if we want
to understand how some chemical

642
00:42:17,300 --> 00:42:21,740
reaction works, rather than using
a mathematical model, we can use

643
00:42:21,740 --> 00:42:24,980
these qubits to model the chemistry.

644
00:42:26,620 --> 00:42:29,300
By using entangled qubits,

645
00:42:29,300 --> 00:42:32,740
quantum computers could tackle
real world problems

646
00:42:32,740 --> 00:42:36,220
that traditional computers
simply can't cope with.

647
00:42:37,540 --> 00:42:39,820
For example -

648
00:42:39,820 --> 00:42:42,580
a salesman has to travel
to several cities,

649
00:42:42,580 --> 00:42:44,980
and wants to find
the shortest route.

650
00:42:46,380 --> 00:42:48,780
Sounds easy.

651
00:42:48,780 --> 00:42:52,700
But with just 30 cities,
there are so many possible routes,

652
00:42:52,700 --> 00:42:56,060
it would take an ordinary computer,
even a powerful one,

653
00:42:56,060 --> 00:43:00,220
hundreds of years to try each one
and find the shortest.

654
00:43:02,060 --> 00:43:06,180
But with a handful of entangled
qubits, a quantum computer

655
00:43:06,180 --> 00:43:08,300
could resolve the optimal path

656
00:43:08,300 --> 00:43:10,380
in a fraction of the number
of steps.

657
00:43:13,860 --> 00:43:17,700
There's another reason teams
like Marissa's are racing to create

658
00:43:17,700 --> 00:43:19,500
a powerful quantum computer.

659
00:43:20,860 --> 00:43:22,700
Cracking secret codes.

660
00:43:25,020 --> 00:43:29,660
In today's world, everything
from online shopping to covert

661
00:43:29,660 --> 00:43:33,420
military communications
is protected from hackers

662
00:43:33,420 --> 00:43:37,860
using secure digital codes,
a process called encryption.

663
00:43:40,140 --> 00:43:44,380
But what if hackers could make use
of quantum computers?

664
00:43:44,380 --> 00:43:46,780
A quantum computer could crack

665
00:43:46,780 --> 00:43:49,860
our best encryption protocols
in minutes,

666
00:43:49,860 --> 00:43:53,620
whereas a regular computer or even
a supercomputing network today

667
00:43:53,620 --> 00:43:56,340
couldn't do it,
you know, given months of time.

668
00:43:56,340 --> 00:44:00,580
But while quantum entanglement
may be a threat to traditional

669
00:44:00,580 --> 00:44:05,460
encryption, it also offers an even
more secure alternative.

670
00:44:07,860 --> 00:44:11,660
A communication system that
the very laws of physics protect

671
00:44:11,660 --> 00:44:13,180
from secret hacking.

672
00:44:17,620 --> 00:44:20,460
Researchers in China
are leading the way.

673
00:44:23,900 --> 00:44:28,820
Here in Shanghai, at the University
of Science and Technology,

674
00:44:28,820 --> 00:44:33,140
Professor Jian-Wei Pan runs
a leading quantum research centre.

675
00:44:34,860 --> 00:44:38,100
His teams are working to harness
the properties of the quantum world.

676
00:44:40,540 --> 00:44:42,700
They can send secret messages

677
00:44:42,700 --> 00:44:45,460
using a stream of photons
in a system

678
00:44:45,460 --> 00:44:49,620
that instantly detects any attempt
to steal the information.

679
00:44:53,220 --> 00:44:55,420
Including digital phone calls

680
00:44:55,420 --> 00:45:00,420
that, in theory, are impossible
to hack into.

681
00:45:00,420 --> 00:45:02,660
So what have we got in here?

682
00:45:02,660 --> 00:45:06,180
So here is a system for
the secure telephone, yeah?

683
00:45:06,180 --> 00:45:10,540
This is a fibre connection
between two systems,

684
00:45:10,540 --> 00:45:13,020
to send secure information.

685
00:45:17,940 --> 00:45:19,940
PHONE RINGS

686
00:45:22,180 --> 00:45:23,300
Hello?

687
00:45:29,860 --> 00:45:33,420
You can hear, it's very clear.

688
00:45:35,420 --> 00:45:38,900
Jian-Wei's team has created
a network of optical fibres

689
00:45:38,900 --> 00:45:43,340
more than 1,000 miles long,
that can carry secure information

690
00:45:43,340 --> 00:45:44,900
from Beijing to Shanghai.

691
00:45:46,740 --> 00:45:49,300
It's used by banks
and data companies.

692
00:45:51,300 --> 00:45:55,740
Here is all the city which are
connect to the network.

693
00:45:55,740 --> 00:45:58,540
So here is Shanghai,
here is China Bank,

694
00:45:58,540 --> 00:46:00,860
and the here is our control centre.

695
00:46:00,860 --> 00:46:04,700
So people are really using
that secure information transfer.

696
00:46:04,700 --> 00:46:09,660
But there is a limit to how far
quantum signals can be sent

697
00:46:09,660 --> 00:46:12,140
through optical fibres.

698
00:46:12,140 --> 00:46:14,140
To send signals further,

699
00:46:14,140 --> 00:46:17,900
Jian-Wei's team launched
the world's first

700
00:46:17,900 --> 00:46:20,060
quantum communications satellite.

701
00:46:22,660 --> 00:46:26,260
Above Earth's atmosphere,
there are fewer obstacles,

702
00:46:26,260 --> 00:46:29,500
and quantum particles
can travel much further.

703
00:46:35,420 --> 00:46:39,180
Each night, teams on the ground
prepare to track the satellite

704
00:46:39,180 --> 00:46:40,940
across the sky.

705
00:46:44,020 --> 00:46:47,900
Laser guidance equipment locks
onto the satellite to allow signals

706
00:46:47,900 --> 00:46:50,100
to be sent and received.

707
00:46:52,420 --> 00:46:56,020
The team aims to use this equipment
to create a new secure

708
00:46:56,020 --> 00:46:59,500
communications system using
quantum entanglement.

709
00:47:01,740 --> 00:47:05,580
The satellite will send
entangled photons to two users.

710
00:47:07,260 --> 00:47:10,620
An eavesdropper could intercept
one of the entangled photons,

711
00:47:10,620 --> 00:47:14,860
measure it and send on
a replacement photon.

712
00:47:14,860 --> 00:47:17,420
But it wouldn't be
an entangled photon.

713
00:47:17,420 --> 00:47:20,220
Its properties wouldn't match.

714
00:47:20,220 --> 00:47:23,980
And it would be clear
an eavesdropper was on the line.

715
00:47:23,980 --> 00:47:27,540
In theory, this technique
could be used to create a totally

716
00:47:27,540 --> 00:47:30,620
secure global communication network.

717
00:47:31,980 --> 00:47:35,940
So the next step is we will
have ground station, for example

718
00:47:35,940 --> 00:47:39,780
in Canada, and also in Africa,
and in many country,

719
00:47:39,780 --> 00:47:41,620
so we will use our satellite

720
00:47:41,620 --> 00:47:44,500
for the global quantum
communication.

721
00:47:44,500 --> 00:47:48,100
We want to push this technology
as far as possible.

722
00:47:48,100 --> 00:47:52,700
These are the first steps
of a completely unhackable

723
00:47:52,700 --> 00:47:55,460
quantum internet of the future,

724
00:47:55,460 --> 00:47:58,460
made possible by
quantum entanglement.

725
00:48:00,300 --> 00:48:02,220
But there's a problem.

726
00:48:02,220 --> 00:48:03,980
What if the loophole

727
00:48:03,980 --> 00:48:07,740
in our experimental proof
of entanglement exists,

728
00:48:07,740 --> 00:48:11,820
and spooky action at a distance
isn't real after all?

729
00:48:13,020 --> 00:48:16,620
It could mean entangled
photons are not the path

730
00:48:16,620 --> 00:48:18,740
to complete security.

731
00:48:20,300 --> 00:48:24,020
So by using light released
from quasars, the team

732
00:48:24,020 --> 00:48:28,020
in the Canary Islands is hoping
to close this loophole and prove

733
00:48:28,020 --> 00:48:31,700
that entanglement is as spooky
as Bohr always claimed.

734
00:48:33,660 --> 00:48:36,180
Dominik and Jason
are at one telescope.

735
00:48:38,100 --> 00:48:40,020
Anton is at the other.

736
00:48:51,540 --> 00:48:52,740
OK, ciao.

737
00:48:59,420 --> 00:49:04,420
With clear skies finally overhead,
the huge telescopes awaken.

738
00:49:10,740 --> 00:49:14,420
Poised to collect light
from distant galaxies.

739
00:49:18,660 --> 00:49:19,740
Moving.

740
00:49:23,020 --> 00:49:24,260
Dark count level.

741
00:49:25,860 --> 00:49:28,620
We're doing everything, we're doing
everything at once now.

742
00:49:28,620 --> 00:49:32,460
The guys are setting the state

743
00:49:32,460 --> 00:49:33,900
of the entangled photon pair.

744
00:49:33,900 --> 00:49:36,540
We'll try to acquire the quasar.

745
00:49:36,540 --> 00:49:40,540
We're just centring it and making
the feeder view as small as possible

746
00:49:40,540 --> 00:49:43,060
to be sure that we only have
the quasar.

747
00:49:43,060 --> 00:49:45,460
OK. It's guiding now. Yes.

748
00:49:45,460 --> 00:49:47,860
One more image. OK.

749
00:49:49,100 --> 00:49:51,300
All right. Good, good, good. Yes.

750
00:49:51,300 --> 00:49:52,860
OK. Yeah, that's good.

751
00:49:53,940 --> 00:49:58,060
Looks like... Let's say 91,
to be conservative, of purity.

752
00:49:59,660 --> 00:50:03,860
With the telescopes now locked
onto two different quasars,

753
00:50:03,860 --> 00:50:06,980
the team begins to take readings
from their equipment.

754
00:50:20,100 --> 00:50:23,460
We did the full...
the full cosmic Bell Test.

755
00:50:23,460 --> 00:50:24,660
What?

756
00:50:24,660 --> 00:50:26,460
Yeah, we're doing
the full cosmic Bell Test.

757
00:50:27,860 --> 00:50:33,260
It's working. Light from quasars
is selecting which filters are used

758
00:50:33,260 --> 00:50:35,260
to measure the entangled photons.

759
00:50:37,700 --> 00:50:40,540
It is exciting. It is...

760
00:50:40,540 --> 00:50:45,820
Now we do have a test, but it's not
clear what the outcome will be.

761
00:50:54,660 --> 00:50:57,460
Everything's exactly the same.
Beautiful, perfect.

762
00:51:15,820 --> 00:51:18,820
Two months later, back in Vienna,

763
00:51:18,820 --> 00:51:21,900
the team analyses
the experimental data.

764
00:51:21,900 --> 00:51:24,580
This might take a second.

765
00:51:27,020 --> 00:51:29,620
The numbers look really great,

766
00:51:29,620 --> 00:51:33,740
and it is extremely pleasing to see
that all this works out nice.

767
00:51:33,740 --> 00:51:37,780
We clearly see correlations that
correspond to quantum mechanics.

768
00:51:37,780 --> 00:51:41,220
The results show entanglement.

769
00:51:43,620 --> 00:51:47,220
The data shows that the pairs
of photons correlated

770
00:51:47,220 --> 00:51:49,940
more than Einstein's physics
predicts.

771
00:51:51,220 --> 00:51:54,460
And since the light from the quasars
controlling the test

772
00:51:54,460 --> 00:51:57,100
was nearly eight billion years old,

773
00:51:57,100 --> 00:51:59,740
it's extremely unlikely
that anything

774
00:51:59,740 --> 00:52:03,020
could have affected
its random nature.

775
00:52:03,020 --> 00:52:06,100
This remaining loophole
seems to be closed.

776
00:52:06,100 --> 00:52:09,060
It seems Einstein was wrong.

777
00:52:10,380 --> 00:52:13,460
The experiment we did
is just fantastic.

778
00:52:13,460 --> 00:52:16,620
The big cosmos comes down

779
00:52:16,620 --> 00:52:19,300
to control a small
quantum experiment.

780
00:52:19,300 --> 00:52:22,700
That in itself is beautiful.

781
00:52:26,340 --> 00:52:32,660
I think to do these experiments
is a question of honesty.

782
00:52:32,660 --> 00:52:35,820
You have to do them -
as long as there are loopholes,

783
00:52:35,820 --> 00:52:38,580
you have to close them,
as much as possible.

784
00:52:38,580 --> 00:52:40,700
This, I consider an obligation.

785
00:52:44,740 --> 00:52:47,420
You know, honestly, I still...
I still get chills.

786
00:52:47,420 --> 00:52:50,980
I mean, when I realise
what our team was able to do

787
00:52:50,980 --> 00:52:54,540
in this intellectual journey
that stretches back to the early

788
00:52:54,540 --> 00:52:56,460
years of the 20th century.

789
00:52:56,460 --> 00:53:00,860
There's hardly any room left
for a kind of alternative,

790
00:53:00,860 --> 00:53:04,300
Einstein-like explanation.

791
00:53:04,300 --> 00:53:05,820
We haven't ruled it out,

792
00:53:05,820 --> 00:53:09,100
but we've shoved it into such
a tiny corner of the cosmos,

793
00:53:09,100 --> 00:53:12,460
as to make it even more implausible
for anything

794
00:53:12,460 --> 00:53:15,660
other than entanglement
to explain our results.

795
00:53:17,540 --> 00:53:21,900
Accepting that entanglement is part
of the natural world around us

796
00:53:21,900 --> 00:53:23,980
has profound implications.

797
00:53:25,740 --> 00:53:29,740
It means you must accept
that an action in one place

798
00:53:29,740 --> 00:53:33,380
can have an instant effect anywhere
in the universe, as if there's no

799
00:53:33,380 --> 00:53:35,380
space between them.

800
00:53:37,460 --> 00:53:40,620
Or that particles only
take on physical properties

801
00:53:40,620 --> 00:53:42,500
when we observe them.

802
00:53:45,180 --> 00:53:48,180
Or we must accept both.

803
00:53:48,180 --> 00:53:49,700
We're left with conclusions

804
00:53:49,700 --> 00:53:52,340
about the universe that make
no sense whatsoever.

805
00:53:53,420 --> 00:53:58,100
Science is stepping outside of all
of our boundaries of common sense,

806
00:53:58,100 --> 00:54:01,380
and yet finding ways
to explain the universe.

807
00:54:02,500 --> 00:54:04,860
It is almost like being
in Alice in Wonderland,

808
00:54:04,860 --> 00:54:06,660
where everything is possible.

809
00:54:13,660 --> 00:54:17,220
It was first seen as an unwelcome
but unavoidable consequence

810
00:54:17,220 --> 00:54:19,300
of quantum mechanics.

811
00:54:20,780 --> 00:54:24,900
Now, after a century of disputes
and discoveries,

812
00:54:24,900 --> 00:54:27,460
spooky action at a distance

813
00:54:27,460 --> 00:54:29,580
is finally at the heart of
modern physics.

814
00:54:31,740 --> 00:54:36,540
At the Institute for Advanced Study,
where the concept of entanglement

815
00:54:36,540 --> 00:54:42,780
was first discovered, researchers
are using it in powerful new ideas

816
00:54:42,780 --> 00:54:46,900
that could lead to a single unified
theory of the universe.

817
00:54:46,900 --> 00:54:48,940
The Holy Grail of physics.

818
00:54:51,260 --> 00:54:55,220
Einstein's theories of special
and general relativity perfectly

819
00:54:55,220 --> 00:54:58,900
describe space, time and gravity

820
00:54:58,900 --> 00:55:02,140
at the largest scales
of the universe,

821
00:55:02,140 --> 00:55:07,300
while quantum mechanics perfectly
describes the tiniest scales.

822
00:55:07,300 --> 00:55:10,820
Yet these two theories have never
been brought together.

823
00:55:13,180 --> 00:55:17,860
So far, we've not yet had a single
complete theory that is both quantum

824
00:55:17,860 --> 00:55:20,860
mechanical, and reproduces
the prediction of Einstein's

825
00:55:20,860 --> 00:55:24,500
wonderful theory of
general relativity.

826
00:55:24,500 --> 00:55:27,500
Maybe the secret is entanglement.

827
00:55:27,500 --> 00:55:29,580
What we are learning these days

828
00:55:29,580 --> 00:55:31,700
is that in some sense,
quantum theory

829
00:55:31,700 --> 00:55:33,580
is really the dominant force,

830
00:55:33,580 --> 00:55:36,060
and that we might have to give up

831
00:55:36,060 --> 00:55:38,860
what Einstein holds sacred,

832
00:55:38,860 --> 00:55:40,180
namely space and time.

833
00:55:40,180 --> 00:55:43,340
So he was always thinking, "Well,
we have little pieces of space

834
00:55:43,340 --> 00:55:47,140
"and time, and out of this,
we build the whole universe."

835
00:55:47,140 --> 00:55:53,300
In a radical theory,
known as the holographic universe,

836
00:55:53,300 --> 00:55:57,220
space and time are created
by entangled quantum particles

837
00:55:57,220 --> 00:56:01,180
on a sphere that is
infinitely far away.

838
00:56:02,540 --> 00:56:07,580
What's happening in space in some
sense, all described in terms

839
00:56:07,580 --> 00:56:09,820
of a screen outside here.

840
00:56:09,820 --> 00:56:13,940
The ultimate description
of reality resides on this screen.

841
00:56:13,940 --> 00:56:18,020
Think of it as kind of
quantum bits living on that screen,

842
00:56:18,020 --> 00:56:23,060
and this, like a movie projector,
creates an illusion

843
00:56:23,060 --> 00:56:27,020
of the three-dimensional reality
that I'm now experiencing.

844
00:56:28,620 --> 00:56:32,580
This wild idea may sound
far-fetched, but it reveals

845
00:56:32,580 --> 00:56:37,860
that mathematically, the space
and time we experience every day

846
00:56:37,860 --> 00:56:40,700
could be created by
the quantum world.

847
00:56:42,100 --> 00:56:46,900
Entanglement could be what forms
the true fabric of the universe.

848
00:56:49,620 --> 00:56:53,540
The most puzzling element
of entanglement, that, you know,

849
00:56:53,540 --> 00:56:56,460
somehow two points in space
can communicate,

850
00:56:56,460 --> 00:57:00,780
becomes less of a problem, because
space itself has disappeared.

851
00:57:00,780 --> 00:57:04,340
In the end, we just have
this quantum mechanical world.

852
00:57:04,340 --> 00:57:06,340
There is no space any more.

853
00:57:06,340 --> 00:57:10,940
And so in some sense, the paradoxes
of entanglement,

854
00:57:10,940 --> 00:57:13,940
the EPR paradox,
disappears into thin air.

855
00:57:19,660 --> 00:57:22,900
Truly understanding
quantum mechanics will only happen

856
00:57:22,900 --> 00:57:25,820
when we put ourselves
on the entanglement side.

857
00:57:25,820 --> 00:57:30,020
When we stop privileging the world
that we see, and start

858
00:57:30,020 --> 00:57:32,300
thinking about the world
as it actually is.

859
00:57:35,180 --> 00:57:39,580
Science has made enormous progress
for centuries by sort of breaking

860
00:57:39,580 --> 00:57:42,180
complicated systems down into parts.

861
00:57:42,180 --> 00:57:43,420
When we come to phenomena

862
00:57:43,420 --> 00:57:45,660
like quantum entanglement,
that scheme breaks.

863
00:57:46,900 --> 00:57:49,700
When it comes to the bedrock
of quantum mechanics,

864
00:57:49,700 --> 00:57:53,580
the whole is more than the sum
of its parts.

865
00:57:55,740 --> 00:58:00,980
The basic motivation is just
to learn how nature works,

866
00:58:00,980 --> 00:58:03,340
what's really going on.

867
00:58:03,340 --> 00:58:05,260
Einstein said it very nicely.

868
00:58:05,260 --> 00:58:08,700
He's not interested in this detailed
question or that detailed question.

869
00:58:08,700 --> 00:58:11,300
He just wanted to know,

870
00:58:11,300 --> 00:58:14,900
"What were God's thoughts
when he created the world?"