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Lying just beneatheveryday reality

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is a breathtaking world,

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where much of what we perceive
about the universe is wrong.

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Physicist and best-selling
author Brian Greene takes you

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on a journey that bends the rules of human experience.

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BRIAN GBEENE: Why don't we ever see events unfold in reverse order?

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According to the laws of physics, this can happen.

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It's a world that comes to light

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as we probe the most extreme realms of fhe cosmos,

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from black holes to the Big Bang

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to the very heart of matter itself.

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I'm going to have what he's having.

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Here, our universe may be one of numerous parallel realities

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The three-dimensional world may be just an illusion,

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and there's no distinction

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between past, present and future.

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GREENE: But how could this be?

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How could we be so wrong about something so familiar?

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Does it bother us?

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Absolutely.

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There's no principle built into the laws ot nature

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that say that theoretical physicists have to be happy.

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It's a game-changing perspective

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that opens up a new world of posibilities.

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Coming up...

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The realm of tiny atoms and particles: the quantum realm.

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The laws here seem impossible.

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There's a sense in which things don't like to be tied down

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to just one location.

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Yet they're vital to everything in the universe.

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There's no disagreement between quantum mechanics

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and any experiment that's ever been done.

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What do they reveal about the nature of reality?

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"Take a"Quantum Leap"on "The Fabric of the Cosmos,"

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right now on NOVA.

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Major funding for NOVA is provided by the following:

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And...

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And by the Corporation for Public Broadcasting

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and by contributions to your PBS station form ;

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Major funding for "The Fabric of the Cosmos"

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is provided by the National Science Foundation.

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And...

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Supporting original research and public understanding

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of science, technology, engineering and mathematics.

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Additional funding is provided by...

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And the George D. Smith Fund.

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GREENE: For thousands of years,

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we've been tryind to unlock

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the mysteries of how the universe works.

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And we've done pretty well, coming up with a set of laws

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that describes the clear and certain motion

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of galaxies and stars and planets.

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But now we know, at a fundamental level

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things are a lot were fuzzy,

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because we've discovered a revolutionary new set of laws

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that have completely transformed our picture of the universe.

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From outer space, to the heart of New York city

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to the microscopic realm,

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our view of the world has shifted,

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thanks to these strange and mysterious laws

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that are redefining our understanding of reality.

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Thay are the laws of quantum mechanics.

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Quantum mechanics rules over every atom and tiny particle

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in every piece of matter.

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In stars and planets,

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in rocks and buildings,

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and in you and me.

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We don't notice the strangeness of quantum mechanics

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in everyday life,

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but it's always there, if you know where to look.

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You just have to change your perspective

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and get down to the tiniest of scales,

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to the level of atoms and the particles inside them.

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down at the quantum level the laws that govern this tiny realm

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appear completely different from the familiar laws

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that govern big, everyday objects.

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And once you catch a glimpse of them,

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you never look at the world in quite the same way.

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It's almost impossible to picture how weird things can get

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down at the smallest of scales.

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But what if you could visit a place like this,

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where the quantum laws were obvious,

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where people and objects behave like tiny atoms and particles?

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You'd be in for quite a show.

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Here, objects do things that seem crazy.

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I mean, in the quantum world,

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there's a sense in which things don't like to be tied down

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to just one location,

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or to follow just one path.

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It's almost as if things were in more then one place at a time.

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And what I do here can have an immediate effect somewhere else,

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even if there's no one there.

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And here's one of the strangest things of all

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if people behaved like the particles inside the atom,

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then most of the time,

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you wouldn;t knom exactly where they were.

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Instead, they could be almost anywhere,

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until you look for them.

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Hey.

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I'm going to have what he's having.

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So why do we believe these bizarre laws?

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Well, for over 75 years,

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we've been using them to make predictions

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for how atoms and particles should behave.

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And in experiment after experiment,

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the quantum laws have always been right.

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It's the best theory we have.

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There are literally billions of pieces

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of confirming evidence for quantum mechanics.

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It has passed so many tests of so many bizarre predictions.

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There's no disagreement between quantum mechanics

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and any enperiment that's ever been done.

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The quantum laws become most obvious

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when you get down to tiny scales, like atoms,

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but consider this,

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Im made of atoms.

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So are you.

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So is everything else we see in the world around us.

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So it must be the case that these weird quantum laws

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are not just telling us about small things.

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They're telling us about reality.

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So how did we discover them,

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these strange laws that seem to contradict

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much of what we thought we knew about the universe

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Not long ago, we thought we had it pretty much figured out.

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The rules that govern how planets orbit the sun.

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How a ball arcs through the sky.

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How ripples move across the surface of a pond.

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These laws were all spelled out in a series of equations

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called classical mechanics,

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and they allowed us to predict

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the behavior of things with certainty.

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It all seemed to be making perfect sense

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until about a hundred years ago,

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when scientists were struggling to explain

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some unusual properties of light.

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In particular, the kind of light that glowed from gases

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when they were heated in a glass tube.

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When scientists observed this light through a prism,

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they saw something they'd never expected.

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PETER GALISON:If you heated up some gas and looked at it through a prism,

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it formed lines.

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Not the continuous spectrum that you see projected

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by a piece of cut glass on your table,

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but very distinct lines.

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DAVID KAISER: It wouldn't give out a smear,

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kind of complete rainbow of light.

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It would give out sort of pencil beams of light

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at very specific colors.

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GALISON:And it was something of a mystery,

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how to understand what was going on.

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GREENE: An explanation for the mysterious lines of color

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would come from a band of radical scientists

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who, at the begining of the 20th century,

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were grappling with the fundamental nature

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of the physical world.

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And some of the most startling insights

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come from the mind of Niels Bohr,

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a physicist who loved to discuss new ideas over ping-pong.

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Bohr was convinced that the solution to the mystery

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lay at the heart of matter,in the structure of the atom.

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He thought that atoms resemble tiny solar systems,

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with even tinier particles called electrons

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orbiting around a nucleus,

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much the way the planets orbit around the sun.

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But unlike the solar system,Bohr proposed that electrons

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could not move in just any orbit.

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Instead, only certain orbits were allowed.

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GALISON:And he had a really surprising

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and completely counterphysical idea,

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which was that there were definite states,

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fixed orbits that these electrons could have,

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and only those orbits.

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GREENE:Bohr said that when an atow was heated,

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its electrons would become agitated

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and leap from one fixed orbit to another.

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Each downward leap would emit energy in the form of light

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in very specific wavelengths,

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and thats why atoms produce very specific colors.

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This is where we get the phrase "quantum leap".

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JIM GATES: If it weren't for the quantum leap,

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you would have this smear of color coming out from an atom

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as it got excited or de-excited.

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But that's not what we see in the laborayory.

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You see very sharp reds and very sharp greens.

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It's the quantum leap

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that's the orign and the author of that sharp color.

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GREENE:What made the quantum leap so surprising

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was that the electron goes direcity from here to there,

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seemingly without moving through the space in between.

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It was as if Mars suddenly popped from its own orbit

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out to Jupiter.

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Bohr argued that the quantum leap arises from a fundamental

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and fundamentally weird,property of electrons in atoms,

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that their energy comes in discrete chunks

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that can't be subdivided,

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specific minmum quantities called "quanta".

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And that's why there are only discrete, specific orbits

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that electrons can occupy.

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KAISER:An electron had to be
here or there,

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and simply nowhere in between.

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And that's like nothing we experience in everyday life.

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Think of your daily life.

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When you eat food, you think your food is quantized?

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Do you think that you have to take

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a certain amount of minimum food?

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Food is not quantized.

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But the energy of eleotrons in an atom are quantized.

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That is very mysterious,why that is.

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GREENE:As mysterious as it might be

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far tiny particles in an atom to act this way,

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the evidence quickly mounted,showing that Bohr was right.

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In more and more experiments,

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electrons follewed a different set of rules

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than planets or png-pong balls.

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Bohr's discovery was a game-changer.

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And with this new picture of the atom, Bohr and his colleagues

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found themselves on a collision course

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with the accepted laws of physics.

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The quantum leap was just the begining.

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Soon, Bohr's radical views would bring him head-to-head

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with one of the greatest physicist in history

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Albert Einstein was not afraid of new ideas.

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But during the 1920s,the world of quantum mechanics

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began to veer in a direction
Einstein did not want to go,

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a direction that sharp diverged

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from the absolute,definitive predictions

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that were the hallmark of classcal physics.

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TEGMARK:If you asked Einstein or other physicists at the time

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what it was that distinguished physics

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from all kind of flaky speculation,

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they would have said,

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"It's that we can predict things with certainty."

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And quantum mechanics

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seemed to pull the rug out from under that.

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GREENE:One test in particular,

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which would come to be known as the double-slit experiment,

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exposed quantum mysteries like no other.

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If you were looking for a description of reality

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based on certainty, your expectations would  be shattered.

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We can get a pretty good feel for the double-slit experiment,

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and how dramatically it alters our picture of reality,

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by carrying out
a similar  xperiment,

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not on the scale of tiny particles

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but on the scale of more ordinary objects,

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like those you'd find here in a bowling alley.

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But first I need to make

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a couple of adjustments to the lane.

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You'd expect that if I roll

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a few of these balls down the lane,

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they'll either be stopped by the barrier

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or pass through one or the other slit

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and hit the screen at the back.

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And in fact,that's just what happens.

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Those balls that make it through always hit the screen

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directly behind either the left slit or the right slit.

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The double slit experiment was much like this,

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except instead of bowling balls,

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you use electrons, which are billions of times smaller.

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you can picture them like this.

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Let'see what happens if I throw a bunch of these balls.

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When electrons are hurled at the two slits,

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00:15:55,371 --> 00:15:57,362
something very different happens on the other side.

264
00:15:57,457 --> 00:16:00,699
Instead of hitting just two areas,

265
00:16:00,835 --> 00:16:03,497
the electrons land all over the detector screen,

266
00:16:03,588 --> 00:16:06,170
creating a pattern of stripes,

267
00:16:06,257 --> 00:16:09,420
including some right between the two slits,

268
00:16:09,552 --> 00:16:13,170
the very place you'd think would be blocked.

269
00:16:13,264 --> 00:16:17,633
So what's going on?

270
00:16:17,727 --> 00:16:20,389
Well, to physicists,even in the 1920s,

271
00:16:20,480 --> 00:16:23,597
this pattern could mean only one thing:

272
00:16:23,733 --> 00:16:27,567
waves.

273
00:16:27,653 --> 00:16:29,518
Waves do all kinds of interesting things,

274
00:16:29,614 --> 00:16:33,402
thigs that bowling balls would never do.

275
00:16:33,493 --> 00:16:35,279
They can split.

276
00:16:35,411 --> 00:16:37,743
They can combine.

277
00:16:37,872 --> 00:16:40,579
If I sent a wave at water through the double slits,

278
00:16:40,708 --> 00:16:42,664
it would split in two,

279
00:16:42,752 --> 00:16:45,869
and then the two sets of waves would intersect.

280
00:16:45,963 --> 00:16:48,079
Their peaks and valleys would combine,

281
00:16:48,174 --> 00:16:51,712
getting bigger in some places,smaller in others,

282
00:16:51,802 --> 00:16:56,512
and sometimes they'd cancel each other out.

283
00:16:56,599 --> 00:16:58,135
With the height of the water

284
00:16:58,267 --> 00:17:00,508
corresponding to brightness on the screen,

285
00:17:00,603 --> 00:17:04,312
the peaks and valleys would create a series of stripes

286
00:17:04,440 --> 00:17:08,479
in what'known as an interference pattern.

287
00:17:08,611 --> 00:17:12,354
So how could electrons,which are particles,

288
00:17:12,448 --> 00:17:14,689
form that pattern?

289
00:17:14,784 --> 00:17:20,074
How could a single electron end up in places a wave would go?

290
00:17:20,164 --> 00:17:21,370
Particles are particles.

291
00:17:21,457 --> 00:17:22,788
Waves are waves.

292
00:17:22,875 --> 00:17:25,241
How can a particle be a wave?

293
00:17:25,336 --> 00:17:27,418
Unless you give up the idea that it's a particle.

294
00:17:27,505 --> 00:17:29,245
And think, "Aha!"

295
00:17:29,340 --> 00:17:33,299
This thing that I thought was a particle was actually a wave.

296
00:17:33,386 --> 00:17:35,593
A wave in an ocean,that's not a particle.

297
00:17:35,680 --> 00:17:39,298
The ocean is made out of particles,

298
00:17:39,433 --> 00:17:41,845
but the waves in the ocean are not particles.

299
00:17:41,978 --> 00:17:47,018
And rocks are not waves,rocks are rocks.

300
00:17:47,149 --> 00:17:48,810
so a rock is an example of a particle,

301
00:17:48,943 --> 00:17:53,027
an ocean wave is an example of an ocean wave,

302
00:17:53,155 --> 00:17:56,989
and now somebody's telling you a rock is like an ocean wave.

303
00:17:57,076 --> 00:17:58,156
What?

304
00:17:58,286 --> 00:18:00,197
Back in the 1920s,

305
00:18:00,329 --> 00:18:02,490
when a version of this experiment was first done,

306
00:18:02,623 --> 00:18:06,241
scientists struggled to understand this wavy behavior.

307
00:18:07,878 --> 00:18:11,336
Some wondered if a singe electron, while in motion,

308
00:18:11,424 --> 00:18:14,461
might spread out into a wave.

309
00:18:14,552 --> 00:18:17,009
And the physicist Erwin Schrodinger

310
00:18:17,138 --> 00:18:20,301
came up with an equation that seemed to descride it.

311
00:18:20,391 --> 00:18:22,973
STEVEN WEINBERG: Schrodinger thought that this wave

312
00:18:23,060 --> 00:18:26,348
was a description of an extended electron,

313
00:18:26,439 --> 00:18:28,225
that somehow an electron got smeared out

314
00:18:28,357 --> 00:18:33,852
and it was no longer a point,but was like a mush.

315
00:18:33,946 --> 00:18:35,686
There was a lot of argument

316
00:18:35,781 --> 00:18:37,692
about exactly what this represented.

317
00:18:37,783 --> 00:18:41,275
GREENE
Finally, a physicist named Max Born

318
00:18:41,370 --> 00:18:43,952
came up with a new and revolutionary idea

319
00:18:44,040 --> 00:18:47,032
for what the wave equation described.

320
00:18:47,168 --> 00:18:51,081
Born said that the wave is not a smeared-out electron

321
00:18:51,213 --> 00:18:55,001
or anything else previously encountered in science.

322
00:18:55,092 --> 00:18:57,424
Instead, he declared it's something

323
00:18:57,553 --> 00:19:02,343
that's really peculiar:a probability wave.

324
00:19:02,433 --> 00:19:07,427
That is, Born argued that the size of the wave at any location

325
00:19:07,563 --> 00:19:12,057
predicts the likelihood of the electron being found there.

326
00:19:12,151 --> 00:19:14,858
WEINBERG:Where the wave is big,

327
00:19:14,945 --> 00:19:17,061
that's net where most of the electron is,

328
00:19:17,198 --> 00:19:19,735
that's where the electron is most likely to be.

329
00:19:19,867 --> 00:19:21,732
And that's just very strange, right?

330
00:19:21,827 --> 00:19:24,990
So the electron on its own seems to be a jumble of possibilities.

331
00:19:26,832 --> 00:19:28,663
PETER FISHER:You're not allowed to ask,

332
00:19:28,751 --> 00:19:32,164
"Where is the electron right now?"

333
00:19:32,254 --> 00:19:35,746
You are allowed to ask,"If I look for the electron

334
00:19:35,883 --> 00:19:38,420
"in this little particular part of space,

335
00:19:38,511 --> 00:19:43,096
what is the likelihood I will find it there?"

336
00:19:43,182 --> 00:19:46,674
I mean, that bugs anyone anytime.

337
00:19:46,769 --> 00:19:48,976
As weird as it sounds,

338
00:19:49,105 --> 00:19:52,768
this new way of describing how particles like electrons move

339
00:19:52,858 --> 00:19:53,893
is actually right.

340
00:19:55,319 --> 00:19:57,685
When I throw a single electron,

341
00:19:57,780 --> 00:20:00,943
I can never predict where it will land,

342
00:20:01,033 --> 00:20:02,864
but if I use schrodinger's equation

343
00:20:02,952 --> 00:20:04,943
to find the electron's probability wave,

344
00:20:05,037 --> 00:20:07,244
I can predict with great certainty

345
00:20:07,331 --> 00:20:10,789
that if I throw enough electrons,

346
00:20:10,876 --> 00:20:13,162
then, say, 33.1% would end up "here,"

347
00:20:13,295 --> 00:20:17,914
7.9% would end up "there,"and so on.

348
00:20:18,008 --> 00:20:19,464
These kinds of predictions

349
00:20:19,593 --> 00:20:23,302
have been confirmed again and again by experiments.

350
00:20:23,431 --> 00:20:25,638
And so, the equations of quantum mechanics

351
00:20:25,725 --> 00:20:29,388
turn out to be amazingly accurate and precise,

352
00:20:29,478 --> 00:20:33,767
so long as you can accept that it's all about probability.

353
00:20:36,402 --> 00:20:38,188
If you think that probability means

354
00:20:38,320 --> 00:20:40,276
you're reduced to guessing,

355
00:20:40,364 --> 00:20:44,357
the casinos of Las Vegas are ready to prove you wrong.

356
00:20:49,498 --> 00:20:51,705
Try your hand at any one of these games of chance,

357
00:20:51,834 --> 00:20:53,244
and you can see the power of probability.

358
00:20:58,132 --> 00:21:00,464
Let's say I place a $20 bet on number 29

359
00:21:00,551 --> 00:21:03,042
here at the roulette table.

360
00:21:08,601 --> 00:21:10,683
The house doesn't know whether I'll win on this spin

361
00:21:10,770 --> 00:21:13,182
or the next or the next.

362
00:21:13,314 --> 00:21:14,429
One.

363
00:21:17,526 --> 00:21:20,359
But it does know the probability that I'll win.

364
00:21:20,488 --> 00:21:22,444
In this game,it's one in 38.

365
00:21:25,034 --> 00:21:25,989
21.

366
00:21:31,373 --> 00:21:32,658
(bell rings)

367
00:21:32,750 --> 00:21:33,830
WOMAN:29.

368
00:21:36,587 --> 00:21:39,203
So even though I may win now and then, in the long run,

369
00:21:39,340 --> 00:21:43,299
the house always takes in more than it loses.

370
00:21:43,385 --> 00:21:45,751
The point is, the house doesn't have to know the outcome

371
00:21:45,888 --> 00:21:48,971
at any single card game,roll of the dice,

372
00:21:49,058 --> 00:21:51,219
or spin of the roulette wheel

373
00:21:51,310 --> 00:21:53,596
Casinos can still be confident that over the course

374
00:21:53,729 --> 00:21:59,645
of thousands of spins, deals,and rolls, they will win,

375
00:21:59,735 --> 00:22:02,943
and they can predict with exquisite accuracy

376
00:22:03,072 --> 00:22:05,859
exactly how often.

377
00:22:05,950 --> 00:22:07,736
According to quantum mechanics,

378
00:22:07,827 --> 00:22:12,491
the world itself is a game of chance much like this.

379
00:22:12,581 --> 00:22:14,537
All the matter in the universe

380
00:22:14,625 --> 00:22:16,957
is made of atoms and subatomic particles

381
00:22:17,086 --> 00:22:20,920
that are ruled by probability,not certainty.

382
00:22:21,048 --> 00:22:23,835
EDWARD FARHI:At base, nature is described

383
00:22:23,926 --> 00:22:26,133
by an inherently probabilistic theory.

384
00:22:26,262 --> 00:22:28,924
And that is highly counterintuitive,

385
00:22:29,056 --> 00:22:32,799
and something which many people would find difficulty accepting.

386
00:22:32,935 --> 00:22:37,099
GREENE: One person who found it difficult was Einstein.

387
00:22:37,231 --> 00:22:40,439
Einstein could not believe that the fundamental nature

388
00:22:40,568 --> 00:22:45,187
of reality, at the deepest lever, was determined by chance.

389
00:22:45,281 --> 00:22:47,363
And this is what Einstein could not accept.

390
00:22:47,449 --> 00:22:51,909
Einstein said,"God does not throw dice."

391
00:22:51,996 --> 00:22:56,456
He didn't like the idea that we couldn't with certainty say,

392
00:22:56,584 --> 00:22:59,951
"This happens or that happens."

393
00:23:00,087 --> 00:23:01,452
GREENE: But a lot of other physicists

394
00:23:01,589 --> 00:23:03,705
weren't so put off by probability,

395
00:23:03,799 --> 00:23:07,087
because the equations at quantum mechanics

396
00:23:07,177 --> 00:23:09,463
gave them the power to predict the behavior

397
00:23:09,597 --> 00:23:12,088
of groups of atoms and tiny particles

398
00:23:12,182 --> 00:23:14,969
with astounding precision.

399
00:23:15,060 --> 00:23:17,392
Before long.that power would lead

400
00:23:17,479 --> 00:23:19,640
to some very big inventions.

401
00:23:19,773 --> 00:23:25,439
Lasers, transistors,the integrated circuit,

402
00:23:25,529 --> 00:23:29,397
the entire field of electronics.

403
00:23:29,491 --> 00:23:32,858
MAX TEGMARK:If quantum mechanics suddenly went on strike,

404
00:23:32,995 --> 00:23:35,327
every single machine that we have in the US, almost,

405
00:23:35,414 --> 00:23:38,281
would stop functioning.

406
00:23:38,375 --> 00:23:40,991
GREENE:The equations of quantum mechanics

407
00:23:41,086 --> 00:23:44,123
would help engineers design microscopic switches

408
00:23:44,214 --> 00:23:47,377
that direct the flow of tiny electrons

409
00:23:47,509 --> 00:23:51,377
and control virtually every one of today's computers,

410
00:23:51,513 --> 00:23:54,846
digital cameras,and telephones.

411
00:23:54,934 --> 00:23:57,846
ADAMS: All the devices that we live on,diodes, transistors, just...

412
00:23:57,978 --> 00:24:00,811
that form the basis of information technology,

413
00:24:00,898 --> 00:24:02,183
the basis of daily life in all sorts of ways, they work.

414
00:24:02,316 --> 00:24:03,681
And why do they work?

415
00:24:03,776 --> 00:24:05,357
They work because of quantum mechanics.

416
00:24:05,486 --> 00:24:08,444
WEINBERG:l'm tempted to say that without quantum mechanics,

417
00:24:08,530 --> 00:24:12,694
we'd be back in the dark ages,but I guess more accurately,

418
00:24:12,826 --> 00:24:16,318
without quantum mechanics we'd be back in the 19th century.

419
00:24:16,413 --> 00:24:21,248
Steam engines,telegraph signals.

420
00:24:21,377 --> 00:24:24,619
TEGMARK: Quantum mechanics is the most successful theory

421
00:24:24,713 --> 00:24:27,250
that we physicists have ever discovered.

422
00:24:27,383 --> 00:24:29,965
And yet, we're still arguing

423
00:24:30,052 --> 00:24:32,043
about what it means,

424
00:24:32,179 --> 00:24:35,763
what it tells us about the nature at reality.

425
00:24:37,893 --> 00:24:39,554
GREENE:In spite of all of its triumphs,

426
00:24:39,687 --> 00:24:42,895
quantum mechanics remains deeply mysterious.

427
00:24:43,023 --> 00:24:46,936
It makes all this stuff run,but we still haven't answered

428
00:24:47,069 --> 00:24:49,731
basic questions raised by Albert Einstein

429
00:24:49,863 --> 00:24:52,900
at the way back in the 1920s and '30s,

430
00:24:53,033 --> 00:24:56,321
questions involving probability and measurement,

431
00:24:56,412 --> 00:24:58,277
the act of observation.

432
00:24:59,915 --> 00:25:04,750
For Niels Bohr, measurement changes everything.

433
00:25:04,837 --> 00:25:08,671
He believed that before you measured or observed a particle,

434
00:25:08,757 --> 00:25:11,544
its characteristics were uncertain.

435
00:25:11,635 --> 00:25:15,594
For example, an electron in the double-slit experiment.

436
00:25:15,723 --> 00:25:18,965
Before the detector at the back pinpoints its location,

437
00:25:19,101 --> 00:25:21,387
it could be almost anywhere,

438
00:25:21,478 --> 00:25:24,185
with a whole range of possibilities.

439
00:25:24,273 --> 00:25:29,108
Until the moment you observe it,and only at that point,

440
00:25:29,194 --> 00:25:31,936
will the location's uncertainty disappear.

441
00:25:34,491 --> 00:25:36,948
According to Bohr's approach to quantum mechanics,

442
00:25:37,036 --> 00:25:39,118
when you measure a particle,

443
00:25:39,246 --> 00:25:42,363
the act at measurement forces the particle to relinquish

444
00:25:42,458 --> 00:25:45,495
all of the possible places it could have been

445
00:25:45,627 --> 00:25:49,461
and select one definite location where yon find it.

446
00:25:49,590 --> 00:25:52,457
The act of measurement is what forces the particle

447
00:25:52,593 --> 00:25:54,299
to make that choice.

448
00:25:54,428 --> 00:25:58,387
Niels Bohr accepted that the nature of reality

449
00:25:58,474 --> 00:26:00,556
was inherently fuzzy.

450
00:26:00,642 --> 00:26:02,724
But not Einstein.

451
00:26:02,811 --> 00:26:04,347
He believed in certainty,

452
00:26:04,480 --> 00:26:07,096
not just when something is measured or looked at,

453
00:26:07,191 --> 00:26:10,604
but all the time.

454
00:26:10,694 --> 00:26:14,482
As Einstein said, "I like to think the moon is there

455
00:26:14,615 --> 00:26:16,981
even when I'm not lookng at it."

456
00:26:18,702 --> 00:26:21,284
That's what Einstein was so upset about.

457
00:26:21,371 --> 00:26:23,327
Do we really think the reality of the universe rests on

458
00:26:23,457 --> 00:26:25,038
whether or not we happen to open our eyes?

459
00:26:25,167 --> 00:26:26,498
That's just bizarre.

460
00:26:26,585 --> 00:26:31,249
GREENE:Einstein was convinced something was missing from quantum theory,

461
00:26:31,340 --> 00:26:33,080
something that would describe

462
00:26:33,175 --> 00:26:37,009
all the detailed features of particles, like their locations,

463
00:26:37,096 --> 00:26:40,384
even when you were not looking at them.

464
00:26:40,516 --> 00:26:43,007
But at the time, few physicists shared his concern.

465
00:26:43,143 --> 00:26:45,008
KAISER:And Einstein just thought it was giving up

466
00:26:45,145 --> 00:26:47,602
on the job of the physicist.

467
00:26:47,689 --> 00:26:50,772
It wasn't bad physics per se,it just was totally incomplete.

468
00:26:50,859 --> 00:26:52,315
That's Einstein's refrain.

469
00:26:52,402 --> 00:26:56,065
Quantum mechanics is not incorrect,it's as for as...

470
00:26:56,198 --> 00:26:57,859
in so far as it goes,but it's incomplete.

471
00:26:57,950 --> 00:26:59,690
It doesn't capture all of the things

472
00:26:59,785 --> 00:27:02,527
that cau be said or predicted with certainty.

473
00:27:02,663 --> 00:27:07,623
GBEENE:Despite Einstein's arguments,Niels Bohr remained unmoved.

474
00:27:07,709 --> 00:27:12,328
When Einstein repeated that "God does not play dice,"

475
00:27:12,422 --> 00:27:16,461
Bohr responded,"Stop telling God what to do."

476
00:27:20,430 --> 00:27:22,591
But in 1935, Einstein thought he'd finally found

477
00:27:22,724 --> 00:27:25,090
the Achilles' Heel of quantum mechanics.

478
00:27:27,437 --> 00:27:29,598
Something so strange,

479
00:27:29,731 --> 00:27:32,222
so counter to all logical views of the universe,

480
00:27:32,317 --> 00:27:34,729
he thought it held the key

481
00:27:34,862 --> 00:27:38,150
to proving the theory was incomplete.

482
00:27:38,240 --> 00:27:42,108
It's called "entanglement."

483
00:27:42,244 --> 00:27:43,950
LEWIN: The most bizarre,

484
00:27:44,079 --> 00:27:50,666
the most absurd, the most crazy,the most ridiculous prediction

485
00:27:50,752 --> 00:27:54,916
that quantum mechanics makes is entanglement.

486
00:27:55,007 --> 00:27:59,421
GREENE:Entanglement is a theoretical prediction

487
00:27:59,511 --> 00:28:03,254
that comes from the equations of quantum mechanics.

488
00:28:03,390 --> 00:28:05,847
Two particles can become entangled

489
00:28:05,934 --> 00:28:10,223
if they're close together and their properties become in linked.

490
00:28:10,314 --> 00:28:12,145
Remarkably,quantum mechanics says

491
00:28:12,274 --> 00:28:14,105
that even if you separated those particles,

492
00:28:14,193 --> 00:28:15,933
sending them in opposite directions,

493
00:28:16,028 --> 00:28:21,068
they could remain entangled,inextricably connected.

494
00:28:21,158 --> 00:28:24,491
To understand how profoundly weird this is,

495
00:28:24,620 --> 00:28:28,283
consider a property of electrons called "spin."

496
00:28:30,500 --> 00:28:33,333
Unlike a spinning top,an electron's spin,

497
00:28:33,462 --> 00:28:35,453
as with other quantum qualities,

498
00:28:35,547 --> 00:28:38,960
is generlly completely fuzzy and uncertain

499
00:28:39,051 --> 00:28:42,384
untill the moment you measure it.

500
00:28:42,471 --> 00:28:44,257
And when you do, you'll find

501
00:28:44,348 --> 00:28:49,433
it's either spinning clockwise or counterclockwise.

502
00:28:49,519 --> 00:28:51,976
It's kind of like this wheel.

503
00:28:52,105 --> 00:28:53,811
When it stops turning,

504
00:28:53,899 --> 00:28:56,515
it will randomly land on either red or blue.

505
00:29:01,573 --> 00:29:04,155
Now imagine a second wheel.

506
00:29:04,284 --> 00:29:09,119
If these two wheels behaved like two entangled electrons,

507
00:29:09,206 --> 00:29:12,744
then every time one landed red,

508
00:29:12,834 --> 00:29:16,918
the other is guaranteed to land on blue.

509
00:29:17,005 --> 00:29:19,371
And vice-versa.

510
00:29:19,508 --> 00:29:21,874
Now, since the wheels are not connected,

511
00:29:22,010 --> 00:29:24,467
that's suspicious enough.

512
00:29:24,554 --> 00:29:26,044
But the quantum mechanics embraced by Nieh Bohr

513
00:29:26,181 --> 00:29:28,513
and his colleagues went even further,

514
00:29:28,600 --> 00:29:33,219
predicting that if one of the pair were far away,

515
00:29:33,355 --> 00:29:38,520
even on the moon, with no wires or transmitters connecting them,

516
00:29:38,652 --> 00:29:41,940
still, if you look at one and find red,

517
00:29:42,030 --> 00:29:45,648
the other is sure to be blue.

518
00:29:45,742 --> 00:29:49,735
ln other words, if you measured a particle here,

519
00:29:49,871 --> 00:29:51,827
not only would you affect it,

520
00:29:51,915 --> 00:29:55,078
but your measurement would also affect its entangled partner,

521
00:29:55,210 --> 00:29:57,792
no matter how distant.

522
00:29:57,879 --> 00:30:01,292
For Einstein, that kind of weird long-range connection

523
00:30:01,383 --> 00:30:05,217
between spinning wheels or particles was so ludicrous,

524
00:30:05,304 --> 00:30:10,219
he called it spooky:"spooky action at a distance."

525
00:30:10,350 --> 00:30:13,808
What's surprising is that when you make a measurement

526
00:30:13,895 --> 00:30:17,558
of one particle, you affect the state of the other particle.

527
00:30:17,649 --> 00:30:19,059
You change its state.

528
00:30:19,192 --> 00:30:22,184
There's no forces or pulleys or, you know, telephone wires.

529
00:30:22,279 --> 00:30:24,144
There's nothing connecting those things, right.

530
00:30:24,239 --> 00:30:25,729
How could my choice to act here

531
00:30:25,866 --> 00:30:27,356
have anything to do with what happens over there?

532
00:30:27,451 --> 00:30:32,536
so there's no way they can communicate with each other.

533
00:30:32,622 --> 00:30:35,455
So it is completely bizarre.

534
00:30:35,584 --> 00:30:41,671
GSEENE:Einstein just could not accept entanglement worked this way,

535
00:30:41,757 --> 00:30:46,046
convincing himself that only the math was weird, not reality.

536
00:30:46,136 --> 00:30:48,923
He agreed that entangled particles could exist,

537
00:30:49,056 --> 00:30:52,014
but he thought that there was a simpler explanation

538
00:30:52,100 --> 00:30:54,432
for why they were linked that did not involve

539
00:30:54,561 --> 00:30:56,768
a mysterious long-distance connection.

540
00:30:56,897 --> 00:30:59,980
Instead, he insisted that entangled particles

541
00:31:00,108 --> 00:31:03,020
were more like a pair of gloves.

542
00:31:06,573 --> 00:31:08,780
Imagine someone separates the two gloves,

543
00:31:08,867 --> 00:31:10,573
putting each in a case.

544
00:31:16,458 --> 00:31:18,949
Then that person delivers one of those cases to me,

545
00:31:19,044 --> 00:31:22,161
and sends the other case

546
00:31:22,297 --> 00:31:23,127
to Antarctica.

547
00:31:29,096 --> 00:31:30,552
Thanks.

548
00:31:30,639 --> 00:31:33,472
Before I look inside my case,I know that it has

549
00:31:33,600 --> 00:31:36,012
either a left-hand or a right-hand glove.

550
00:31:36,144 --> 00:31:40,057
And when I open my case,if I find a left-hand glove,

551
00:31:40,148 --> 00:31:43,140
then at that instant,I know the case in Antarctica

552
00:31:43,276 --> 00:31:45,312
must contain a right-hand glove,

553
00:31:45,404 --> 00:31:49,488
even though no one has looked inside.

554
00:31:49,616 --> 00:31:52,824
There's nothing mysterious about this.

555
00:31:52,953 --> 00:31:54,818
Obviously, by looking inside the case,

556
00:31:54,955 --> 00:31:57,537
I've not affected either glove.

557
00:31:57,666 --> 00:31:59,031
This case has aways had a left-hand glove,

558
00:31:59,167 --> 00:32:00,498
and the one in Antarctica

559
00:32:00,627 --> 00:32:02,834
has always had a right-hand glove.

560
00:32:02,963 --> 00:32:04,419
That was set from the moment

561
00:32:04,506 --> 00:32:06,918
the gloves were separated and packed away.

562
00:32:07,008 --> 00:32:10,500
Now, Einstein thought that exactly the same idea

563
00:32:10,637 --> 00:32:12,844
applies to entangled particles.

564
00:32:12,973 --> 00:32:15,180
Whatever configuration the electrons are in

565
00:32:15,308 --> 00:32:17,139
must have been fully determined

566
00:32:17,227 --> 00:32:19,183
from the moment that they flew apart.

567
00:32:19,312 --> 00:32:22,224
So who was right?

568
00:32:22,357 --> 00:32:25,144
Bohr, who championed the equations that said

569
00:32:25,235 --> 00:32:27,351
that particles were like spinning wheel

570
00:32:27,446 --> 00:32:29,482
that could immediately link their random results

571
00:32:29,573 --> 00:32:32,110
even across great distances?

572
00:32:32,200 --> 00:32:36,239
Or Einstein, who believed there was no spooky connection,

573
00:32:36,371 --> 00:32:38,783
but instead, everything was decided

574
00:32:38,874 --> 00:32:43,493
well before you looked?

575
00:32:43,587 --> 00:32:45,873
Well, the big challenge in figuring out who was right,

576
00:32:46,006 --> 00:32:48,713
Bohr or Einstein,is that Einstein is saying

577
00:32:48,800 --> 00:32:52,964
a particle, say, has a definite spin before you measure it.

578
00:32:53,054 --> 00:32:55,670
"How do you check that?" you say to Einstein.

579
00:32:55,765 --> 00:32:57,050
He says, "Well, measure it

580
00:32:57,184 --> 00:32:59,266
and you'll find the definite spin."

581
00:32:59,394 --> 00:33:01,635
Bohr would say, "But it's the act of measurement

582
00:33:01,730 --> 00:33:03,891
that brought that spin to a definite state."

583
00:33:03,982 --> 00:33:07,566
No one knew how to resolve the problem,

584
00:33:07,652 --> 00:33:10,564
so the whole question came to be considered philosophy,

585
00:33:10,655 --> 00:33:13,237
not science.

586
00:33:13,366 --> 00:33:19,737
In 1955, Einstein died, still convinced that quantum mechanics

587
00:33:19,831 --> 00:33:24,325
offered, at best, an incomplete picture of reality.

588
00:33:30,300 --> 00:33:33,758
In 1967, at Columbia University,

589
00:33:33,845 --> 00:33:37,258
Einstein's mission to challenge quantum mechanics

590
00:33:37,349 --> 00:33:39,590
was taken up by an unlikely recruit.

591
00:33:39,726 --> 00:33:45,722
John Clauser was on the verge of earning a PhD in astrophysics.

592
00:33:45,815 --> 00:33:47,430
The only thing standing in his way

593
00:33:47,526 --> 00:33:49,562
was his grade in quantum mechanics.

594
00:33:49,653 --> 00:33:53,817
JOHN CLAUSER: When I was still a graduate student, try as I might,

595
00:33:53,949 --> 00:33:56,782
I could not understand quantum mechanics.

596
00:34:04,376 --> 00:34:06,662
GEEENE: Clauser was wondering if Einstein might be right

597
00:34:06,795 --> 00:34:09,332
when he made a life-altering discovery.

598
00:34:09,464 --> 00:34:11,455
It was an obscure paper

599
00:34:11,591 --> 00:34:16,836
by a little-known Irish physicist named John Bell.

600
00:34:16,972 --> 00:34:19,304
Amazingly, Bell seemed to have found a way

601
00:34:19,432 --> 00:34:21,889
to break the deadlock between Einstein and Bohr,

602
00:34:21,977 --> 00:34:26,311
and show, once and for all,

603
00:34:26,398 --> 00:34:28,810
who was right about the universe.

604
00:34:28,900 --> 00:34:32,017
CLAUSER:I was convinced that the quantum mechanical view

605
00:34:32,153 --> 00:34:33,984
was probably wrong.

606
00:34:34,072 --> 00:34:36,358
GREENE:Reading the paper,

607
00:34:36,491 --> 00:34:39,153
Clauser saw that Bell
had discovered

608
00:34:39,244 --> 00:34:41,485
how to tell if entangled particles

609
00:34:41,621 --> 00:34:43,737
were really communicating through spooky action,

610
00:34:43,832 --> 00:34:46,790
like matching spinning wheels,

611
00:34:46,876 --> 00:34:49,959
or if there was nothing spooky at all

612
00:34:50,046 --> 00:34:52,788
and the particles were already set in their ways,

613
00:34:52,882 --> 00:34:55,089
like e pair of gloves.

614
00:34:55,176 --> 00:34:57,883
What's more, with some clever mathematics,

615
00:34:58,013 --> 00:35:01,380
Bell showed that if spooky action were not at work,

616
00:35:01,516 --> 00:35:04,349
then quantum mechanics wasn't merely incomplete,

617
00:35:04,477 --> 00:35:06,183
as Einstein thought:

618
00:35:06,313 --> 00:35:09,601
it was wrong.

619
00:35:09,691 --> 00:35:11,932
I came to the conclusion that,"My God,

620
00:35:12,027 --> 00:35:15,019
this is one of the most profound results I've ever seen."

621
00:35:15,113 --> 00:35:17,229
GREENE:Bell was a theorist.

622
00:35:17,365 --> 00:35:20,607
But his paper showed that the question could be decided

623
00:35:20,702 --> 00:35:22,693
if you could build a machine

624
00:35:22,787 --> 00:35:28,327
that created and compared many pairs of entangled particles.

625
00:35:28,418 --> 00:35:32,081
Bell turned the question lnto an experimental question.

626
00:35:32,213 --> 00:35:33,874
It wasn't just going to be about philosophy

627
00:35:33,965 --> 00:35:35,421
or trading pieces of paper.

628
00:35:35,550 --> 00:35:39,042
And the experiment that he envisioned could be done.

629
00:35:39,179 --> 00:35:40,794
You could really set up an actual experiment

630
00:35:40,889 --> 00:35:42,254
to force the issue.

631
00:35:42,390 --> 00:35:46,224
GREENE:Clauser set about constructing a machine

632
00:35:46,311 --> 00:35:49,098
that would finally settle the debate.

633
00:35:49,230 --> 00:35:51,562
Now, I was just this punk graduate student at the time.

634
00:35:51,650 --> 00:35:55,188
This really seemed like,"Wow."

635
00:35:55,278 --> 00:35:56,734
There's always the slim chance

636
00:35:56,863 --> 00:36:01,903
that you will find a result that will shake the world.

637
00:36:13,963 --> 00:36:15,248
GREENE:Clauser's machine could measure

638
00:36:15,382 --> 00:36:17,998
thousands of pairs of entangled particles

639
00:36:18,093 --> 00:36:21,881
and compare their spins in many different directions.

640
00:36:25,225 --> 00:36:28,308
As the results started coming in,

641
00:36:28,436 --> 00:36:32,304
Clauser was surprised,and not happy.

642
00:36:32,440 --> 00:36:36,308
I kept asking myself,"What have I done wrong?

643
00:36:36,444 --> 00:36:39,026
What mistakes have I made in this?"

644
00:36:39,114 --> 00:36:43,107
GREENE:Clauser repeated his experiments, and soon,

645
00:36:43,201 --> 00:36:45,317
French physicist Alain Aspect

646
00:36:45,453 --> 00:36:47,569
started doing similar tests.

647
00:36:47,664 --> 00:36:50,121
Aspect got the same results.

648
00:36:53,962 --> 00:36:57,500
GREENE:Clauser's and Aspect's results are truly shocking

649
00:36:57,632 --> 00:36:59,748
Even though they defy our intuition,

650
00:36:59,843 --> 00:37:03,461
they prove that the math of quantum mechanics is right.

651
00:37:03,596 --> 00:37:06,633
Entanglement is reaL

652
00:37:06,725 --> 00:37:09,307
Quantum particles can be linked across space.

653
00:37:09,436 --> 00:37:12,394
Measuring one thing can,in fact,

654
00:37:12,480 --> 00:37:13,970
instantly affect its distant partner,

655
00:37:14,107 --> 00:37:17,770
as if the space between them didn't even exist.

656
00:37:17,861 --> 00:37:20,603
The one thing that Einstein thought was impossible,

657
00:37:20,697 --> 00:37:25,817
spooky action at a distance,actually happens.

658
00:37:25,952 --> 00:37:30,241
I was again very saddened

659
00:37:30,331 --> 00:37:32,413
that I had not overthrown quantum mechanics,

660
00:37:32,500 --> 00:37:35,663
because I still had and, to this day,

661
00:37:35,754 --> 00:37:37,995
still have great difficulty in understanding it.

662
00:37:38,131 --> 00:37:43,251
That is the most bizarre thing of quantum mechanics.

663
00:37:43,344 --> 00:37:46,256
It is impossible to even comprehend.

664
00:37:46,347 --> 00:37:48,463
Don't even ask me why.

665
00:37:48,558 --> 00:37:51,265
Don't ask me, which you're going to, how it works,

666
00:37:51,352 --> 00:37:53,809
because it's an illegal question.

667
00:37:53,897 --> 00:37:55,603
All we can say

668
00:37:55,690 --> 00:37:59,433
is that is apparently the way the world ticks.

669
00:37:59,527 --> 00:38:03,111
GREENE:So, if we accept that the world

670
00:38:03,198 --> 00:38:06,361
really does tick in this bizarre way,

671
00:38:06,451 --> 00:38:07,861
could we ever harness

672
00:38:07,952 --> 00:38:10,364
the long-distance spooky action of entanglement

673
00:38:10,497 --> 00:38:12,863
to do something useful?

674
00:38:12,957 --> 00:38:15,323
Well, one dream has been

675
00:38:15,418 --> 00:38:17,500
to somehow transport people and things

676
00:38:17,587 --> 00:38:19,373
from one place to another

677
00:38:19,464 --> 00:38:21,671
without crossing the space in between.

678
00:38:21,758 --> 00:38:24,215
In other words: teleportation.

679
00:38:24,344 --> 00:38:25,208
"Beam me aboard!"

680
00:38:25,303 --> 00:38:26,213
"Energize."

681
00:38:26,346 --> 00:38:28,712
"Energizing!"

682
00:38:28,848 --> 00:38:31,715
GREENE:Star Trek has aways made "beaming", or teleporting,

683
00:38:31,810 --> 00:38:33,596
look pretty convenient.

684
00:38:33,728 --> 00:38:35,593
It seems like pure science fiction,

685
00:38:35,730 --> 00:38:37,391
but could entanglement make it possible?

686
00:38:42,612 --> 00:38:44,694
Remarkably, tests are already underway

687
00:38:44,781 --> 00:38:49,400
here on the Canary islands, off the coast of Africa.

688
00:38:49,536 --> 00:38:54,280
ANTON ZEILINCER We do the experiments here on the Canary Islands

689
00:38:54,415 --> 00:38:57,202
because you have two observatories.

690
00:38:57,293 --> 00:38:58,749
And after all,it's a nice environment.

691
00:39:05,009 --> 00:39:07,751
GREENE:Anton Zeilinger is a long way from teleporting himself

692
00:39:07,887 --> 00:39:11,505
or any other human,

693
00:39:11,599 --> 00:39:14,215
but he is trying to use quantum entanglement

694
00:39:14,310 --> 00:39:18,519
to teleport tiny individual particles,

695
00:39:18,606 --> 00:39:21,188
in this case, photons, particles of light.

696
00:39:21,276 --> 00:39:26,145
He starts by generating a pair of entangled photons

697
00:39:26,281 --> 00:39:30,991
in a lab on the island of La Palma.

698
00:39:31,119 --> 00:39:33,485
One entangled photon stays on La Palma,

699
00:39:33,621 --> 00:39:36,078
while the other is sent by laser

700
00:39:36,165 --> 00:39:39,282
to the island of Tenerife, 89 miles away.

701
00:39:43,965 --> 00:39:45,546
Now, Zeilinger brings in a third photon,

702
00:39:45,633 --> 00:39:47,794
the one he wants to teleport,

703
00:39:47,886 --> 00:39:50,798
and has it interact with the entangled photon on La Palma.

704
00:39:53,266 --> 00:39:54,802
The team studies the interaction,

705
00:39:54,934 --> 00:39:57,676
comparing the quantum states of the two particles.

706
00:39:57,812 --> 00:39:59,803
And here's the amazing part:

707
00:39:59,898 --> 00:40:01,980
because of spooky action,

708
00:40:02,108 --> 00:40:04,520
Zeilinger is able to use that comparison

709
00:40:04,652 --> 00:40:09,021
to transform the entangled photon on the distant island

710
00:40:09,157 --> 00:40:11,614
into an identical copy of that third photon.

711
00:40:11,701 --> 00:40:15,114
It's as if the third photon has teleported across the sea,

712
00:40:15,204 --> 00:40:19,072
without traversing the space between the islands.

713
00:40:22,503 --> 00:40:24,664
We sort of extract the information

714
00:40:24,797 --> 00:40:26,662
carried by the original

715
00:40:26,799 --> 00:40:29,131
and make a new original there.

716
00:40:29,218 --> 00:40:31,675
GREENE:Using this technique,

717
00:40:31,763 --> 00:40:35,676
Zeilinger has successfully teleported dozens of particles.

718
00:40:41,773 --> 00:40:43,513
But could this go even further?

719
00:40:43,650 --> 00:40:44,981
Since we're made of particles,

720
00:40:45,068 --> 00:40:50,188
could this process make human teleportation possible one day?

721
00:40:58,706 --> 00:41:01,448
ATTENDANT:Welcome to New York City.

722
00:41:01,542 --> 00:41:04,329
Let's say I want to get to Paris for a quick lunch.

723
00:41:04,420 --> 00:41:05,910
Well, in theory,

724
00:41:06,047 --> 00:41:08,834
entanglement might someday make that possible.

725
00:41:08,925 --> 00:41:13,134
Here's what I'd need: a chamber of particles here in New York

726
00:41:13,221 --> 00:41:15,678
that's entangled with another chamber of particles in Paris.

727
00:41:19,435 --> 00:41:21,096
Right this way, Mr. Greene.

728
00:41:24,357 --> 00:41:25,893
GREENE: I would step into a pod

729
00:41:26,025 --> 00:41:28,311
that acts sort of like a scanner or a fax machine.

730
00:41:31,197 --> 00:41:34,405
While the device scans the huge number of particles in my body--

731
00:41:34,492 --> 00:41:36,232
more particles than there are stars

732
00:41:36,369 --> 00:41:38,155
in the observable universe--

733
00:41:38,246 --> 00:41:41,579
it's jointly scanning the particles in the other chamber,

734
00:41:41,708 --> 00:41:45,872
and it creates a list that compares the quantum state

735
00:41:45,962 --> 00:41:47,793
of the two sets of particles.

736
00:41:47,922 --> 00:41:52,837
And here's where entanglement comes in:

737
00:41:52,927 --> 00:41:54,963
because of spooky action at a distance,

738
00:41:55,096 --> 00:41:58,304
that list also reveals how the original state of my particles

739
00:41:58,433 --> 00:42:02,176
is related to the state of the particles in Paris.

740
00:42:04,022 --> 00:42:06,934
Next, the operator sends that list to Paris.

741
00:42:07,025 --> 00:42:08,561
There, they use the data

742
00:42:08,651 --> 00:42:11,108
to reconstruct the exact quantum state

743
00:42:11,195 --> 00:42:14,528
of every single one of my particles,

744
00:42:14,615 --> 00:42:16,731
and a new me materializes.

745
00:42:16,826 --> 00:42:22,287
It's not that the particles traveled from New York to Paris.

746
00:42:22,415 --> 00:42:24,531
it's that entanglement allows my quantum state

747
00:42:24,625 --> 00:42:29,494
to be extracted in New York and reconstituted in Paris,

748
00:42:29,630 --> 00:42:33,794
down to the last particle.

749
00:42:41,517 --> 00:42:42,552
Bonjour, Mr. Greene.

750
00:42:42,643 --> 00:42:43,849
Hi there.

751
00:42:43,978 --> 00:42:47,812
So here I am in Paris,an exact replica of myselt.

752
00:42:47,940 --> 00:42:52,149
And l'd better be, because measuring the quantum state

753
00:42:52,278 --> 00:42:57,193
of all my particles in New York has destroyed the original me.

754
00:42:57,325 --> 00:43:00,988
FARHI:It's absolutely required in the quantum teleportation protocal

755
00:43:01,120 --> 00:43:04,408
that the thing that is teleported

756
00:43:04,499 --> 00:43:06,911
is destroyed in the process.

757
00:43:07,001 --> 00:43:10,084
And yon know, that does make you a little anxious.

758
00:43:10,171 --> 00:43:13,129
I guess you would just end up being a lump

759
00:43:13,216 --> 00:43:18,006
of neutrons, protons, and electrons.

760
00:43:18,096 --> 00:43:19,836
You wouldn't look too good.

761
00:43:19,972 --> 00:43:23,885
Now, we are a long way from human teleportation today,

762
00:43:24,018 --> 00:43:26,680
but the possibility raises a question:

763
00:43:26,771 --> 00:43:30,263
is the Brian Greene who arrives in Paris really me?

764
00:43:30,358 --> 00:43:32,394
Well,there should be no difference

765
00:43:32,527 --> 00:43:36,896
between the old me in New York and the new me here in Paris.

766
00:43:37,031 --> 00:43:39,147
And the reason is that, accordindg to quantum mechanics,

767
00:43:39,242 --> 00:43:43,451
it's not the physical particles that make me "me",

768
00:43:43,538 --> 00:43:45,870
it's the information those particles contain.

769
00:43:45,957 --> 00:43:48,164
And that informatian has been teleported exactly

770
00:43:48,251 --> 00:43:51,209
for all the trillions of trillion of particles

771
00:43:51,337 --> 00:43:53,043
that make up my body.

772
00:43:53,172 --> 00:43:56,130
ZEILINGER:It is a very deep philosophical question,

773
00:43:56,217 --> 00:43:58,754
whether what arrives at the receiving station

774
00:43:58,886 --> 00:44:01,798
is the original or not.

775
00:44:01,889 --> 00:44:06,633
My position is that by original,

776
00:44:06,727 --> 00:44:09,309
we mean something which has all the properties of the original.

777
00:44:09,397 --> 00:44:10,512
ATTENDANT:Welcome to New York City.

778
00:44:10,606 --> 00:44:14,224
ZEILINGER:And if this is the case, then it is the original.

779
00:44:14,318 --> 00:44:16,775
I wouldn't step into that machine.

780
00:44:18,656 --> 00:44:21,363
Whether or not human teleportation

781
00:44:21,450 --> 00:44:23,532
ever becomes a reality,

782
00:44:23,619 --> 00:44:26,156
the fuzzy uncertainty of quantum mechanics

783
00:44:26,247 --> 00:44:29,865
has all sorts of other potential applications.

784
00:44:29,959 --> 00:44:34,749
Here at MIT, Seth Lloyd is one of many researchers

785
00:44:34,881 --> 00:44:38,169
trying to harness quantum mechanics in powerful new ways.

786
00:44:38,259 --> 00:44:40,875
LLOYD: Quantum mechanics is weird.

787
00:44:40,970 --> 00:44:42,255
That's just the way it is.

788
00:44:42,346 --> 00:44:44,678
So you know, life is dealing us weird lemons,

789
00:44:44,765 --> 00:44:47,381
can we make some weird lemonade from this?

790
00:44:47,476 --> 00:44:53,221
GREENE: Lloyd's weird lemonade comes in the form of a quantum computer.

791
00:44:53,316 --> 00:44:55,602
LLOYD: These are the guts of a quantum computer.

792
00:44:55,735 --> 00:44:59,102
GREENE: This gold and brass contraption

793
00:44:59,197 --> 00:45:01,438
might not look anything like your familiar laptop,

794
00:45:01,532 --> 00:45:07,994
but at its heart, it speaks the same language: binary code,

795
00:45:08,122 --> 00:45:13,958
a computer language spelled out in zeros and ones, called bits.

796
00:45:14,045 --> 00:45:18,664
LLOYD: so the smallest chunk of information is a bit.

797
00:45:18,799 --> 00:45:23,168
And what a computer does is simply busts up the information

798
00:45:23,304 --> 00:45:24,464
into the smallest chunks,

799
00:45:24,555 --> 00:45:25,795
and then flips them really, really, really rapidly.

800
00:45:25,890 --> 00:45:29,633
GREEDE:This quantum computer speaks in bits,

801
00:45:29,727 --> 00:45:31,934
but unlike a conventional bit,

802
00:45:32,021 --> 00:45:37,436
which at any moment can be either zero or one,

803
00:45:37,526 --> 00:45:39,642
a quantum bit is much more flexible.

804
00:45:39,779 --> 00:45:42,316
You know, something here can be a bit.

805
00:45:42,448 --> 00:45:45,986
Here is zero, there is one.

806
00:45:46,077 --> 00:45:48,159
That's a bit of information.

807
00:45:48,246 --> 00:45:50,828
So if you can have something that's here and there

808
00:45:50,957 --> 00:45:56,077
at the same time, then you have a quantum bit, or qubit.

809
00:45:56,170 --> 00:45:59,788
GREENE:Just as an electron can be a fuzzy mixture

810
00:45:59,882 --> 00:46:03,500
of spinning clockwise and counterclockwise,

811
00:46:03,636 --> 00:46:05,968
a quantum bit can be a fuzzy mixture

812
00:46:06,055 --> 00:46:11,175
of being a zero and a one, and so a qubit can multitask.

813
00:46:11,310 --> 00:46:12,891
LLOYD: Then it means you can do computations

814
00:46:13,020 --> 00:46:16,137
in ways that our classical brains

815
00:46:16,232 --> 00:46:18,314
could not have dreamed of.

816
00:46:18,401 --> 00:46:21,518
GREERE:In theory, quantum bits could be made from anything

817
00:46:21,654 --> 00:46:25,897
that acts in a quantum way,like an electron or an atom.

818
00:46:26,033 --> 00:46:28,695
The qubits at the heart of this computer

819
00:46:28,786 --> 00:46:31,027
are tiny super-conducting circuits

820
00:46:31,122 --> 00:46:32,703
built with nanotechnology

821
00:46:32,832 --> 00:46:35,198
that can run in two directions at once.

822
00:46:35,334 --> 00:46:37,916
Since quantum bits are so good at muti-tasking,

823
00:46:38,045 --> 00:46:40,707
if we can figure out

824
00:46:40,798 --> 00:46:43,380
how to get qubits to work together to solve problems,

825
00:46:43,467 --> 00:46:48,211
our computing power could explode exponentially.

826
00:46:50,391 --> 00:46:54,725
To get a feel for why a quantum computer would be so powerful

827
00:46:54,854 --> 00:46:59,473
imagine being trapped in the middle of a hedge maze.

828
00:47:08,492 --> 00:47:12,656
What you'd want is to find a way out as fast as possible.

829
00:47:12,747 --> 00:47:15,489
The problem is,there are so many options.

830
00:47:17,126 --> 00:47:18,741
And I just have to try them out one at a time.

831
00:47:22,798 --> 00:47:26,211
That means I'm going to hit lots of dead ends,

832
00:47:26,302 --> 00:47:29,169
go down lots of blind alleys,

833
00:47:29,263 --> 00:47:32,426
and make lots of wrong turns

834
00:47:32,516 --> 00:47:36,259
before I finally get lucky and find the exit.

835
00:47:36,395 --> 00:47:37,680
And that's pretty much

836
00:47:37,772 --> 00:47:39,933
how today's computers solve problems.

837
00:47:40,066 --> 00:47:42,523
Though they do it very quickly,

838
00:47:42,610 --> 00:47:45,647
they only carry out one task at a time,

839
00:47:45,780 --> 00:47:50,114
just like I can only investigate one path at a time in the maze.

840
00:47:50,201 --> 00:47:54,069
But if I could try all of the possibilities at once,

841
00:47:54,163 --> 00:47:55,778
it would be a different story.

842
00:47:55,915 --> 00:47:58,497
And that's kind of how quantun computing works.

843
00:48:01,962 --> 00:48:05,955
Since particles can, in a sense,be in many places at once,

844
00:48:06,050 --> 00:48:08,792
the computer could investigate a huge number of paths

845
00:48:08,928 --> 00:48:11,635
or solutions at the same time,

846
00:48:11,722 --> 00:48:15,681
and find the correct one in a snap.

847
00:48:15,810 --> 00:48:17,550
Now, a maze like this

848
00:48:17,645 --> 00:48:19,351
only has a limited number of routes to explore,

849
00:48:19,480 --> 00:48:20,515
so a conventional computer

850
00:48:20,648 --> 00:48:23,981
could find the way out pretty quickly.

851
00:48:24,068 --> 00:48:25,729
But imagne a problem

852
00:48:25,820 --> 00:48:30,280
with millions or billions of variables,

853
00:48:30,366 --> 00:48:32,652
like predicting the weather far in advance.

854
00:48:32,743 --> 00:48:35,405
We might be able to forecast natural disasters

855
00:48:35,496 --> 00:48:38,863
like earthquakes or tornadoes.

856
00:48:38,999 --> 00:48:42,116
Solving that kind of problem right now would be impossible,

857
00:48:42,211 --> 00:48:44,748
because it would take a ridiculously huge computer,

858
00:48:44,839 --> 00:48:47,831
but a quantum computer could get the job done

859
00:48:47,967 --> 00:48:50,674
with just a few hundred atoms.

860
00:48:50,761 --> 00:48:53,002
And so the brain of that computer...

861
00:48:53,139 --> 00:48:56,347
it would be smaller than a grain of sand.

862
00:48:59,019 --> 00:49:01,476
There's no doubt we're getting better and better

863
00:49:01,564 --> 00:49:04,977
at harnessing the power at the quantum world,

864
00:49:05,067 --> 00:49:06,682
and who knows where that could take us?

865
00:49:10,739 --> 00:49:12,855
But we can't forget that at the heart of this theory,

866
00:49:12,950 --> 00:49:18,115
which has given us so much,there is still a gaping hole.

867
00:49:18,205 --> 00:49:20,537
All the weirdness down at the quantum lever--

868
00:49:20,666 --> 00:49:23,499
at the scale of atoms and particles--

869
00:49:23,586 --> 00:49:26,202
where does the weirdness go?

870
00:49:26,338 --> 00:49:28,044
Why can things in the quantum world

871
00:49:28,174 --> 00:49:29,880
hover in a state of uncertainty,

872
00:49:30,009 --> 00:49:33,547
seemingly being partly here and partly there,

873
00:49:33,637 --> 00:49:36,970
with so many possibilities,while you and I--,

874
00:49:37,057 --> 00:49:39,719
who after all, are made of atoms and particles--

875
00:49:39,810 --> 00:49:44,554
seem to always be stuck in a single definite state?

876
00:49:44,648 --> 00:49:48,311
We are always either here or there.

877
00:49:48,402 --> 00:49:52,236
Niels Bohr offered no real explanation

878
00:49:52,364 --> 00:49:55,276
for why all the weird fuzziness of the quantum world

879
00:49:55,409 --> 00:49:59,402
seems to vanish as things increase in size.

880
00:50:01,373 --> 00:50:03,034
As powerful and accurate

881
00:50:03,125 --> 00:50:05,616
as quantum mechanics has proven to be,

882
00:50:05,753 --> 00:50:10,588
scientists are stll struggling to figure this out.

883
00:50:10,674 --> 00:50:13,211
Some believe that there is some detail missing

884
00:50:13,302 --> 00:50:15,793
in the equations of quantum mechanics.

885
00:50:15,930 --> 00:50:19,343
And so, even though there are multiple possibilities

886
00:50:19,433 --> 00:50:23,096
in the tiny world, the missing details would adjust the numbers

887
00:50:23,229 --> 00:50:27,393
on our way up from atoms to objects in the big world

888
00:50:27,483 --> 00:50:29,269
so that it would become clear

889
00:50:29,360 --> 00:50:32,443
that all but one of those possibilities disappear,

890
00:50:32,571 --> 00:50:37,361
resulting in a single,certain outcome.

891
00:50:37,451 --> 00:50:40,864
Other physicists believe that all the possibilities

892
00:50:40,955 --> 00:50:44,493
that exist in the quantum world,they never do go away.

893
00:50:44,625 --> 00:50:48,834
Instead, each and every possible outcome actually happens,

894
00:50:48,963 --> 00:50:52,000
only most of them happen

895
00:50:52,132 --> 00:50:55,499
in other universes parallel to our own.

896
00:50:55,636 --> 00:50:59,504
It's a mind-blowing idea,

897
00:50:59,640 --> 00:51:03,974
but reality could go beyond the one universe we all see

898
00:51:04,103 --> 00:51:05,593
and be constantly branching off,

899
00:51:05,688 --> 00:51:07,770
creating new,alternative worlds,

900
00:51:07,856 --> 00:51:12,771
where every possibility gets played out.

901
00:51:12,861 --> 00:51:14,852
This is the frontier of quantum mechanics,

902
00:51:14,989 --> 00:51:19,949
and no one knows where it will lead.

903
00:51:20,035 --> 00:51:23,152
The very fact that our reality is much grander than we thought,

904
00:51:23,247 --> 00:51:26,831
much more strange and mysterious than we thought,

905
00:51:26,959 --> 00:51:31,749
is to me also very beautiful and awe-inspiring.

906
00:51:31,839 --> 00:51:36,833
The beauty of science is that it allows you to learn things

907
00:51:36,927 --> 00:51:39,509
which go beyond your wildest dreams.

908
00:51:39,638 --> 00:51:42,596
And quantum mechanics is the epitome of that.

909
00:51:42,683 --> 00:51:44,844
After you learn quantum mechanics,

910
00:51:44,935 --> 00:51:48,268
you're never really the same again.

911
00:51:51,734 --> 00:51:54,100
GREENE: As strange as quantum mechanics may be,

912
00:51:54,194 --> 00:51:56,310
what's now clear is that there's no boundary

913
00:51:56,405 --> 00:51:58,316
between the worlds of the tiny and the big.

914
00:51:58,407 --> 00:52:02,821
Instead, these laws apply everywhere,

915
00:52:02,911 --> 00:52:06,119
and it's just that their weird features are most apparent

916
00:52:06,206 --> 00:52:08,538
when things are small.

917
00:52:08,626 --> 00:52:10,537
And so the discovery of quantum mechanics

918
00:52:10,628 --> 00:52:14,086
has revealed a reality,our reality,

919
00:52:14,214 --> 00:52:16,375
that's both shocking and thrilling,

920
00:52:16,508 --> 00:52:19,375
bringing us that much closer to fully understanding

921
00:52:19,511 --> 00:52:22,093
the fabric of the cosmos.

922
00:52:39,573 --> 00:52:42,064
Major funding for NOVA is provided by:

923
00:52:44,536 --> 00:52:45,901
And...

924
00:52:56,674 --> 00:53:00,087
And by the Corporation for Public Broadcasting

925
00:53:00,177 --> 00:53:04,420
and by contributions to your PBS station from:

926
00:53:11,063 --> 00:53:13,725
Major funding for "the Fabric of the Cosmos"

927
00:53:13,816 --> 00:53:16,432
is provided by the National Science Foundation.

928
00:53:24,201 --> 00:53:25,737
And...

929
00:53:28,789 --> 00:53:31,622
Supporting original research and public understanding

930
00:53:31,709 --> 00:53:37,579
of science, technology,engineering and mathematics.

931
00:53:37,673 --> 00:53:39,584
Additional funding
is provided by...

932
00:53:51,478 --> 00:53:53,469
And the George D. Smith Fund.

933
00:53:56,442 --> 00:53:59,149
Captioned by Media Access Group at WGBH access.wgbh.org