Original subtitles

Lying just beneatheveryday reality

is a breathtaking world,

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

Physicist and best-selling author Brian Greene takes you

on a journey that bends the rules of human experience.

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

According to the laws of physics, this can happen.

It's a world that comes to light

as we probe the most extreme realms of fhe cosmos,

from black holes to the Big Bang

to the very heart of matter itself.

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

Here, our universe may be one of numerous parallel realities

The three-dimensional world may be just an illusion,

and there's no distinction

between past, present and future.

GREENE: But how could this be?

How could we be so wrong about something so familiar?

Does it bother us?

Absolutely.

There's no principle built into the laws ot nature

that say that theoretical physicists have to be happy.

It's a game-changing perspective

that opens up a new world of posibilities.

Coming up...

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

The laws here seem impossible.

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

to just one location.

Yet they're vital to everything in the universe.

There's no disagreement between quantum mechanics

and any experiment that's ever been done.

What do they reveal about the nature of reality?

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

right now on NOVA.

Major funding for NOVA is provided by the following:

And...

And by the Corporation for Public Broadcasting

and by contributions to your PBS station form ;

Major funding for "The Fabric of the Cosmos"

is provided by the National Science Foundation.

And...

Supporting original research and public understanding

of science, technology, engineering and mathematics.

Additional funding is provided by...

And the George D. Smith Fund.

GREENE: For thousands of years,

we've been tryind to unlock

the mysteries of how the universe works.

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

that describes the clear and certain motion

of galaxies and stars and planets.

But now we know, at a fundamental level

things are a lot were fuzzy,

because we've discovered a revolutionary new set of laws

that have completely transformed our picture of the universe.

From outer space, to the heart of New York city

to the microscopic realm,

our view of the world has shifted,

thanks to these strange and mysterious laws

that are redefining our understanding of reality.

Thay are the laws of quantum mechanics.

Quantum mechanics rules over every atom and tiny particle

in every piece of matter.

In stars and planets,

in rocks and buildings,

and in you and me.

We don't notice the strangeness of quantum mechanics

in everyday life,

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

You just have to change your perspective

and get down to the tiniest of scales,

to the level of atoms and the particles inside them.

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

appear completely different from the familiar laws

that govern big, everyday objects.

And once you catch a glimpse of them,

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

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

down at the smallest of scales.

But what if you could visit a place like this,

where the quantum laws were obvious,

where people and objects behave like tiny atoms and particles?

You'd be in for quite a show.

Here, objects do things that seem crazy.

I mean, in the quantum world,

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

to just one location,

or to follow just one path.

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

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

even if there's no one there.

And here's one of the strangest things of all

if people behaved like the particles inside the atom,

then most of the time,

you wouldn;t knom exactly where they were.

Instead, they could be almost anywhere,

until you look for them.

Hey.

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

So why do we believe these bizarre laws?

Well, for over 75 years,

we've been using them to make predictions

for how atoms and particles should behave.

And in experiment after experiment,

the quantum laws have always been right.

It's the best theory we have.

There are literally billions of pieces

of confirming evidence for quantum mechanics.

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

There's no disagreement between quantum mechanics

and any enperiment that's ever been done.

The quantum laws become most obvious

when you get down to tiny scales, like atoms,

but consider this,

Im made of atoms.

So are you.

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

So it must be the case that these weird quantum laws

are not just telling us about small things.

They're telling us about reality.

So how did we discover them,

these strange laws that seem to contradict

much of what we thought we knew about the universe

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

The rules that govern how planets orbit the sun.

How a ball arcs through the sky.

How ripples move across the surface of a pond.

These laws were all spelled out in a series of equations

called classical mechanics,

and they allowed us to predict

the behavior of things with certainty.

It all seemed to be making perfect sense

until about a hundred years ago,

when scientists were struggling to explain

some unusual properties of light.

In particular, the kind of light that glowed from gases

when they were heated in a glass tube.

When scientists observed this light through a prism,

they saw something they'd never expected.

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

it formed lines.

Not the continuous spectrum that you see projected

by a piece of cut glass on your table,

but very distinct lines.

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

kind of complete rainbow of light.

It would give out sort of pencil beams of light

at very specific colors.

GALISON:And it was something of a mystery,

how to understand what was going on.

GREENE: An explanation for the mysterious lines of color

would come from a band of radical scientists

who, at the begining of the 20th century,

were grappling with the fundamental nature

of the physical world.

And some of the most startling insights

come from the mind of Niels Bohr,

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

Bohr was convinced that the solution to the mystery

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

He thought that atoms resemble tiny solar systems,

with even tinier particles called electrons

orbiting around a nucleus,

much the way the planets orbit around the sun.

But unlike the solar system,Bohr proposed that electrons

could not move in just any orbit.

Instead, only certain orbits were allowed.

GALISON:And he had a really surprising

and completely counterphysical idea,

which was that there were definite states,

fixed orbits that these electrons could have,

and only those orbits.

GREENE:Bohr said that when an atow was heated,

its electrons would become agitated

and leap from one fixed orbit to another.

Each downward leap would emit energy in the form of light

in very specific wavelengths,

and thats why atoms produce very specific colors.

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

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

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

as it got excited or de-excited.

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

You see very sharp reds and very sharp greens.

It's the quantum leap

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

GREENE:What made the quantum leap so surprising

was that the electron goes direcity from here to there,

seemingly without moving through the space in between.

It was as if Mars suddenly popped from its own orbit

out to Jupiter.

Bohr argued that the quantum leap arises from a fundamental

and fundamentally weird,property of electrons in atoms,

that their energy comes in discrete chunks

that can't be subdivided,

specific minmum quantities called "quanta".

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

that electrons can occupy.

KAISER:An electron had to be here or there,

and simply nowhere in between.

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

Think of your daily life.

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

Do you think that you have to take

a certain amount of minimum food?

Food is not quantized.

But the energy of eleotrons in an atom are quantized.

That is very mysterious,why that is.

GREENE:As mysterious as it might be

far tiny particles in an atom to act this way,

the evidence quickly mounted,showing that Bohr was right.

In more and more experiments,

electrons follewed a different set of rules

than planets or png-pong balls.

Bohr's discovery was a game-changer.

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

found themselves on a collision course

with the accepted laws of physics.

The quantum leap was just the begining.

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

with one of the greatest physicist in history

Albert Einstein was not afraid of new ideas.

But during the 1920s,the world of quantum mechanics

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

a direction that sharp diverged

from the absolute,definitive predictions

that were the hallmark of classcal physics.

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

what it was that distinguished physics

from all kind of flaky speculation,

they would have said,

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

And quantum mechanics

seemed to pull the rug out from under that.

GREENE:One test in particular,

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

exposed quantum mysteries like no other.

If you were looking for a description of reality

based on certainty, your expectations would be shattered.

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

and how dramatically it alters our picture of reality,

by carrying out a similar xperiment,

not on the scale of tiny particles

but on the scale of more ordinary objects,

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

But first I need to make

a couple of adjustments to the lane.

You'd expect that if I roll

a few of these balls down the lane,

they'll either be stopped by the barrier

or pass through one or the other slit

and hit the screen at the back.

And in fact,that's just what happens.

Those balls that make it through always hit the screen

directly behind either the left slit or the right slit.

The double slit experiment was much like this,

except instead of bowling balls,

you use electrons, which are billions of times smaller.

you can picture them like this.

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

When electrons are hurled at the two slits,

something very different happens on the other side.

Instead of hitting just two areas,

the electrons land all over the detector screen,

creating a pattern of stripes,

including some right between the two slits,

the very place you'd think would be blocked.

So what's going on?

Well, to physicists,even in the 1920s,

this pattern could mean only one thing:

waves.

Waves do all kinds of interesting things,

thigs that bowling balls would never do.

They can split.

They can combine.

If I sent a wave at water through the double slits,

it would split in two,

and then the two sets of waves would intersect.

Their peaks and valleys would combine,

getting bigger in some places,smaller in others,

and sometimes they'd cancel each other out.

With the height of the water

corresponding to brightness on the screen,

the peaks and valleys would create a series of stripes

in what'known as an interference pattern.

So how could electrons,which are particles,

form that pattern?

How could a single electron end up in places a wave would go?

Particles are particles.

Waves are waves.

How can a particle be a wave?

Unless you give up the idea that it's a particle.

And think, "Aha!"

This thing that I thought was a particle was actually a wave.

A wave in an ocean,that's not a particle.

The ocean is made out of particles,

but the waves in the ocean are not particles.

And rocks are not waves,rocks are rocks.

so a rock is an example of a particle,

an ocean wave is an example of an ocean wave,

and now somebody's telling you a rock is like an ocean wave.

What?

Back in the 1920s,

when a version of this experiment was first done,

scientists struggled to understand this wavy behavior.

Some wondered if a singe electron, while in motion,

might spread out into a wave.

And the physicist Erwin Schrodinger

came up with an equation that seemed to descride it.

STEVEN WEINBERG: Schrodinger thought that this wave

was a description of an extended electron,

that somehow an electron got smeared out

and it was no longer a point,but was like a mush.

There was a lot of argument

about exactly what this represented.

GREENE Finally, a physicist named Max Born

came up with a new and revolutionary idea

for what the wave equation described.

Born said that the wave is not a smeared-out electron

or anything else previously encountered in science.

Instead, he declared it's something

that's really peculiar:a probability wave.

That is, Born argued that the size of the wave at any location

predicts the likelihood of the electron being found there.

WEINBERG:Where the wave is big,

that's net where most of the electron is,

that's where the electron is most likely to be.

And that's just very strange, right?

So the electron on its own seems to be a jumble of possibilities.

PETER FISHER:You're not allowed to ask,

"Where is the electron right now?"

You are allowed to ask,"If I look for the electron

"in this little particular part of space,

what is the likelihood I will find it there?"

I mean, that bugs anyone anytime.

As weird as it sounds,

this new way of describing how particles like electrons move

is actually right.

When I throw a single electron,

I can never predict where it will land,

but if I use schrodinger's equation

to find the electron's probability wave,

I can predict with great certainty

that if I throw enough electrons,

then, say, 33.1% would end up "here,"

7.9% would end up "there,"and so on.

These kinds of predictions

have been confirmed again and again by experiments.

And so, the equations of quantum mechanics

turn out to be amazingly accurate and precise,

so long as you can accept that it's all about probability.

If you think that probability means

you're reduced to guessing,

the casinos of Las Vegas are ready to prove you wrong.

Try your hand at any one of these games of chance,

and you can see the power of probability.

Let's say I place a $20 bet on number 29

here at the roulette table.

The house doesn't know whether I'll win on this spin

or the next or the next.

One.

But it does know the probability that I'll win.

In this game,it's one in 38.

21.

(bell rings)

WOMAN:29.

So even though I may win now and then, in the long run,

the house always takes in more than it loses.

The point is, the house doesn't have to know the outcome

at any single card game,roll of the dice,

or spin of the roulette wheel

Casinos can still be confident that over the course

of thousands of spins, deals,and rolls, they will win,

and they can predict with exquisite accuracy

exactly how often.

According to quantum mechanics,

the world itself is a game of chance much like this.

All the matter in the universe

is made of atoms and subatomic particles

that are ruled by probability,not certainty.

EDWARD FARHI:At base, nature is described

by an inherently probabilistic theory.

And that is highly counterintuitive,

and something which many people would find difficulty accepting.

GREENE: One person who found it difficult was Einstein.

Einstein could not believe that the fundamental nature

of reality, at the deepest lever, was determined by chance.

And this is what Einstein could not accept.

Einstein said,"God does not throw dice."

He didn't like the idea that we couldn't with certainty say,

"This happens or that happens."

GREENE: But a lot of other physicists

weren't so put off by probability,

because the equations at quantum mechanics

gave them the power to predict the behavior

of groups of atoms and tiny particles

with astounding precision.

Before long.that power would lead

to some very big inventions.

Lasers, transistors,the integrated circuit,

the entire field of electronics.

MAX TEGMARK:If quantum mechanics suddenly went on strike,

every single machine that we have in the US, almost,

would stop functioning.

GREENE:The equations of quantum mechanics

would help engineers design microscopic switches

that direct the flow of tiny electrons

and control virtually every one of today's computers,

digital cameras,and telephones.

ADAMS: All the devices that we live on,diodes, transistors, just...

that form the basis of information technology,

the basis of daily life in all sorts of ways, they work.

And why do they work?

They work because of quantum mechanics.

WEINBERG:l'm tempted to say that without quantum mechanics,

we'd be back in the dark ages,but I guess more accurately,

without quantum mechanics we'd be back in the 19th century.

Steam engines,telegraph signals.

TEGMARK: Quantum mechanics is the most successful theory

that we physicists have ever discovered.

And yet, we're still arguing

about what it means,

what it tells us about the nature at reality.

GREENE:In spite of all of its triumphs,

quantum mechanics remains deeply mysterious.

It makes all this stuff run,but we still haven't answered

basic questions raised by Albert Einstein

at the way back in the 1920s and '30s,

questions involving probability and measurement,

the act of observation.

For Niels Bohr, measurement changes everything.

He believed that before you measured or observed a particle,

its characteristics were uncertain.

For example, an electron in the double-slit experiment.

Before the detector at the back pinpoints its location,

it could be almost anywhere,

with a whole range of possibilities.

Until the moment you observe it,and only at that point,

will the location's uncertainty disappear.

According to Bohr's approach to quantum mechanics,

when you measure a particle,

the act at measurement forces the particle to relinquish

all of the possible places it could have been

and select one definite location where yon find it.

The act of measurement is what forces the particle

to make that choice.

Niels Bohr accepted that the nature of reality

was inherently fuzzy.

But not Einstein.

He believed in certainty,

not just when something is measured or looked at,

but all the time.

As Einstein said, "I like to think the moon is there

even when I'm not lookng at it."

That's what Einstein was so upset about.

Do we really think the reality of the universe rests on

whether or not we happen to open our eyes?

That's just bizarre.

GREENE:Einstein was convinced something was missing from quantum theory,

something that would describe

all the detailed features of particles, like their locations,

even when you were not looking at them.

But at the time, few physicists shared his concern.

KAISER:And Einstein just thought it was giving up

on the job of the physicist.

It wasn't bad physics per se,it just was totally incomplete.

That's Einstein's refrain.

Quantum mechanics is not incorrect,it's as for as...

in so far as it goes,but it's incomplete.

It doesn't capture all of the things

that cau be said or predicted with certainty.

GBEENE:Despite Einstein's arguments,Niels Bohr remained unmoved.

When Einstein repeated that "God does not play dice,"

Bohr responded,"Stop telling God what to do."

But in 1935, Einstein thought he'd finally found

the Achilles' Heel of quantum mechanics.

Something so strange,

so counter to all logical views of the universe,

he thought it held the key

to proving the theory was incomplete.

It's called "entanglement."

LEWIN: The most bizarre,

the most absurd, the most crazy,the most ridiculous prediction

that quantum mechanics makes is entanglement.

GREENE:Entanglement is a theoretical prediction

that comes from the equations of quantum mechanics.

Two particles can become entangled

if they're close together and their properties become in linked.

Remarkably,quantum mechanics says

that even if you separated those particles,

sending them in opposite directions,

they could remain entangled,inextricably connected.

To understand how profoundly weird this is,

consider a property of electrons called "spin."

Unlike a spinning top,an electron's spin,

as with other quantum qualities,

is generlly completely fuzzy and uncertain

untill the moment you measure it.

And when you do, you'll find

it's either spinning clockwise or counterclockwise.

It's kind of like this wheel.

When it stops turning,

it will randomly land on either red or blue.

Now imagine a second wheel.

If these two wheels behaved like two entangled electrons,

then every time one landed red,

the other is guaranteed to land on blue.

And vice-versa.

Now, since the wheels are not connected,

that's suspicious enough.

But the quantum mechanics embraced by Nieh Bohr

and his colleagues went even further,

predicting that if one of the pair were far away,

even on the moon, with no wires or transmitters connecting them,

still, if you look at one and find red,

the other is sure to be blue.

ln other words, if you measured a particle here,

not only would you affect it,

but your measurement would also affect its entangled partner,

no matter how distant.

For Einstein, that kind of weird long-range connection

between spinning wheels or particles was so ludicrous,

he called it spooky:"spooky action at a distance."

What's surprising is that when you make a measurement

of one particle, you affect the state of the other particle.

You change its state.

There's no forces or pulleys or, you know, telephone wires.

There's nothing connecting those things, right.

How could my choice to act here

have anything to do with what happens over there?

so there's no way they can communicate with each other.

So it is completely bizarre.

GSEENE:Einstein just could not accept entanglement worked this way,

convincing himself that only the math was weird, not reality.

He agreed that entangled particles could exist,

but he thought that there was a simpler explanation

for why they were linked that did not involve

a mysterious long-distance connection.

Instead, he insisted that entangled particles

were more like a pair of gloves.

Imagine someone separates the two gloves,

putting each in a case.

Then that person delivers one of those cases to me,

and sends the other case

to Antarctica.

Thanks.

Before I look inside my case,I know that it has

either a left-hand or a right-hand glove.

And when I open my case,if I find a left-hand glove,

then at that instant,I know the case in Antarctica

must contain a right-hand glove,

even though no one has looked inside.

There's nothing mysterious about this.

Obviously, by looking inside the case,

I've not affected either glove.

This case has aways had a left-hand glove,

and the one in Antarctica

has always had a right-hand glove.

That was set from the moment

the gloves were separated and packed away.

Now, Einstein thought that exactly the same idea

applies to entangled particles.

Whatever configuration the electrons are in

must have been fully determined

from the moment that they flew apart.

So who was right?

Bohr, who championed the equations that said

that particles were like spinning wheel

that could immediately link their random results

even across great distances?

Or Einstein, who believed there was no spooky connection,

but instead, everything was decided

well before you looked?

Well, the big challenge in figuring out who was right,

Bohr or Einstein,is that Einstein is saying

a particle, say, has a definite spin before you measure it.

"How do you check that?" you say to Einstein.

He says, "Well, measure it

and you'll find the definite spin."

Bohr would say, "But it's the act of measurement

that brought that spin to a definite state."

No one knew how to resolve the problem,

so the whole question came to be considered philosophy,

not science.

In 1955, Einstein died, still convinced that quantum mechanics

offered, at best, an incomplete picture of reality.

In 1967, at Columbia University,

Einstein's mission to challenge quantum mechanics

was taken up by an unlikely recruit.

John Clauser was on the verge of earning a PhD in astrophysics.

The only thing standing in his way

was his grade in quantum mechanics.

JOHN CLAUSER: When I was still a graduate student, try as I might,

I could not understand quantum mechanics.

GEEENE: Clauser was wondering if Einstein might be right

when he made a life-altering discovery.

It was an obscure paper

by a little-known Irish physicist named John Bell.

Amazingly, Bell seemed to have found a way

to break the deadlock between Einstein and Bohr,

and show, once and for all,

who was right about the universe.

CLAUSER:I was convinced that the quantum mechanical view

was probably wrong.

GREENE:Reading the paper,

Clauser saw that Bell had discovered

how to tell if entangled particles

were really communicating through spooky action,

like matching spinning wheels,

or if there was nothing spooky at all

and the particles were already set in their ways,

like e pair of gloves.

What's more, with some clever mathematics,

Bell showed that if spooky action were not at work,

then quantum mechanics wasn't merely incomplete,

as Einstein thought:

it was wrong.

I came to the conclusion that,"My God,

this is one of the most profound results I've ever seen."

GREENE:Bell was a theorist.

But his paper showed that the question could be decided

if you could build a machine

that created and compared many pairs of entangled particles.

Bell turned the question lnto an experimental question.

It wasn't just going to be about philosophy

or trading pieces of paper.

And the experiment that he envisioned could be done.

You could really set up an actual experiment

to force the issue.

GREENE:Clauser set about constructing a machine

that would finally settle the debate.

Now, I was just this punk graduate student at the time.

This really seemed like,"Wow."

There's always the slim chance

that you will find a result that will shake the world.

GREENE:Clauser's machine could measure

thousands of pairs of entangled particles

and compare their spins in many different directions.

As the results started coming in,

Clauser was surprised,and not happy.

I kept asking myself,"What have I done wrong?

What mistakes have I made in this?"

GREENE:Clauser repeated his experiments, and soon,

French physicist Alain Aspect

started doing similar tests.

Aspect got the same results.

GREENE:Clauser's and Aspect's results are truly shocking

Even though they defy our intuition,

they prove that the math of quantum mechanics is right.

Entanglement is reaL

Quantum particles can be linked across space.

Measuring one thing can,in fact,

instantly affect its distant partner,

as if the space between them didn't even exist.

The one thing that Einstein thought was impossible,

spooky action at a distance,actually happens.

I was again very saddened

that I had not overthrown quantum mechanics,

because I still had and, to this day,

still have great difficulty in understanding it.

That is the most bizarre thing of quantum mechanics.

It is impossible to even comprehend.

Don't even ask me why.

Don't ask me, which you're going to, how it works,

because it's an illegal question.

All we can say

is that is apparently the way the world ticks.

GREENE:So, if we accept that the world

really does tick in this bizarre way,

could we ever harness

the long-distance spooky action of entanglement

to do something useful?

Well, one dream has been

to somehow transport people and things

from one place to another

without crossing the space in between.

In other words: teleportation.

"Beam me aboard!"

"Energize."

"Energizing!"

GREENE:Star Trek has aways made "beaming", or teleporting,

look pretty convenient.

It seems like pure science fiction,

but could entanglement make it possible?

Remarkably, tests are already underway

here on the Canary islands, off the coast of Africa.

ANTON ZEILINCER We do the experiments here on the Canary Islands

because you have two observatories.

And after all,it's a nice environment.

GREENE:Anton Zeilinger is a long way from teleporting himself

or any other human,

but he is trying to use quantum entanglement

to teleport tiny individual particles,

in this case, photons, particles of light.

He starts by generating a pair of entangled photons

in a lab on the island of La Palma.

One entangled photon stays on La Palma,

while the other is sent by laser

to the island of Tenerife, 89 miles away.

Now, Zeilinger brings in a third photon,

the one he wants to teleport,

and has it interact with the entangled photon on La Palma.

The team studies the interaction,

comparing the quantum states of the two particles.

And here's the amazing part:

because of spooky action,

Zeilinger is able to use that comparison

to transform the entangled photon on the distant island

into an identical copy of that third photon.

It's as if the third photon has teleported across the sea,

without traversing the space between the islands.

We sort of extract the information

carried by the original

and make a new original there.

GREENE:Using this technique,

Zeilinger has successfully teleported dozens of particles.

But could this go even further?

Since we're made of particles,

could this process make human teleportation possible one day?

ATTENDANT:Welcome to New York City.

Let's say I want to get to Paris for a quick lunch.

Well, in theory,

entanglement might someday make that possible.

Here's what I'd need: a chamber of particles here in New York

that's entangled with another chamber of particles in Paris.

Right this way, Mr. Greene.

GREENE: I would step into a pod

that acts sort of like a scanner or a fax machine.

While the device scans the huge number of particles in my body--

more particles than there are stars

in the observable universe--

it's jointly scanning the particles in the other chamber,

and it creates a list that compares the quantum state

of the two sets of particles.

And here's where entanglement comes in:

because of spooky action at a distance,

that list also reveals how the original state of my particles

is related to the state of the particles in Paris.

Next, the operator sends that list to Paris.

There, they use the data

to reconstruct the exact quantum state

of every single one of my particles,

and a new me materializes.

It's not that the particles traveled from New York to Paris.

it's that entanglement allows my quantum state

to be extracted in New York and reconstituted in Paris,

down to the last particle.

Bonjour, Mr. Greene.

Hi there.

So here I am in Paris,an exact replica of myselt.

And l'd better be, because measuring the quantum state

of all my particles in New York has destroyed the original me.

FARHI:It's absolutely required in the quantum teleportation protocal

that the thing that is teleported

is destroyed in the process.

And yon know, that does make you a little anxious.

I guess you would just end up being a lump

of neutrons, protons, and electrons.

You wouldn't look too good.

Now, we are a long way from human teleportation today,

but the possibility raises a question:

is the Brian Greene who arrives in Paris really me?

Well,there should be no difference

between the old me in New York and the new me here in Paris.

And the reason is that, accordindg to quantum mechanics,

it's not the physical particles that make me "me",

it's the information those particles contain.

And that informatian has been teleported exactly

for all the trillions of trillion of particles

that make up my body.

ZEILINGER:It is a very deep philosophical question,

whether what arrives at the receiving station

is the original or not.

My position is that by original,

we mean something which has all the properties of the original.

ATTENDANT:Welcome to New York City.

ZEILINGER:And if this is the case, then it is the original.

I wouldn't step into that machine.

Whether or not human teleportation

ever becomes a reality,

the fuzzy uncertainty of quantum mechanics

has all sorts of other potential applications.

Here at MIT, Seth Lloyd is one of many researchers

trying to harness quantum mechanics in powerful new ways.

LLOYD: Quantum mechanics is weird.

That's just the way it is.

So you know, life is dealing us weird lemons,

can we make some weird lemonade from this?

GREENE: Lloyd's weird lemonade comes in the form of a quantum computer.

LLOYD: These are the guts of a quantum computer.

GREENE: This gold and brass contraption

might not look anything like your familiar laptop,

but at its heart, it speaks the same language: binary code,

a computer language spelled out in zeros and ones, called bits.

LLOYD: so the smallest chunk of information is a bit.

And what a computer does is simply busts up the information

into the smallest chunks,

and then flips them really, really, really rapidly.

GREEDE:This quantum computer speaks in bits,

but unlike a conventional bit,

which at any moment can be either zero or one,

a quantum bit is much more flexible.

You know, something here can be a bit.

Here is zero, there is one.

That's a bit of information.

So if you can have something that's here and there

at the same time, then you have a quantum bit, or qubit.

GREENE:Just as an electron can be a fuzzy mixture

of spinning clockwise and counterclockwise,

a quantum bit can be a fuzzy mixture

of being a zero and a one, and so a qubit can multitask.

LLOYD: Then it means you can do computations

in ways that our classical brains

could not have dreamed of.

GREERE:In theory, quantum bits could be made from anything

that acts in a quantum way,like an electron or an atom.

The qubits at the heart of this computer

are tiny super-conducting circuits

built with nanotechnology

that can run in two directions at once.

Since quantum bits are so good at muti-tasking,

if we can figure out

how to get qubits to work together to solve problems,

our computing power could explode exponentially.

To get a feel for why a quantum computer would be so powerful

imagine being trapped in the middle of a hedge maze.

What you'd want is to find a way out as fast as possible.

The problem is,there are so many options.

And I just have to try them out one at a time.

That means I'm going to hit lots of dead ends,

go down lots of blind alleys,

and make lots of wrong turns

before I finally get lucky and find the exit.

And that's pretty much

how today's computers solve problems.

Though they do it very quickly,

they only carry out one task at a time,

just like I can only investigate one path at a time in the maze.

But if I could try all of the possibilities at once,

it would be a different story.

And that's kind of how quantun computing works.

Since particles can, in a sense,be in many places at once,

the computer could investigate a huge number of paths

or solutions at the same time,

and find the correct one in a snap.

Now, a maze like this

only has a limited number of routes to explore,

so a conventional computer

could find the way out pretty quickly.

But imagne a problem

with millions or billions of variables,

like predicting the weather far in advance.

We might be able to forecast natural disasters

like earthquakes or tornadoes.

Solving that kind of problem right now would be impossible,

because it would take a ridiculously huge computer,

but a quantum computer could get the job done

with just a few hundred atoms.

And so the brain of that computer...

it would be smaller than a grain of sand.

There's no doubt we're getting better and better

at harnessing the power at the quantum world,

and who knows where that could take us?

But we can't forget that at the heart of this theory,

which has given us so much,there is still a gaping hole.

All the weirdness down at the quantum lever--

at the scale of atoms and particles--

where does the weirdness go?

Why can things in the quantum world

hover in a state of uncertainty,

seemingly being partly here and partly there,

with so many possibilities,while you and I--,

who after all, are made of atoms and particles--

seem to always be stuck in a single definite state?

We are always either here or there.

Niels Bohr offered no real explanation

for why all the weird fuzziness of the quantum world

seems to vanish as things increase in size.

As powerful and accurate

as quantum mechanics has proven to be,

scientists are stll struggling to figure this out.

Some believe that there is some detail missing

in the equations of quantum mechanics.

And so, even though there are multiple possibilities

in the tiny world, the missing details would adjust the numbers

on our way up from atoms to objects in the big world

so that it would become clear

that all but one of those possibilities disappear,

resulting in a single,certain outcome.

Other physicists believe that all the possibilities

that exist in the quantum world,they never do go away.

Instead, each and every possible outcome actually happens,

only most of them happen

in other universes parallel to our own.

It's a mind-blowing idea,

but reality could go beyond the one universe we all see

and be constantly branching off,

creating new,alternative worlds,

where every possibility gets played out.

This is the frontier of quantum mechanics,

and no one knows where it will lead.

The very fact that our reality is much grander than we thought,

much more strange and mysterious than we thought,

is to me also very beautiful and awe-inspiring.

The beauty of science is that it allows you to learn things

which go beyond your wildest dreams.

And quantum mechanics is the epitome of that.

After you learn quantum mechanics,

you're never really the same again.

GREENE: As strange as quantum mechanics may be,

what's now clear is that there's no boundary

between the worlds of the tiny and the big.

Instead, these laws apply everywhere,

and it's just that their weird features are most apparent

when things are small.

And so the discovery of quantum mechanics

has revealed a reality,our reality,

that's both shocking and thrilling,

bringing us that much closer to fully understanding

the fabric of the cosmos.

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