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Let's play a game.

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Imagine that you are in Las Vegas,

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in a casino,

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and you decide to play a game
on one of the casino's computers,

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just like you might play
solitaire or chess.

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The computer can make moves
in the game, just like a human player.

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This is a coin game.

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It starts with a coin showing heads,

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and the computer will play first.

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It can choose to flip the coin or not,

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but you don't get to see the outcome.

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Next, it's your turn.

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You can also choose
to flip the coin or not,

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and your move will not be revealed
to your opponent, the computer.

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Finally, the computer plays again,
and can flip the coin or not,

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and after these three rounds,

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the coin is revealed,

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and if it is heads, the computer wins,

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if it's tails, you win.

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So it's a pretty simple game,

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and if everybody plays honestly,
and the coin is fair,

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then you have a 50 percent chance
of winning this game.

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And to confirm that,

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I asked my students to play
this game on our computers,

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and after many, many tries,

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their winning rate ended up
being 50 percent, or close to 50 percent,

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as expected.

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Sounds like a boring game, right?

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But what if you could play this game
on a quantum computer?

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Now, Las Vegas casinos
do not have quantum computers,

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as far as I know,

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but IBM has built
a working quantum computer.

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Here it is.

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But what is a quantum computer?

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Well, quantum physics describes

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the behavior of atoms
and fundamental particles,

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like electrons and photons.

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So a quantum computer operates

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by controlling the behavior
of these particles,

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but in a way that is completely different
from our regular computers.

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So a quantum computer
is not just a more powerful version

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of our current computers,

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just like a light bulb
is not a more powerful candle.

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You cannot build a light bulb
by building better and better candles.

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A light bulb is a different technology,

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based on deeper scientific understanding.

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Similarly, a quantum computer
is a new kind of device,

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based on the science of quantum physics,

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and just like a light bulb
transformed society,

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quantum computers
have the potential to impact

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so many aspects of our lives,

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including our security needs,
our health care and even the internet.

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So companies all around the world
are working to build these devices,

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and to see what
the excitement is all about,

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let's play our game on a quantum computer.

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So I can log into IBM's
quantum computer from right here,

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which means I can play the game remotely,

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and so can you.

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To make this happen, you may remember
getting an email ahead of time, from TED,

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asking you whether you would choose
to flip the coin or not,

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if you played the game.

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Well, actually, we asked you to choose
between a circle or a square.

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You didn't know it, but your choice
of circle meant "flip the coin,"

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and your choice of square
was "don't flip."

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We received 372 responses.

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Thank you.

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That means we can play 372 games
against the quantum computer

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using your choices.

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And it's a pretty fast game to play,

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so I can show you the results right here.

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Unfortunately, you didn't do very well.

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(Laughter)

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The quantum computer won
almost every game.

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It lost a few only because
of operational errors in the computer.

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(Laughter)

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So how did it achieve
this amazing winning streak?

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It seems like magic or cheating,

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but actually, it's just
quantum physics in action.

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Here's how it works.

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A regular computer simulates
heads or tails of a coin as a bit,

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a zero or a one,

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or a current flipping on and off
inside your computer chip.

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A quantum computer
is completely different.

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A quantum bit has a more fluid,
nonbinary identity.

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It can exist in a superposition,
or a combination of zero and one,

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with some probability of being zero
and some probability of being one.

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In other words,
its identity is on a spectrum.

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For example, it could have
a 70 percent chance of being zero

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and a 30 percent chance of being one

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or 80-20 or 60-40.

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The possibilities are endless.

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The key idea here

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is that we have to give up
on precise values of zero and one

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and allow for some uncertainty.

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So during the game,

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the quantum computer creates
this fluid combination of heads and tails,

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zero and one,

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so that no matter what the player does,

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flip or no flip,

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the superposition remains intact.

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It's kind of like stirring
a mixture of two fluids.

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Whether or not you stir,
the fluids remain in a mixture,

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but in its final move,

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the quantum computer
can unmix the zero and one,

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perfectly recovering heads
so that you lose every time.

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(Laughter)

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If you think this is all a bit weird,
you are absolutely right.

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Regular coins do not exist
in combinations of heads and tails.

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We do not experience
this fluid quantum reality

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in our everyday lives.

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So if you are confused by quantum,

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don't worry, you're getting it.

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(Laughter)

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But even though we don't experience
quantum strangeness,

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we can see its very real
effects in action.

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You've seen the data for yourself.

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The quantum computer won

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because it harnessed
superposition and uncertainty,

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and these quantum properties are powerful,

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not just to win coin games,

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but also to build
future quantum technologies.

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So let me give you three examples
of potential applications

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that could change our lives.

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First of all, quantum uncertainty
could be used to create private keys

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for encrypting messages
sent from one location to another

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so that hackers could not
secretly copy the key perfectly,

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because of quantum uncertainty.

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They would have to break
the laws of quantum physics

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to hack the key.

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So this kind of unbreakable encryption
is already being tested by banks

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and other institutions worldwide.

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Today, we use more than 17 billion
connected devices globally.

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Just imagine the impact quantum encryption
could have in the future.

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Secondly, quantum technologies could also
transform health care and medicine.

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For example, the design and analysis
of molecules for drug development

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is a challenging problem today,

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and that's because
exactly describing and calculating

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all of the quantum properties
of all the atoms in the molecule

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is a computationally difficult task,
even for our supercomputers.

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But a quantum computer could do better,

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because it operates using
the same quantum properties

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as the molecule it's trying to simulate.

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So future large-scale quantum
simulations for drug development

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could perhaps lead to treatments
for diseases like Alzheimer's,

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which affects thousands of lives.

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And thirdly, my favorite
quantum application

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is teleportation of information
from one location to another

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without physically transmitting
the information.

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Sounds like sci-fi, but it is possible,

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because these fluid identities
of the quantum particles

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can get entangled across space and time

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in such a way that when you change
something about one particle,

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it can impact the other,

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and that creates
a channel for teleportation.

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It's already been demonstrated
in research labs

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and could be part
of a future quantum internet.

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We don't have such a network as yet,

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but my team is working
on these possibilities,

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by simulating a quantum network
on a quantum computer.

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So we have designed and implemented
some interesting new protocols

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such as teleportation
among different users in the network

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and efficient data transmission

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and even secure voting.

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So it's a lot of fun for me,
being a quantum physicist.

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I highly recommend it.

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(Laughter)

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We get to be explorers
in a quantum wonderland.

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Who knows what applications
we will discover next.

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We must tread carefully and responsibly

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as we build our quantum future.

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And for me, personally,

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I don't see quantum physics as a tool
just to build quantum computers.

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I see quantum computers as a way
for us to probe the mysteries of nature

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and reveal more about this hidden world
outside of our experiences.

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How amazing that we humans,

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with our relatively limited
access to the universe,

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can still see far beyond our horizons

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just using our imagination
and our ingenuity.

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And the universe rewards us

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by showing us how incredibly
interesting and surprising it is.

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The future is fundamentally uncertain,

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and to me, that is certainly exciting.

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Thank you.

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(Applause)