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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 lightbulb is not
a more powerful candle.
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You cannot build a lightbulb
by building better and better candles.
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A lightbulb 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 lightbulb
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. 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,
non-binary identity.
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It can exist in a super-position,
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 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 super-position 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 un-mix the zero and one,
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perfectly recovering heads
so that you lose every time.
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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,
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 because it
harnessed super-position 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
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from one location to another 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)