WEBVTT

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I'm in the business
of safeguarding secrets,

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and this includes your secrets.

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Cryptographers are
the first line of defense

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in an ongoing war that's been
raging for centuries:

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a war between code makers

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and code breakers.

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And this is a war on information.

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The modern battlefield
for information is digital.

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And it wages across your phones,

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your computers

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and the internet.

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Our job is to create systems that scramble
your emails and credit card numbers,

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your phone calls and text messages --

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and that includes those saucy selfies --

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(Laughter)

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so that all of this information
can only be descrambled

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by the recipient that it's intended for.

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Now, until very recently,

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we thought we'd won this war for good.

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Right now, each of your smartphones
is using encryption

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that we thought was unbreakable
and that was going to remain that way.

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We were wrong,

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because quantum computers are coming,

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and they're going to change
the game completely.

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Throughout history,
cryptography and code-breaking

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has always been this game
of cat and mouse.

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Back in the 1500s,

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Queen Mary of the Scots thought
she was sending encrypted letters

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that only her soldiers could decipher.

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But Queen Elizabeth of England,

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she had code breakers
that were all over it.

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They decrypted Mary's letters,

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saw that she was attempting
to assassinate Elizabeth

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and, subsequently,
they chopped Mary's head off.

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A few centuries later, in World War II,

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the Nazis communicated
using the Engima code,

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a much more complicated encryption scheme
that they thought was unbreakable.

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But then good old Alan Turing,

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the same guy who invented
what we now call the modern computer,

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he built a machine and used it
to break Enigma.

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He deciphered the German messages

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and helped to bring Hitler
and his Third Reich to a halt.

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And so the story has gone
throughout the centuries.

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Cryptographers improve their encryption,

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and then code breakers fight back
and they find a way to break it.

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This war's gone back and forth,
and it's been pretty neck and neck.

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That was until the 1970s,

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when some cryptographers
made a huge breakthrough.

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They discovered an extremely
powerful way to do encryption

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called "public-key cryptography."

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Unlike all of the prior methods used
throughout history, it doesn't require

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that the two parties that want to send
each other confidential information

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have exchanged the secret key beforehand.

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The magic of public-key cryptography
is that it allows us to connect securely

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with anyone in the world,

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whether we've exchanged
data before or not,

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and to do it so fast that you and I
don't even realize it's happening.

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Whether you're texting your mate
to catch up for a beer,

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or you're a bank that's transferring
billions of dollars to another bank,

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modern encryption enables us
to send data that can be secured

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in a matter of milliseconds.

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The brilliant idea that makes
this magic possible,

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it relies on hard mathematical problems.

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Cryptographers are deeply interested
in things that calculators can't do.

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For example, calculators can multiply
any two numbers you like,

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no matter how big the size.

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But going back the other way --

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starting with the product and then asking,

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"Which two numbers multiply
to give this one?" --

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that's actually a really hard problem.

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If I asked you to find which two-digit
numbers multiply to give 851,

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even with a calculator,

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most people in this room would have
a hard time finding the answer

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by the time I'm finished with this talk.

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And if I make the numbers a little larger,

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then there's no calculator on earth
that can do this.

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In fact, even the world's
fastest supercomputer

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would take longer
than the life age of the universe

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to find the two numbers
that multiply to give this one.

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And this problem,
called "integer factorization,"

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is exactly what each of your smartphones
and laptops is using right now

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to keep your data secure.

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This is the basis of modern encryption.

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And the fact that all the computing power
on the planet combined can't solve it,

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that's the reason we cryptographers
thought we'd found a way

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to stay ahead of the code
breakers for good.

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Perhaps we got a little cocky

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because just when we thought
the war was won,

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a bunch of 20th-century physicists
came to the party,

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and they revealed
that the laws of the universe,

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the same laws that modern
cryptography was built upon,

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they aren't as we thought they were.

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We thought that one object couldn't be
in two places at the same time.

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It's not the case.

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We thought nothing can possibly spin
clockwise and anticlockwise

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simultaneously.

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But that's incorrect.

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And we thought that two objects
on opposite sides of the universe,

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light years away from each other,

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they can't possible influence
one another instantaneously.

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We were wrong again.

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And isn't that always the way
life seems to go?

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Just when you think you've got
everything covered, your ducks in a row,

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a bunch of physicists come along

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and reveal that the fundamental laws
of the universe are completely different

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to what you thought?

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(Laughter)

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And it screws everything up.

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See, in the teeny tiny subatomic realm,

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at the level of electrons and protons,

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the classical laws of physics,

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the ones that we all know and love,

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they go out the window.

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And it's here that the laws
of quantum mechanics kick in.

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In quantum mechanics,

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an electron can be spinning clockwise
and anticlockwise at the same time,

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and a proton can be in two places at once.

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It sounds like science fiction,

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but that's only because
the crazy quantum nature of our universe,

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it hides itself from us.

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And it stayed hidden from us
until the 20th century.

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But now that we've seen it,
the whole world is in an arms race

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to try to build a quantum computer --

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a computer that can harness the power
of this weird and wacky quantum behavior.

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These things are so revolutionary

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and so powerful

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that they'll make today's
fastest supercomputer

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look useless in comparison.

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In fact, for certain problems
that are of great interest to us,

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today's fastest supercomputer
is closer to an abacus

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than to a quantum computer.

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That's right, I'm talking about
those little wooden things with the beads.

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Quantum computers can simulate
chemical and biological processes

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that are far beyond the reach
of our classical computers.

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And as such, they promise to help us solve
some of our planet's biggest problems.

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They're going to help us
combat global hunger;

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to tackle climate change;

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to find cures for diseases and pandemics
for which we've so far been unsuccessful;

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to create superhuman
artificial intelligence;

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and perhaps even more important
than all of those things,

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they're going to help us understand
the very nature of our universe.

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But with this incredible potential

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comes an incredible risk.

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Remember those big numbers
I talked about earlier?

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I'm not talking about 851.

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In fact, if anyone in here
has been distracted

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trying to find those factors,

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I'm going to put you out of your misery
and tell you that it's 23 times 37.

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(Laughter)

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I'm talking about the much
bigger number that followed it.

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While today's fastest supercomputer
couldn't find those factors

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in the life age of the universe,

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a quantum computer
could easily factorize numbers

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way, way bigger than that one.

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Quantum computers will break
all of the encryption currently used

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to protect you and I from hackers.

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And they'll do it easily.

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Let me put it this way:

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if quantum computing was a spear,

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then modern encryption,

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the same unbreakable system
that's protected us for decades,

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it would be like a shield
made of tissue paper.

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Anyone with access to a quantum computer
will have the master key

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to unlock anything they like
in our digital world.

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They could steal money from banks

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and control economies.

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They could power off hospitals
or launch nukes,

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or they could just sit back
and watch all of us on our webcams

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without any of us knowing
that this is happening.

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Now, the fundamental unit of information
on all of the computers we're used to,

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like this one,

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it's called a "bit."

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A single bit can be one of two states:

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it can be a zero or it can be a one.

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When I FaceTime my mum
from the other side of the world --

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and she's going to kill
me for having this slide --

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(Laughter)

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we're actually just sending each other
long sequences of zeroes and ones

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that bounce from computer to computer,
from satellite to satellite,

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transmitting our data at a rapid pace.

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Bits are certainly very useful.

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In fact, anything
we currently do with technology

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is indebted to the usefulness of bits.

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But we're starting to realize

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that bits are really poor at simulating
complex molecules and particles.

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And this is because, in some sense,

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subatomic processes can be doing
two or more opposing things

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at the same time

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as they follow these bizarre rules
of quantum mechanics.

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So, late last century,

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some really brainy physicists
had this ingenious idea:

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to instead build computers
that are founded

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on the principles of quantum mechanics.

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Now, the fundamental unit of information
of a quantum computer,

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it's called a "qubit."

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It stands for "quantum bit."

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Instead of having just two states,
like zero or one,

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a qubit can be an infinite
number of states.

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And this corresponds to it being
some combination of both zero and one

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at the same time,

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a phenomenon that we call "superposition."

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And when we have two qubits
in superposition,

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we're actually working across
all four combinations

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of zero-zero, zero-one,
one-zero and one-one.

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With three qubits,

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we're working in superposition
across eight combinations,

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and so on.

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Each time we add a single qubit,
we double the number of combinations

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that we can work with in superposition

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at the same time.

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And so when we scale up
to work with many qubits,

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we can work with an exponential
number of combinations

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at the same time.

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And this just hints at where the power
of quantum computing is coming from.

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Now, in modern encryption,

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our secret keys, like the two factors
of that larger number,

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they're just long sequences
of zeroes and ones.

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To find them,

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a classical computer must go through
every single combination,

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one after the other,

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until it finds the one that works
and breaks our encryption.

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But on a quantum computer,

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with enough qubits in superposition,

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information can be extracted
from all combinations at the same time.

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In very few steps,

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a quantum computer can brush aside
all of the incorrect combinations,

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home in on the correct one

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and then unlock our treasured secrets.

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Now, at the crazy quantum level,

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something truly incredible
is happening here.

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The conventional wisdom
held by many leading physicists --

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and you've got to stay
with me on this one --

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is that each combination is actually
examined by its very own quantum computer

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inside its very own parallel universe.

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Each of these combinations,
they add up like waves in a pool of water.

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The combinations that are wrong,

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they cancel each other out,

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and the combinations that are right,

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they reinforce and amplify each other.

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So at the end of the quantum
computing program,

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all that's left is the correct answer,

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that we can then observe
here in this universe.

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Now, if that doesn't make
complete sense to you, don't stress.

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(Laughter)

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You're in good company.

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Niels Bohr, one of
the pioneers of this field,

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he once said that anyone
who could contemplate quantum mechanics

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without being profoundly shocked,

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they haven't understood it.

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(Laughter)

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But you get an idea
of what we're up against,

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and why it's now up to us cryptographers

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to really step it up.

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And we have to do it fast,

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because quantum computers,

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they already exist in labs
all over the world.

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Fortunately, at this minute,

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they only exist
at a relatively small scale,

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still too small to break
our much larger cryptographic keys.

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But we might not be safe for long.

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Some folks believe that secret
government agencies

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have already built a big enough one,

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and they just haven't told anyone yet.

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Some pundits say
they're more like 10 years off.

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Some people say it's more like 30.

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You might think that
if quantum computers are 10 years away,

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surely that's enough time
for us cryptographers to figure it out

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and to secure the internet in time.

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But unfortunately, it's not that easy.

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Even if we ignore
the many years that it takes

00:13:27.733 --> 00:13:31.399
to standardize and deploy and then
roll out new encryption technology,

00:13:31.423 --> 00:13:33.751
in some ways we may already be too late.

00:13:35.407 --> 00:13:38.579
Smart digital criminals
and government agencies

00:13:38.603 --> 00:13:42.882
may already be storing
our most sensitive encrypted data

00:13:42.906 --> 00:13:45.499
in anticipation for
the quantum future ahead.

00:13:47.069 --> 00:13:48.807
The messages of foreign leaders,

00:13:50.100 --> 00:13:51.455
of war generals

00:13:52.653 --> 00:13:54.815
or of individuals who question power,

00:13:55.936 --> 00:13:57.486
they're encrypted for now.

00:13:58.487 --> 00:14:00.088
But as soon as the day comes

00:14:00.112 --> 00:14:02.888
that someone gets their hands
on a quantum computer,

00:14:02.912 --> 00:14:06.038
they can retroactively break
anything from the past.

00:14:07.078 --> 00:14:09.108
In certain government
and financial sectors

00:14:09.132 --> 00:14:10.535
or in military organizations,

00:14:10.559 --> 00:14:13.633
sensitive data has got to remain
classified for 25 years.

00:14:14.273 --> 00:14:17.453
So if a quantum computer
really will exist in 10 years,

00:14:17.477 --> 00:14:19.767
then these guys are already
15 years too late

00:14:19.791 --> 00:14:21.501
to quantum-proof their encryption.

NOTE Paragraph

00:14:22.858 --> 00:14:24.834
So while many scientists around the world

00:14:24.858 --> 00:14:27.761
are racing to try to build
a quantum computer,

00:14:27.785 --> 00:14:31.235
us cryptographers are urgently
looking to reinvent encryption

00:14:31.259 --> 00:14:33.461
to protect us long before that day comes.

00:14:34.718 --> 00:14:37.692
We're looking for new,
hard mathematical problems.

00:14:38.435 --> 00:14:41.446
We're looking for problems that,
just like factorization,

00:14:41.470 --> 00:14:44.479
can be used on our smartphones
and on our laptops today.

00:14:45.596 --> 00:14:49.971
But unlike factorization,
we need these problems to be so hard

00:14:49.995 --> 00:14:52.841
that they're even unbreakable
with a quantum computer.

NOTE Paragraph

00:14:54.366 --> 00:14:57.972
In recent years, we've been digging around
a much wider realm of mathematics

00:14:57.996 --> 00:14:59.522
to look for such problems.

00:15:00.205 --> 00:15:02.176
We've been looking at numbers and objects

00:15:02.200 --> 00:15:04.368
that are far more exotic
and far more abstract

00:15:04.392 --> 00:15:06.348
than the ones that you and I are used to,

00:15:06.372 --> 00:15:07.969
like the ones on our calculators.

00:15:07.993 --> 00:15:10.373
And we believe we've found
some geometric problems

00:15:10.397 --> 00:15:11.796
that just might do the trick.

00:15:12.383 --> 00:15:15.446
Now, unlike those two-
and three-dimensional geometric problems

00:15:15.470 --> 00:15:19.169
that we used to have to try to solve
with pen and graph paper in high school,

00:15:19.193 --> 00:15:23.422
most of these problems are defined
in well over 500 dimensions.

00:15:24.453 --> 00:15:28.209
So not only are they a little hard
to depict and solve on graph paper,

00:15:28.233 --> 00:15:31.705
but we believe they're even
out of the reach of a quantum computer.

00:15:33.392 --> 00:15:35.089
So though it's early days,

00:15:35.113 --> 00:15:39.618
it's here that we are putting our hope
as we try to secure our digital world

00:15:39.642 --> 00:15:41.612
moving into its quantum future.

NOTE Paragraph

00:15:43.171 --> 00:15:45.024
Just like all of the other scientists,

00:15:45.048 --> 00:15:47.211
we cryptographers are tremendously excited

00:15:47.235 --> 00:15:51.092
at the potential of living in a world
alongside quantum computers.

00:15:52.839 --> 00:15:54.992
They could be such a force for good.

00:15:57.508 --> 00:16:01.756
But no matter what
technological future we live in,

00:16:04.867 --> 00:16:09.723
our secrets will always be
a part of our humanity.

00:16:10.637 --> 00:16:12.871
And that is worth protecting.

NOTE Paragraph

00:16:13.559 --> 00:16:14.713
Thanks.

NOTE Paragraph

00:16:14.737 --> 00:16:17.843
(Applause)