Aaron O'Connell: Making sense of a visible quantum object

140,634 views ・ 2011-06-03

TED


Please double-click on the English subtitles below to play the video.

00:15
This is a representation of your brain,
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and your brain can be broken into two parts.
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There's the left half, which is the logical side,
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and then the right half,
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which is the intuitive.
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And so if we had a scale to measure the aptitude of each hemisphere,
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then we can plot our brain.
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And for example, this would be somebody who's completely logical.
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This would be someone who's entirely intuitive.
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So where would you put your brain on this scale?
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Some of us may have opted for one of these extremes,
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but I think for most people in the audience,
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your brain is something like this --
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with a high aptitude in both hemispheres at the same time.
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00:52
It's not like they're mutually exclusive or anything.
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You can be logical and intuitive.
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And so I consider myself one of these people,
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along with most of the other experimental quantum physicists,
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who need a good deal of logic
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to string together these complex ideas.
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But at the same time, we need a good deal of intuition
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01:09
to actually make the experiments work.
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01:11
How do we develop this intuition? Well we like to play with stuff.
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01:14
So we go out and play with it, and then we see how it acts,
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and then we develop our intuition from there.
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01:20
And really you do the same thing.
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01:22
So some intuition
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that you may have developed over the years
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is that one thing is only in one place at a time.
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I mean, it can sound weird to think about
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one thing being in two different places at the same time,
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but you weren't born with this notion, you developed it.
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And I remember watching a kid playing on a car stop.
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He was just a toddler and he wasn't very good at it, and he kept falling over.
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But I bet playing with this car stop taught him a really valuable lesson,
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and that's that large things don't let you get right past them,
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and that they stay in one place.
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And so this is a great conceptual model to have of the world,
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unless you're a particle physicist.
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It'd be a terrible model for a particle physicist,
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because they don't play with car stops,
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they play with these little weird particles.
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And when they play with their particles,
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they find they do all sorts of really weird things --
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like they can fly right through walls,
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or they can be in two different places at the same time.
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And so they wrote down all these observations,
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and they called it the theory of quantum mechanics.
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And so that's where physics was at a few years ago;
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you needed quantum mechanics
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to describe little, tiny particles.
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But you didn't need it
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to describe the large, everyday objects around us.
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This didn't really sit well with my intuition,
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and maybe it's just because I don't play with particles very often.
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Well, I play with them sometimes,
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but not very often.
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And I've never seen them.
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I mean, nobody's ever seen a particle.
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But it didn't sit well with my logical side either.
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Because if everything is made up of little particles
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and all the little particles
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follow quantum mechanics,
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then shouldn't everything just follow quantum mechanics?
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I don't see any reason why it shouldn't.
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And so I'd feel a lot better about the whole thing
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if we could somehow show
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that an everyday object
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also follows quantum mechanics.
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So a few years ago, I set off to do just that.
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So I made one.
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This is the first object
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that you can see
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that has been in a mechanical quantum superposition.
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So what we're looking at here
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is a tiny computer chip.
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And you can sort of see this green dot right in the middle.
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And that's this piece of metal I'm going to be talking about in a minute.
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This is a photograph of the object.
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And here I'll zoom in a little bit. We're looking right there in the center.
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And then here's a really, really big close-up of the little piece of metal.
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So what we're looking at is a little chunk of metal,
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and it's shaped like a diving board, and it's sticking out over a ledge.
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And so I made this thing
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in nearly the same way as you make a computer chip.
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I went into a clean room with a fresh silicon wafer,
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and then I just cranked away at all the big machines for about 100 hours.
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For the last stuff, I had to build my own machine --
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to make this swimming pool-shaped hole
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underneath the device.
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This device has the ability
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to be in a quantum superposition,
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but it needs a little help to do it.
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04:19
Here, let me give you an analogy.
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You know how uncomfortable it is to be in a crowded elevator?
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I mean, when I'm in an elevator all alone, I do all sorts of weird things,
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but then other people get on board
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and I stop doing those things
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because I don't want to bother them,
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or, frankly, scare them.
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So quantum mechanics says
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that inanimate objects feel the same way.
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The fellow passengers for inanimate objects
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are not just people,
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but it's also the light shining on it
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and the wind blowing past it and the heat of the room.
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04:50
And so we knew, if we wanted to see
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this piece of metal behave quantum mechanically,
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we're going to have to kick out all the other passengers.
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And so that's what we did.
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We turned off the lights,
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05:01
and then we put it in a vacuum and sucked out all the air,
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and then we cooled it down
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to just a fraction of a degree above absolute zero.
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Now, all alone in the elevator,
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the little chunk of metal is free to act however it wanted.
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And so we measured its motion.
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We found it was moving in really weird ways.
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05:15
Instead of just sitting perfectly still, it was vibrating,
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and the way it was vibrating was breathing something like this --
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like expanding and contracting bellows.
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And by giving it a gentle nudge,
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we were able to make it both vibrate
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and not vibrate
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at the same time --
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something that's only allowed with quantum mechanics.
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05:34
So what I'm telling you here is something truly fantastic.
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05:37
What does it mean for one thing
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to be both vibrating and not vibrating
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at the same time?
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So let's think about the atoms.
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So in one case:
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all the trillions of atoms that make up that chunk of metal
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are sitting still
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and at the same time those same atoms
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are moving up and down.
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Now it's only at precise times when they align.
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The rest of the time they're delocalized.
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That means that every atom
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is in two different places at the same time,
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which in turn means the entire chunk of metal
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is in two different places.
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I think this is really cool.
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(Laughter)
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Really.
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06:16
(Applause)
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It was worth locking myself in a clean room to do this for all those years
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because, check this out,
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the difference in scale
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between a single atom and that chunk of metal
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is about the same as the difference
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between that chunk of metal and you.
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So if a single atom can be in two different places at the same time,
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that chunk of metal can be in two different places,
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then why not you?
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I mean, this is just my logical side talking.
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So imagine if you're in multiple places at the same time,
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what would that be like?
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How would your consciousness
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handle your body being delocalized in space?
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There's one more part to the story.
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It's when we warmed it up,
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and we turned on the lights and looked inside the box,
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we saw that the piece metal was still there in one piece.
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And so I had to develop this new intuition,
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that it seems like all the objects in the elevator
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are really just quantum objects
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just crammed into a tiny space.
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You hear a lot of talk
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about how quantum mechanics says that everything is all interconnected.
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Well, that's not quite right.
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It's more than that; it's deeper.
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It's that those connections,
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your connections to all the things around you,
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literally define who you are,
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and that's the profound weirdness of quantum mechanics.
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Thank you.
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07:43
(Applause)
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