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

140,760 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,
0
15260
3000
00:18
and your brain can be broken into two parts.
1
18260
3000
00:21
There's the left half, which is the logical side,
2
21260
2000
00:23
and then the right half,
3
23260
2000
00:25
which is the intuitive.
4
25260
2000
00:27
And so if we had a scale to measure the aptitude of each hemisphere,
5
27260
3000
00:30
then we can plot our brain.
6
30260
2000
00:32
And for example, this would be somebody who's completely logical.
7
32260
3000
00:35
This would be someone who's entirely intuitive.
8
35260
3000
00:39
So where would you put your brain on this scale?
9
39260
3000
00:42
Some of us may have opted for one of these extremes,
10
42260
3000
00:45
but I think for most people in the audience,
11
45260
2000
00:47
your brain is something like this --
12
47260
2000
00:49
with a high aptitude in both hemispheres at the same time.
13
49260
3000
00:52
It's not like they're mutually exclusive or anything.
14
52260
2000
00:54
You can be logical and intuitive.
15
54260
2000
00:56
And so I consider myself one of these people,
16
56260
3000
00:59
along with most of the other experimental quantum physicists,
17
59260
3000
01:02
who need a good deal of logic
18
62260
2000
01:04
to string together these complex ideas.
19
64260
2000
01:06
But at the same time, we need a good deal of intuition
20
66260
3000
01:09
to actually make the experiments work.
21
69260
2000
01:11
How do we develop this intuition? Well we like to play with stuff.
22
71260
3000
01:14
So we go out and play with it, and then we see how it acts,
23
74260
3000
01:17
and then we develop our intuition from there.
24
77260
3000
01:20
And really you do the same thing.
25
80260
2000
01:22
So some intuition
26
82260
2000
01:24
that you may have developed over the years
27
84260
2000
01:26
is that one thing is only in one place at a time.
28
86260
4000
01:30
I mean, it can sound weird to think about
29
90260
3000
01:33
one thing being in two different places at the same time,
30
93260
4000
01:37
but you weren't born with this notion, you developed it.
31
97260
3000
01:40
And I remember watching a kid playing on a car stop.
32
100260
3000
01:43
He was just a toddler and he wasn't very good at it, and he kept falling over.
33
103260
3000
01:46
But I bet playing with this car stop taught him a really valuable lesson,
34
106260
3000
01:49
and that's that large things don't let you get right past them,
35
109260
4000
01:53
and that they stay in one place.
36
113260
3000
01:56
And so this is a great conceptual model to have of the world,
37
116260
3000
01:59
unless you're a particle physicist.
38
119260
2000
02:01
It'd be a terrible model for a particle physicist,
39
121260
2000
02:03
because they don't play with car stops,
40
123260
2000
02:05
they play with these little weird particles.
41
125260
3000
02:08
And when they play with their particles,
42
128260
2000
02:10
they find they do all sorts of really weird things --
43
130260
2000
02:12
like they can fly right through walls,
44
132260
3000
02:15
or they can be in two different places at the same time.
45
135260
4000
02:19
And so they wrote down all these observations,
46
139260
3000
02:22
and they called it the theory of quantum mechanics.
47
142260
4000
02:26
And so that's where physics was at a few years ago;
48
146260
3000
02:29
you needed quantum mechanics
49
149260
2000
02:31
to describe little, tiny particles.
50
151260
2000
02:33
But you didn't need it
51
153260
2000
02:35
to describe the large, everyday objects around us.
52
155260
4000
02:39
This didn't really sit well with my intuition,
53
159260
3000
02:42
and maybe it's just because I don't play with particles very often.
54
162260
3000
02:45
Well, I play with them sometimes,
55
165260
2000
02:47
but not very often.
56
167260
2000
02:49
And I've never seen them.
57
169260
2000
02:51
I mean, nobody's ever seen a particle.
58
171260
3000
02:54
But it didn't sit well with my logical side either.
59
174260
3000
02:57
Because if everything is made up of little particles
60
177260
3000
03:00
and all the little particles
61
180260
2000
03:02
follow quantum mechanics,
62
182260
2000
03:04
then shouldn't everything just follow quantum mechanics?
63
184260
3000
03:09
I don't see any reason why it shouldn't.
64
189260
3000
03:12
And so I'd feel a lot better about the whole thing
65
192260
2000
03:14
if we could somehow show
66
194260
2000
03:16
that an everyday object
67
196260
2000
03:18
also follows quantum mechanics.
68
198260
2000
03:20
So a few years ago, I set off to do just that.
69
200260
3000
03:23
So I made one.
70
203260
3000
03:26
This is the first object
71
206260
2000
03:28
that you can see
72
208260
2000
03:30
that has been in a mechanical quantum superposition.
73
210260
3000
03:33
So what we're looking at here
74
213260
2000
03:35
is a tiny computer chip.
75
215260
2000
03:37
And you can sort of see this green dot right in the middle.
76
217260
3000
03:40
And that's this piece of metal I'm going to be talking about in a minute.
77
220260
3000
03:43
This is a photograph of the object.
78
223260
2000
03:45
And here I'll zoom in a little bit. We're looking right there in the center.
79
225260
3000
03:48
And then here's a really, really big close-up of the little piece of metal.
80
228260
3000
03:51
So what we're looking at is a little chunk of metal,
81
231260
2000
03:53
and it's shaped like a diving board, and it's sticking out over a ledge.
82
233260
3000
03:56
And so I made this thing
83
236260
2000
03:58
in nearly the same way as you make a computer chip.
84
238260
2000
04:00
I went into a clean room with a fresh silicon wafer,
85
240260
3000
04:03
and then I just cranked away at all the big machines for about 100 hours.
86
243260
3000
04:06
For the last stuff, I had to build my own machine --
87
246260
2000
04:08
to make this swimming pool-shaped hole
88
248260
3000
04:11
underneath the device.
89
251260
2000
04:13
This device has the ability
90
253260
2000
04:15
to be in a quantum superposition,
91
255260
2000
04:17
but it needs a little help to do it.
92
257260
2000
04:19
Here, let me give you an analogy.
93
259260
2000
04:21
You know how uncomfortable it is to be in a crowded elevator?
94
261260
3000
04:24
I mean, when I'm in an elevator all alone, I do all sorts of weird things,
95
264260
3000
04:27
but then other people get on board
96
267260
2000
04:29
and I stop doing those things
97
269260
2000
04:31
because I don't want to bother them,
98
271260
2000
04:33
or, frankly, scare them.
99
273260
3000
04:36
So quantum mechanics says
100
276260
2000
04:38
that inanimate objects feel the same way.
101
278260
3000
04:41
The fellow passengers for inanimate objects
102
281260
2000
04:43
are not just people,
103
283260
2000
04:45
but it's also the light shining on it
104
285260
2000
04:47
and the wind blowing past it and the heat of the room.
105
287260
3000
04:50
And so we knew, if we wanted to see
106
290260
2000
04:52
this piece of metal behave quantum mechanically,
107
292260
3000
04:55
we're going to have to kick out all the other passengers.
108
295260
2000
04:57
And so that's what we did.
109
297260
2000
04:59
We turned off the lights,
110
299260
2000
05:01
and then we put it in a vacuum and sucked out all the air,
111
301260
2000
05:03
and then we cooled it down
112
303260
2000
05:05
to just a fraction of a degree above absolute zero.
113
305260
2000
05:07
Now, all alone in the elevator,
114
307260
2000
05:09
the little chunk of metal is free to act however it wanted.
115
309260
2000
05:11
And so we measured its motion.
116
311260
2000
05:13
We found it was moving in really weird ways.
117
313260
2000
05:15
Instead of just sitting perfectly still, it was vibrating,
118
315260
3000
05:18
and the way it was vibrating was breathing something like this --
119
318260
3000
05:21
like expanding and contracting bellows.
120
321260
2000
05:23
And by giving it a gentle nudge,
121
323260
2000
05:25
we were able to make it both vibrate
122
325260
2000
05:27
and not vibrate
123
327260
2000
05:29
at the same time --
124
329260
2000
05:31
something that's only allowed with quantum mechanics.
125
331260
3000
05:34
So what I'm telling you here is something truly fantastic.
126
334260
3000
05:37
What does it mean for one thing
127
337260
2000
05:39
to be both vibrating and not vibrating
128
339260
2000
05:41
at the same time?
129
341260
2000
05:43
So let's think about the atoms.
130
343260
2000
05:45
So in one case:
131
345260
2000
05:47
all the trillions of atoms that make up that chunk of metal
132
347260
3000
05:50
are sitting still
133
350260
2000
05:52
and at the same time those same atoms
134
352260
2000
05:54
are moving up and down.
135
354260
2000
05:56
Now it's only at precise times when they align.
136
356260
3000
05:59
The rest of the time they're delocalized.
137
359260
2000
06:01
That means that every atom
138
361260
2000
06:03
is in two different places at the same time,
139
363260
2000
06:05
which in turn means the entire chunk of metal
140
365260
3000
06:08
is in two different places.
141
368260
2000
06:10
I think this is really cool.
142
370260
2000
06:12
(Laughter)
143
372260
2000
06:14
Really.
144
374260
2000
06:16
(Applause)
145
376260
3000
06:19
It was worth locking myself in a clean room to do this for all those years
146
379260
5000
06:24
because, check this out,
147
384260
2000
06:26
the difference in scale
148
386260
2000
06:28
between a single atom and that chunk of metal
149
388260
2000
06:30
is about the same as the difference
150
390260
2000
06:32
between that chunk of metal and you.
151
392260
2000
06:34
So if a single atom can be in two different places at the same time,
152
394260
3000
06:37
that chunk of metal can be in two different places,
153
397260
3000
06:40
then why not you?
154
400260
2000
06:42
I mean, this is just my logical side talking.
155
402260
3000
06:46
So imagine if you're in multiple places at the same time,
156
406260
4000
06:50
what would that be like?
157
410260
3000
06:53
How would your consciousness
158
413260
2000
06:55
handle your body being delocalized in space?
159
415260
4000
06:59
There's one more part to the story.
160
419260
2000
07:01
It's when we warmed it up,
161
421260
2000
07:03
and we turned on the lights and looked inside the box,
162
423260
3000
07:06
we saw that the piece metal was still there in one piece.
163
426260
4000
07:10
And so I had to develop this new intuition,
164
430260
3000
07:13
that it seems like all the objects in the elevator
165
433260
3000
07:16
are really just quantum objects
166
436260
2000
07:18
just crammed into a tiny space.
167
438260
2000
07:20
You hear a lot of talk
168
440260
2000
07:22
about how quantum mechanics says that everything is all interconnected.
169
442260
3000
07:25
Well, that's not quite right.
170
445260
2000
07:27
It's more than that; it's deeper.
171
447260
3000
07:30
It's that those connections,
172
450260
2000
07:32
your connections to all the things around you,
173
452260
3000
07:35
literally define who you are,
174
455260
3000
07:38
and that's the profound weirdness of quantum mechanics.
175
458260
3000
07:41
Thank you.
176
461260
2000
07:43
(Applause)
177
463260
2000
About this website

This site will introduce you to YouTube videos that are useful for learning English. You will see English lessons taught by top-notch teachers from around the world. Double-click on the English subtitles displayed on each video page to play the video from there. The subtitles scroll in sync with the video playback. If you have any comments or requests, please contact us using this contact form.

https://forms.gle/WvT1wiN1qDtmnspy7