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

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This is a representation of your brain, and your brain can be broken into two parts. There's the left half, which is the logical side, and then the right half, which is the intuitive. So, if we add a scale to measure the aptitude of each hemisphere, then we can plot our brain. For example, this would be somebody who's completely logical; this would be someone who's entirely intuitive. So, where would you put your brain on this scale?

Some of us may have opted for, you know, one of these extremes, but I think for most people in the audience, your brain is something like this, with a high aptitude in both hemispheres at the same time. I mean, it's not like they're mutually exclusive or anything. You can be logical and intuitive. I consider myself one of these people, along with most of the other experimental quantum physicists. We need a good deal of logic to string together these complex ideas, but at the same time, we need a good deal of intuition to actually make the experiments work.

How do we develop this intuition? Well, we like to play with stuff. So, we go out and play with it, and then we see how it acts, and then we develop our intuition from there. You know, really, you do the same thing. Some intuition that you may have developed over the years is that one thing is only in one place at a time. I mean, I even sound weird to think about one thing being in two different places at the same time, but you weren't born with this notion; you developed it.

I remember watching a kid playing on a car stop. He was just a toddler, and he wasn't very good at it. He kept falling over, but I bet playing with this car stop taught him a really valuable lesson—that large things don't let you get right past them and that they stay in one place. This is a great conceptual model to have of the world. Unless you're a particle physicist, it'd be a terrible model for a particle physicist because, well, they don't play with car stops; they play with these little, weird particles.

When they play with their particles, they finally do all sorts of really weird, weird things. Like, they can fly right through walls, or they can be in two different places at the same time. So, they wrote down all these observations, and they called it the theory of quantum mechanics. And so, you know, that's where physics was at a few years ago. You needed quantum mechanics to describe little tiny particles, but you didn't need it to describe the large everyday objects around us.

This didn't really sit well with my intuition, and maybe it's just because I don't play with particles very often. Well, I mean, I play with them sometimes, but not very often. I've never seen them—I mean, nobody's ever seen a particle—but this didn't sit well with my logical side either. Because if everything is made up of little, little particles, and all the little particles follow quantum mechanics, then shouldn't everything just follow quantum mechanics?

Yeah, I don't see any reason why it shouldn't. I’d feel a lot better about the whole thing if we could somehow show that an everyday object also follows quantum mechanics. So, a few years ago, I set off to do just that. So, I made one. This is the first object that you can see that has been in a quantum superposition.

What we're looking at here is a tiny computer chip, and you can sort of see this green dot right in the middle, and that's this piece of metal I'm going to be talking about in a minute. This is a photograph of the object, and here I’m zooming in a little bit; we're looking right there in the center. Then, here's a really, really big closeup of the little piece of metal.

So, what we're looking at is a little chunk of metal, and it's shaped like a diving board and sticking out over a ledge. I made this thing in nearly the same way as you make a computer chip. I went into a clean room with a fresh silicon wafer, and then I just cranked away at all the big machines for about 100 hours. For the last step, I had to build my own machine to make this swimming pool-shaped hole underneath the device.

This device has the ability to be in a quantum superposition, but it needs a little help to do it. Here, let me give you an analogy: you know how comfortable it is to be in a crowded elevator? I mean, when I'm in an elevator, I like to do all sorts of weird things, but then other people get on board, and I stop doing those things because I don't want to bother them or, frankly, scare them.

So, quantum mechanics says that inanimate objects feel the same way. The fellow passengers for inanimate objects are not just people; it's also the light shining on it and the wind blowing past it and the heat of the room. So, we knew if we wanted to see this piece of metal behave quantum mechanically, we were going to have to kick out all the other passengers. So, that's what we did. We turned the lights off, and then we put it in a vacuum and sucked out all the air. Then, we cooled it down to just a fraction of a degree above absolute zero.

Now, all alone in the elevator, the little chunk of metal was free to act however it wanted. We measured its motion and found it was moving in really weird ways. Instead of just sitting perfectly still, it was vibrating. The way it was vibrating was something like this: like expanding and contracting bellows. By giving it a gentle nudge, we were able to make it both vibrate and not vibrate at the same time, something that's only allowed with quantum mechanics.

So, what I'm telling you here is something truly fantastic. What does it mean for one thing to be both vibrating and not vibrating at the same time? So, let's think about the atoms. In one case, all the trillions of atoms that make up that chunk of metal are just sitting still, and at the same time, those same atoms are moving up and down.

Now, it's only at precise times when they align. The rest of the time, they're delocalized. That means that every atom is in two different places at the same time, which in turn means the entire chunk of metal is in two different places. I think this is really cool—it was worth locking myself in a clean room to do this for all those years.

Um, 'cause check this out: the difference in scale between a single atom and that chunk of metal is about the same as the difference between that chunk of metal and you. So, if a single atom can be in two different places at the same time, that chunk of metal can be in two different places. Then, why not you? I mean, this is just my logical side talking. So, imagine if you were in multiple places at the same time. What would that be like? How would your consciousness handle your body being delocalized in space?

There's one more part to the story. When we warmed it up and we turned on the lights and looked inside the box, we saw that the piece of metal was still there in one piece. So, you know, I had to develop this new intuition—that it seems like all the objects in the elevator are really just quantum objects just crammed into a tiny space.

You hear a lot of talk about how quantum mechanics says that everything is all interconnected. Well, that's not quite right. It's actually more than that, and it's deeper. It's that those connections—your connections to all the things around you—literally define who you are. And that's the profound weirdness of quantum mechanics.

Thank you.

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