Welcome to the Wacky World of Quantum!

Imagine you’re sitting on your bedroom floor after school, surrounded by your favorite things: a scuffed baseball that’s seen three seasons of little league practice, a glow-in-the-dark fidget spinner that spins for 2 whole minutes, a half-melted pack of sour gummy worms you stashed in your desk drawer, and a chipped ceramic mug that says “World’s Okayest Lego Builder” on it. You toss the baseball up in the air, and it arcs perfectly into your glove. You flip the light switch on your desk, and the little LED lamp lights up bright lemon yellow. You unwrap a gummy worm, and it’s definitely sour, definitely cherry red, and definitely in your hand, not under your bed or in the kitchen cupboard where your mom keeps the chocolate chip cookies. All of these things follow the rules you’ve learned your whole life, right? Objects are where you see them, they’re only one thing at a time, and they don’t change unless you do something to them.

But what if I told you there’s a whole other world where none of those rules apply? A world where tiny little things can be in two places at once, act like both a solid bouncy ball and a ripple in a pond at the same time, and stay in two different states until you actually look at them? That world is the quantum world, and it’s the secret magic that powers all the coolest tech you use every day, from your tablet to the WiFi that lets you watch cat videos. Welcome to your first Quantum Magic Class!

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The Rules You Already Know: Regular Playground Rules

Let’s start with the rules you’re already an expert at, because you’ve been following them since you were a baby. Scientists call these the rules of the *macroscopic world* (say that out loud: *mac-ro-sco-pic* — it just means “big enough for you to see and touch without a special microscope”). We’re going to call them the Regular Playground Rules, because they’re the rules everyone agrees to follow when you’re on the playground, at school, or at home.

Rule 1: Things are only in one place at a time

Think about your baseball. If you leave it on your desk, it’s not also under your bed, or in the kitchen, or at your friend’s house. It’s exactly where you left it. If you throw it to your friend, it’s moving through the air, but at every single tiny split-second, it’s in one exact spot — it’s just moving so fast your eyes can’t track it. It never, ever splits into two copies that fly to two different places at the same time. The same goes for your fidget spinner, your gummy worms, your Lego bricks, your pet hamster Nugget (who is definitely not in two places at once, no matter how much he wiggles when you try to pick him up), and even you! You’re only in one spot right now, sitting (or standing, or lying on the floor) reading this book.

Rule 2: Things are only one thing at a time

Your desk lamp is either on, or it’s off. There’s no such thing as a lamp that’s “half on and half off” at the same time — unless it’s broken, and then it just flickers between on and off so fast it looks blurry, but it’s still only one state at a time. Your gummy worm is either cherry or sour (okay, it’s both, but you know what I mean — it can’t be a gummy worm *and* a potato chip at the same time). Your Minecraft skin is either a creeper or a fox, not both at once (unless you use a mod, but that’s cheating!). Even Nugget the hamster is either eating a sunflower seed or napping in his little house, not doing both at the exact same time.

Rule 3: Things stay the same unless you do something to them

If you leave your baseball on the desk, it will still be a baseball when you come back 10 minutes later. It won’t turn into a rubber duck, or a slice of pizza, or a tiny quantum particle. If you leave your lamp off, it will stay off until you flip the switch. If you leave Nugget in his cage, he won’t teleport to the living room couch (well, most of the time. Hamsters are good at escaping, but that’s not quantum, that’s just Nugget being a troublemaker).

These rules are so obvious to you that you probably never even think about them. They’re the rules of the world you live in, the world of things you can see and touch. But here’s the secret: these rules only work for big things. For tiny, tiny things that are too small for even the best microscope to see, the rules are completely different.

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The Weird, Wonderful Rules of the Quantum World

All the things you see around you — your baseball, your lamp, your gummy worms, even Nugget the hamster — are made of tiny, tiny building blocks. Scientists call these building blocks *particles*, and they’re so small that if you blew up a single grain of sand to the size of the Earth, the particles inside it would be the size of oranges. These tiny particles don’t follow the Regular Playground Rules. They follow the Magic Playground Rules, and they are *weird*.

Let’s meet our first quantum particle: let’s call it a *quantum marble*, to make it easy to imagine. It’s so small you can’t see it, even with a magnifying glass, but it’s real, and it makes up everything in the universe.

Magic Rule 1: A quantum marble can be in two (or more!) places at the same time

Remember how your baseball can only be in one spot at a time? Not the quantum marble! If you put a quantum marble in a box on your desk, and then close the box and shake it, when you open the box again, the marble might be in the box… or it might be in your pocket… or it might be *in both places at the exact same time*.

Wait, what? How can something be in two places at once? It sounds like magic, but it’s real! Scientists have done hundreds of experiments to prove it. When no one is looking at the quantum marble (we call this “not measuring it”), it doesn’t pick one spot. It stays in a special state called a *superposition* (say: *soo-per-po-si-tion*), where it’s in all the possible spots at the same time. The second you look at it, or touch the box, or do anything to find out where it is, it immediately “chooses” one spot to be in. It’s like if you closed your eyes and spun around on the playground, and when you opened your eyes, you were both on the slide and the swing at the same time — but the second you looked, you picked one to sit on.

Magic Rule 2: A quantum marble can be two different things at the same time

Remember how your lamp can only be on or off? Not the quantum marble! It can act like a tiny solid ball (like a regular marble) *and* like a ripple in a pond (like a wave) at the exact same time.

Wait, how can something be a ball and a wave at the same time? Think about bubbles. When you blow a bubble, it’s a round, solid ball that floats through the air — that’s its “particle” side. But the rainbow colors on the bubble’s skin are made of light waves that bounce off the bubble’s surface — that’s its “wave” side. The bubble has both properties at once, right? Quantum marbles are like that, but even weirder: they don’t just have both properties sometimes. They *are* both a solid particle and a wave at the exact same time, until you look at them. When you look, they “pick” one side to show you.

Scientists call this *wave-particle duality* (say: *wayv-par-ti-kle dyoo-al-i-tee*), but we’re just going to call it the “two-in-one trick” for now. Light does this trick too! The tiny little bits of light are called *photons* (say: *foo-tons*), and they can be both a tiny ball of light and a wave at the same time. That’s why you can make laser pointers that make a straight line of light (the particle side) and also make light bend around corners (the wave side).

Magic Rule 3: Two quantum marbles can be “best friends” forever

This is the coolest magic rule of all. If you take two quantum marbles, shake them together for a little bit, and then pull them apart — even if you take one to your room and one to the kitchen, or one to your school and one to the moon — they become “quantum best friends.” Whatever happens to one, the other one feels *instantly*, faster than the speed