黃昱銘 ｜特約編輯 (臺灣大學化學系碩士)

(0:00-0:13)
So I was watching my brother play this video game, and he used a cheat code that let his character do a walk through walls hack. He pushed himself against a barrier in the game, hit some buttons and boom his character appeared on the other side.

(0:14-1:10)
Imagine if he could walk through walls in real life and it turns out. You can at a quantum level. We’re talking on a scale of the stuff that make up atoms, strange things happen at a quantum level. For one thing, all subatomic particles they’ve got split personalities, one personality is a wave and the other one’s a particle, but there’s still one being. When you want to know where they are, they seem like a particle, and when you want to know what they’re doing, they behave like waves, but you can’t ask both personalities at the same time. Basically they’ve got some serious commitment issues, and that means we can only guess where they might be. Imagine an electron has two dice six sides each, what the electron rolls is where it will sit along the line, our electron can’t commit to a position until the dice are rolled. Remember here’s commitment issues, so as our electron is shaking the dice, it’s everywhere at once. Something like us trying to measure its position has to force the electron to let go of the dice, and pick a spot of all combinations getting a 7 is more likely than 2 or 12. In reality, though the electron can be in more than just 10 spots since there are many more combinations than just two dice.

(1:11-2:11)
Now we can pick your sub-atomic particles as this a probability wave. This wave will tell us the odds of finding a particle at that location, say this is our electron’s probability wave, the peals of the wave is where we’re most likely to find the electron, and in the valley’s it’s less likely we find it there. Let’s say the electron is heading towards a barrier, as it hits the barrier the wave bounces off, but let me tell you something about waves, they are not perfect, for example, a beam of light doesn’t perfectly reflect off the surface, a small fraction of light can get through, waves won’t bounce off perfectly, so neither will the electron wave. Sometimes the wave can slip through the barrier when the wave is in the barrier, the chance of finding an electron there goes down by a lot, but if the barrier is thin enough the wave can reach the other side before it dies off, so what does that mean? Remember the wave tells us how likely it is to find the electron there. This means there’s a chance we can find our electron on the other side of the barrier or in there too. Once it’s on the other side, we can say the electron tunneled through the barrier, this is quantum tunneling, and that’s how subatomic particles can walk through walls.

(2:12-2:59)
Okay, so little elementary particles can walk through walls but I can’t, because my body’s made up of more than a quadrillion of these quantum objects, and the odds of all of them tunneling through the wall is practically impossible, so why does quantum tunneling even matter? It’s the reason we’re alive. Quantum tunneling allows nuclear fusion, sounds familiar? That’s how our sun releases huge amounts of energy that makes life on our planet possible. So how can you quantum tunnel at home, you already are! It’s one of the ways our DNA mutates among other rules that quantum physics plays in our biology. Quantum physics make it seem like the world is playing cheat codes on us, but it isn’t. It’s how the universe works. Maybe the quantum world is telling us that when faced with an obstacle there’s a small chance we can defy expectations and reach barriers.