My husband is watching YouTube and there’s a man discussing quantum entanglement.
His description: There are two particles. They can be either green or red, but they are both colors until they’re measured. Once you measure one, though, it automatically determines that the other is the same. No matter how many times you measured, or how far you separated the particles, the two would always be the same color.
Why does one being one color guarantee that the other one would be? How do they “know” to always be that color? And what sort of implication does that have for science/real world, other than being really cool?
In: Physics
Conceptually quantum entanglement is fairly simple and a lot of the “weirdness” comes from a lack of understanding of what is going on.
Imagine you have 2 boxes that each weigh one pound. You know that one of the boxes contains 1/2 a pound of feathers and 1/2 a pound of corn. The other box contains 1/2 of a pound of lead and 1/2 of a pound of stone. You are handed those boxes but are not told what is in either box.
From your perspective, both the boxes and everything in them are now entangled. Before you open a box, both boxes could contain either feathers and corn or lead and stone. Because you have no way of determining which box is which without opening them, both boxes are “mystery boxes” to you before you open them.
You now open one of the boxes and see a layer of feathers in it. Both boxes instantly stop being mystery boxes. The box you opened is the feather/corn box and the box you didn’t open is the lead/stone box – and this is true regardless of where the boxes are in the universe.
This isn’t a particularly meaningful concept in your everyday life. Its meaning comes from the fact that there are certain ways that you can interact with those boxes that will reveal what IS NOT inside without revealing what is actually inside of the box. For example, lets say you had 100 boxes and 1 of them contained drugs. You could walk a drug dog around some of the boxes and, if the drug dog didn’t signal, then you would know that drugs were not inside of those boxes. Despite the drug dog sniffing the boxes, all 100 of those boxes remain “mystery boxes” to you, but you have gained a lot of information about the boxes that the dog sniffed. IE, the boxes remain entangled despite you having extracted information about their contents.
Conceptually, being able to tell what IS NOT inside the box is useful in certain mathematical functions. For example, computers operate by telling you what something IS. This is good for most general computing tasks, but is terrible for trying to break cryptography. Quantum computers can use entanglement’s ability to tell you what something IS NOT to easily break cryptographic functions by asking simple questions like “is the decoded number bigger than 100?”
If the answer that comes back is no, then you’ve narrowed your range of possible answers as to what the thing is from infinity (which will take your normal computer trillions of years to solve) to 100 (which can be solved in a fraction of a second).
Outside of that, there are some philosophical implications of entanglement if you believe that the entangled particles truly don’t take on a definite form until they unentangle. That being said, that philosophical interpretation of both quantum theory and quantum entanglement isn’t necessary for either to work.
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