docs(notes): update quantum mechanics notes

Author: lzwjava

notes/2025-05-25-quantum-mechanics-en.md

@@ -11,4 +11,16 @@ Quantum mechanics isn't nonsense, but it can feel that way because it defies our
 
 The math—Schrödinger’s equation, Heisenberg’s uncertainty principle—predicts outcomes with stunning accuracy, underpinning tech like transistors and lasers. Critics, including Einstein, found it philosophically unsettling ("spooky action at a distance"), but no experiment has disproved it. Alternative theories, like Bohmian mechanics, exist but lack the same empirical support.
 
-That said, interpretations (e.g., Copenhagen, Many Worlds) are debated, and we don’t fully grasp *why* it works this way. It’s not nonsense; it’s just a domain where human intuition struggles, and science hasn’t fully cracked the "meaning" behind the math. If you want to dig deeper into a specific aspect, like wave-particle duality or quantum computing, let me know.
+That said, interpretations (e.g., Copenhagen, Many Worlds) are debated, and we don’t fully grasp *why* it works this way. It’s not nonsense; it’s just a domain where human intuition struggles, and science hasn’t fully cracked the "meaning" behind the math. If you want to dig deeper into a specific aspect, like wave-particle duality or quantum computing, let me know.
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+Quantum mechanics is about how the universe works at its smallest scales—think atoms, electrons, photons, and smaller. It’s a branch of physics that describes how particles, energy, and forces behave in ways that often seem bizarre compared to everyday life. Here’s the core of it:
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+- **Wave-Particle Duality**: Particles like electrons can act like both particles and waves, depending on how you observe them. The double-slit experiment shows this: electrons fired at a barrier create wave-like interference patterns.
+- **Superposition**: Particles exist in multiple states at once until measured. Schrödinger’s cat (a thought experiment) illustrates this: a cat in a box could be "both alive and dead" until you check.
+- **Entanglement**: Particles can become linked so that the state of one instantly affects the other, no matter how far apart. Einstein called this “spooky action at a distance.”
+- **Uncertainty Principle**: You can’t know everything about a particle at once—like its position and momentum—with perfect precision. The more you know about one, the less you know about the other.
+- **Probability Rules**: Quantum mechanics predicts outcomes as probabilities, not certainties. Schrödinger’s equation gives the math to calculate these probabilities.
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+It’s the foundation for modern tech like semiconductors, MRI machines, and quantum computers. But it’s also mind-bending because it challenges our sense of reality—things don’t exist in definite states until observed, and cause-and-effect gets fuzzy. Different interpretations (like Copenhagen or Many Worlds) try to explain what’s “really” happening, but none are proven. If you want a specific angle, like how it’s used in tech or a particular experiment, I can zoom in.