Everything you need to know about the bizarre world of Quantum mechanics, the relationship between measurement and entanglement, wave particle duality, Schrodinger’s cat, EPR paradox and Bell inequality.

1. Measurement and Entanglement: Entanglement is a curious quantum phenomenon that links the properties of two or more particles in a way that the state of one particle instantly influences the state of the others, regardless of distance. Measurement plays a crucial role in entanglement, as observing the state of one particle forces it to adopt a specific value, thus determining the states of the entangled particles. This intriguing relationship raises questions about the nature of reality and the role of observers in shaping it.
   
   
2. Wave-Particle Duality: Wave-particle duality is a central concept in quantum mechanics that describes how subatomic particles exhibit both wave-like and particle-like properties. Experiments like the double-slit experiment have shown that particles can behave as waves when unobserved, creating interference patterns, but act as individual particles when directly observed. This enigmatic duality is a key aspect of quantum mechanics, challenging our intuitive understanding of matter and energy.
   
   
3. Schrödinger’s Paradoxical Cat: Schrödinger’s cat is a famous thought experiment devised by Austrian physicist Erwin Schrödinger to illustrate the bizarre implications of quantum mechanics on the macroscopic world. In this scenario, a cat is placed in a sealed box with a radioactive atom, a Geiger counter, and a vial of poison. If the atom decays, the poison is released, killing the cat. Until the box is opened and observed, the cat is considered both alive and dead simultaneously—a phenomenon known as superposition. Schrödinger’s cat demonstrates the limits of applying quantum principles to everyday objects.
   
   
4. EPR Paradox and Bell Inequality: The EPR (Einstein-Podolsky-Rosen) paradox is a thought experiment challenging the notion of quantum entanglement and its implications for the “spooky action at a distance” phenomenon. Albert Einstein, Boris Podolsky, and Nathan Rosen proposed this paradox to argue that quantum mechanics might be incomplete, suggesting that “hidden variables” could exist. However, physicist John Bell later formulated the Bell inequality, which showed that the predictions of quantum mechanics involving entanglement were correct and could not be explained by local hidden variables. This led to numerous experimental tests and further solidified the legitimacy of quantum mechanics, despite its counterintuitive nature.

Video source: Eugene Khutoryansky