What are "Bell Inequality" "Quantum Mechanics" and "Quantum Entanglement"?. Why have these terms been in news recently?.
Quantum mechanics is a subfield of physics that describes the behavior of particles — atoms, electrons, photons and almost everything in the molecular and sub molecular realm.
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- One important difference in the behaviour of quantum systems, when compared to classical rigid bodies, is the concept of entanglement.
Quantum entanglement is a phenomenon by which a pair of subatomic particles are allowed to exist in a shared state where they have complementary properties, such that by measuring the properties of one particle, one can automatically know the properties of the other particle.
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- This is true regardless of how far apart the two particles are transported.
- Quantum entanglement wasfirst elucidated by Erwin Schrödinger in 1935, leading to his well-known cat paradox.
Bell Inequality
- In the 1960s,John Stewart Bell developed the mathematical inequality - Bell Inequality which states that if there are hidden variables, the correlation between the results of a large number of measurements will never exceed a certain value.
- Quantum mechanics predicts that a certain type of experiment will violate Bell’s inequality, thus resulting in a stronger correlation than would otherwise be possible.
The Nobel Prize in Physics for 2022 was awarded to John F. Clauser, Alain Aspect and Anton Zeilinger for their work in quantum mechanics by the Royal Swedish Academy of Sciences.
- The laureates have been awarded for their experiments with entangled photons(quantum entanglement), establishing the violation of Bell inequalities, and pioneering quantum information science.
- John F. Clauser developed John Bell’s ideas, leading to a practical experiment which supported quantum mechanics by clearly violating a Bell inequalityimplying that quantum mechanics cannot be replaced by a theory that uses hidden variables.
- Alain Aspect developed the setup, using it in a way that closed an important loophole.
- He was able to switch the measurement settings after an entangled pair had left its source, so the setting that existed when they were emitted could not affect the result (as some loopholes remained after John Clauser’s experiment).
- Anton Zeilinger was chosen for his innovative use of entanglement and Bell pairsboth in research and application such as quantum cryptography.
- His research group demonstrated a phenomenon called quantum teleportation,which makes it possible to move a quantum state from one particle to the one at a distance.
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