[Physics Class Notes] on Bell’s Theorem Pdf for Exam

What Does Bell Theorem Mean?

According to a scientist named Bell, for local hidden variables, there is no corporal concept that can propagate the quantum mechanics calculations.

The Physicist, John Stewart Bell brought up a theorem, and later on, it was named as Bell’s theorem. There are some microscopic properties present inside a particle known as hidden variables. 

In general, for microscopes (existing microscopes), it is very difficult to keep an eye on them and study their behavior. 

A Physicist known as Heisenberg stated the Uncertainty Principle. According to his principle, there is no existence of variables outside the context of observation.

Quantum mechanics had no scope in the inacceptable situation after EPR. The EPR quantum mechanics was imperfect in the logic that it botched to version for some rudiments of physical reality. Also, it has desecrated the principle of the finite propagation speed of physical effects. 

Bell’s Theorem Formula

A formula has been developed by John Stewart Bell to measure the subatomic phenomenon. 

The formula is:

P (X = Y) + P (Y = Z) + P (Z = X) ≥ 1

Here, 

X, Y, and Z = Photon measurement variables

Mathematically, 

P (X = Y) is the probability of X = Y (applicable)

Bell’s Theorem Experiment 

Two observers, commonly known as Alice and Bob, have taken part in the EPR assumed experiment. The EPR performs in liberated quantities of spin on a pair of electrons, equipped at a source in an unusual state known as a spin-singlet state.

Bell has found a definite inference of EPR. Alice calculated the spin in the x-direction along with Bob’s measurement in the x-direction. It was measured with confidence whereas instantaneously before the measurement of Alice, the result of Bob resulted statistically merely. 

Through the experiment, he depicted a statement which stated that “when the spin is in the x-direction but not an element of physical reality, the properties pass from Alice to Bob rapidly.

According to Bell, the entangled particles communicate with each other faster than light. If we believe about anything that can go faster than light, we are wrong as per scientists since nothing goes faster than light.

Bell’s Theorem Proof states about the particle getting twisted out.

What is Bell’s Inequality?

We can learn and explain Bell’s inequality with the help of quantum mechanics. The behavior of electrons inside a magnetic field is quite interesting. We can study them with the help of quantum mechanics. 

The result of the electron inside the magnetic field sets them apart as half of the electron goes towards the right side, and the other half of the electrons go towards the left.

Again, the electrons which are situated at the right side are sent towards another magnetic field, which is perpendicular to the left.

Also, they get separated in a different way that few of them go down, and few of them go up. This randomness of electrons can be studied with the help of Bell’s theorem. 

What is Local Realism?

To prove and explain Bell’s theorem; a concept is used known as Local realism with Asis and Barsha (the consequence of random specimens). 

Sita and Ramesh have seen two values with the help of a detector setting. The observed values are A (a, λ) and b is B (b, λ), respectively.

So, the expression that states about local realism, 

E(X) = ∫