The spookiness of quantum entanglement emerges from the fact of quantum superposition, and was clear to the founding fathers of quantum mechanics who developed the idea within the Twenties and Thirties.
To create entangled particles you primarily break a system into two, the place the sum of the components is thought. For instance, you may cut up a particle with spin of zero into two particles that essentially could have reverse spins in order that their sum is zero.
In 1935, Albert Einstein, Boris Podolsky and Nathan Rosen published a paper that describes a thought experiment designed as an instance a seeming absurdity of quantum entanglement that challenged a foundational regulation of the universe.
A simplified version of this thought experiment, attributed to David Bohm, considers the decay of a particle known as the pi meson. When this particle decays, it produces an electron and a positron which have reverse spin and are shifting away from one another. Due to this fact, if the electron spin is measured to be up, then the measured spin of the positron might solely be down, and vice versa. That is true even when the particles are billions of miles aside.
This might be advantageous if the measurement of the electron spin had been at all times up and the measured spin of the positron had been at all times down. However due to quantum mechanics, the spin of every particle is each half up and half down till it’s measured. Solely when the measurement happens does the quantum state of the spin “collapse” into both up or down – instantaneously collapsing the opposite particle into the alternative spin. This appears to recommend that the particles talk with one another by some signifies that strikes quicker than the velocity of sunshine. However in keeping with the legal guidelines of physics, nothing can journey quicker than the velocity of sunshine. Certainly the measured state of 1 particle can not instantaneously decide the state of one other particle on the far finish of the universe?
Physicists, together with Einstein, proposed quite a few different interpretations of quantum entanglement within the Thirties. They theorized there was some unknown property – dubbed hidden variables – that determined the state of a particle before measurement. However on the time, physicists didn’t have the expertise nor a definition of a transparent measurement that might check whether or not quantum concept wanted to be modified to incorporate hidden variables.
