# Bell’s Theorem and Quantum Mechanics

Introduction
In 1968 an Irish Physicist, Bell, working in CERN worked out a theorem which gave us an insight into the nature of deep reality. He showed using classical probabilistic methods that reality must be non-local. What does it mean? It means that there must be instantaneous connection between interconnected quantum particles even when they are separated by vast distances. What does Bell's theorem have to say about the various interpretations of Quantum Mechanics? In order to answer this question I will present some of the
prominent Quantum Mechanics schools and then discuss the implications of Bell's theorem.
Prominent Quantum Mechanics Schools

The Copenhagen School

The Copenhagen school, founded by the Nobel laureate Niels Bohr, takes the position that there is no deep underlying reality. This school, accepted by most Physicists as outlining the orthodox view, takes the position that a quantum particle like an electron in an atom do not have any dynamic attribute (like energy, velocity etc) of its own. The attributes measured by an experiment is a joint product of the device used in the measurement and the particle. The quantum particle's attributes (not the static attribute like mass) is a product of the measurement. The deep implication of this view is that the world is created by the act of observation. This means that it makes no sense to say that the moon exists. The moon comes into being when it is observed.

Schroedinger and Bohm's views

This school views the world as an undivided whole. This view arose from the quantum concept of phase entaglement. Quantum Mechanics says that once two quantum particles have interacted, their wavefunctions cannot be separated into two forms when they move apart but are forever represented by a single wave. Thus the two waves of the two particles are entangled. This was first shown by Einstein, Podolsky and Rosen in 1937. This entanglement is superluminal since the entanglement persists even when one of the quantum particle is in the "elsewhere" region of the other particle's light cone, i,e. , there is instant connection. The question raised by Schroedinger and Bohm was whether this wholeness of representation is matched by a wholeness of being.

Doesn't superluminal phase entaglement violate Special Relativity? Most working Physicists ignore this question about the superluminal connection between two separated quantum particles since the final result is not superluminal. The instant connection between the two particles does not give rise to superluminal result, i.e., does not give rise to superluminal phenomena. Most Physicists ignore the question of whether the underlying reality is superluminal or not.

Everett's many world interpretation

In 1957 Everett, a California Institute of Technology graduate student, introduced the idea of a many world Quantum Mehcanics. In this scheme there are many universes and the probability concept of Quantum Mechanics arises because the actual wavefunction is a sum of possibilities spread over multiple universes. What is the implication of such a scheme. The implication is that all of us has clones in every universe currently existing. The Quantum Mechanics wavefunction appears to be probabilistic because we can not measure the things happening in other universes.

Neorealism

This school views the world as made up of ordinary objects. This was the position of Albert Einstein who never completely accepted Quantum Mechanics. This school is not very popular because it seems to violate special relativity. While the objects are real according to this school, a real field called pilot wave is necessary to change the attributes (like energy) of the quantum particles and must transmit information faster than light. So while the Copenhagen school says that the world comes into being through an act of observation, the neorealist school invokes superluminal real field. Moreover this field can change the attributes of the quantum particle due to changes taking place anywhere in the universe.

Consciousness creates reality

This school says that consciousness creates reality.

Implications of Bell's theorem

Bell's theorem does not resolve the debate about the validity of these schools. It does not discriminate between these schools as long as these schools accept that the deep reality is non-local. An important thing to note here is that the validity of Bell's theorem does not depend on the validity of Quantum Mechanics.

End Notes

There are many books dealing with this topic. One book is Quantum Reality by Nick Herbert. Another is "On Physics and Philosophy" by Bernard d'Espagnat.