What’s Wrong with Schrodinger’s Cat?

Schrodinger argued that as the cat is entangled with the atom and shares the same wave function, before an observation is made, the cat is both alive and dead. When an observer opens the door of the chamber the wave function collapses and the cat could be seen either dead or alive. However until the observer opens the door the cat is both dead and alive.
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by Prof. Nalin de Silva

(February 22, Colombo, Sri Lanka Guardian) Schrodinger in his famous 1935 paper that dealt with the Copenhagen interpretation of Quantum Mechanics introduced the concept of entanglement in order to show that Bohr's interpretation did not meet the requirements imposed by reality, especially on macro objects. He proposed an "experiment" in which a cat (now known as Schrodinger's cat) is kept in a closed chamber with radio active atoms in a Geiger tube that is attached to a hammer placed above a bottle that contains a poisonous gas. The apparatus is set up so that when an atom decays the Geiger counter is activated and the hammer comes down on the bottle releasing the poisonous gas and killing the poor cat.

According to Schrodinger the cat is made of atoms and hence the cat is entangled to the atoms in the Geiger tube. Thus the state of the atoms and the cat is represented by a single wave function. An atom could decay during a certain time interval that depends on the number of atoms in the Geiger tube and the half life of the atoms. However according to the Copenhagen interpretation before an observation is made the atom would be in a state of superposition where the atom is both decayed and not decayed. The wave function representing the atom satisfies the principle of superposition and is the sum of two functions representing the decayed state and the non decayed state. The wave function collapses and takes one of the forms only at the point of observation.

Schrodinger argued that as the cat is entangled with the atom and shares the same wave function, before an observation is made, the cat is both alive and dead. When an observer opens the door of the chamber the wave function collapses and the cat could be seen either dead or alive. However until the observer opens the door the cat is both dead and alive.

Since Schrodinger proposed this experiment, though the actual experiment has not been executed, systems of entangled particles have been created and some of the concepts involved are becoming clear. For example, from the experiments of Monroe, Bennet and others, since 1995, it is clear that not all systems are entangled. Entangled systems are created only under special circumstances, and mere keeping of two or more particles (objects) in a chamber together does not guarantee the entanglement of the particles (objects). Though a particle could be in two or more states simultaneously represented by a wave function in accordance with the principle of superposition, a principle that is used in quantum computations, it does not imply that any two particles would be in an entangled state. It is suggested, in this paper, that Schrodinger has applied entanglement to a system (cat and the atoms in the Geiger tube) that is not entangled. In the absence of the bottle containing the poisonous gas, even if an atom is decayed the cat does not necessarily die. Also if the chamber is very large and if the cat is far away from the bottle in which only a very small amount of poisonous gas is stored, it is possible that the cat would not die as a result of the decaying of the atom. The non-entanglement of the system is further illustrated by the fact that the death of the cat does not necessarily imply the decay of an atom, as the cat could die due to reasons other than poisoning. It is possible for an observer to open the door of the chamber and find the cat dead without an atom being decayed, leading to the inference that the dead cat is not necessarily entangled with a decayed atom.