Schrödinger's Cat

INTRODUCTION

Erwin Schrödinger

Schrödinger's Cat is a thought experiment which was devised by the Austrian physicist ERWIN SCHRÖDINGER in 1935. The thought experiment presents a cat that might be alive or dead, depending on an earlier random event.


PURPOSE
The above experiment illustrates the problem of the Copenhagen Interpretation of quantum mechanics when applied to everyday objects.


CONSTRUCTION
A cat along with a flask filled with a poison and a radioactive source is placed in a sealed box. A Geiger Counter is placed inside the box to detect radiation. The flask shatters when the radiation is detected. Due to the breaking of flask the poison is released in the box thereby killing the cat. Standing with Copenhagen Interpretation of the quantum mechanics implies that after a while, the cat is simultaneously alive & dead, contradicting the common experience.


EXPLANATION

Superposition of
two states

In common observation, a person defines or describes only one state of a system which is well-defined by a wave function associated with the system. As an example imagine a tree in a forest. Whether the tree in forest is standing or has fallen, either of two can be associated but not both. At particular instant of time, a system has only one state.


In Copenhagen Interpretation of quantum mechanics, a system stops being a superposition of two states and becomes either of two when an observation is made. This clearly shows that the wave function collapses to a single value whenever a conscious observation is made. Copenhagen Interpretation is an observer induced collapse.
When the cat is sealed inside the box, it is alive. Now after a while, there are two states that can be associated to the system(containing cat & flask)-"decayed nucleus/dead cat" or "undecayed nucleus/alive cat". The decay of the radioactive substance is small, may be one atom per hour. Now, when the box is opened, i.e. an observation is made, so the wave function of two states for a single system collapses into one state. If the atom has not decayed, then the cat is alive and if the atom has decayed, the cat is dead.

Collapse of the Wave Function

Another Video : http://www.youtube.com/watch?v=HCOE__N6v4o