Schroedinger's Cat
On June 7 of 1935, Erwin Schroedinger wrote to Albert Einstein to
congratulate him on what is now known as the EPR paper, a famous problem in
the interpretation of Quantum Mechanics.
Soon thereafter, he published what was to become one of the most
celebrated paradoxes in quantum theory:
Schroedinger's Cat 
A cat is placed in a box, together with a radioactive atom. If the
atom decays,
and the geiger-counter detects an alpha particle, the hammer hits a flask of
prussic acid (HCN), killing the cat. The paradox lies in the clever coupling of
quantum and classical domains. Before the observer opens the box, the cat's
fate is tied to the wave function of the atom, which is itself in a superposition
of decayed and undecayed states. Thus, said Schroedinger, the cat must itself
be in a superposition of dead and alive states before the observer opens
the box, ``observes'' the cat, and ``collapses'' it's wave function.
Feline Wave Functions
Schroedinger's Cat and the Environment:
Examples from Condensed Matter.
Mossbauer effect
X-Ray edge effect
Kondo effect
References
- E. Schroedinger, Naturwiss. 23 807, (1935), translated
to english in ``Quantum Theory and Measurement'', ed J.A. Wheeler and
W.H. Zurek, Princeton Univ Press (1983)
Last modified: May 31, 1994
Ard Louis, ardlouis@lassp.cornell.edu
