November 25, 2011
WHICH MAKES IT ALL THE FUNNIER...:Coherent Schrödinger's cat still confounds (Tim Wogan, Nov 23, 2011, Physics World)
The famous paradox of Schrödinger's cat starts from principles of quantum physics and ends with the bizarre conclusion that a cat can be simultaneously in two physical states - one in which the cat is alive and the other in which it is dead. In real life, however, large objects such as cats clearly don't exist in a superposition of two or more states and this paradox is usually resolved in terms of quantum decoherence. But now physicists in Canada and Switzerland argue that even if decoherence could be prevented, the difficulty of making perfect measurements would stop us from confirming the cat's superposition.
Erwin Schrödinger, one of the fathers of quantum theory, formulated his paradox in 1935 to highlight the apparent absurdity of the quantum principle of superposition - that an unobserved quantum object is simultaneously in multiple states. He envisaged a black box containing a radioactive nucleus, a Geiger counter, a vial of poison gas and a cat. The Geiger counter is primed to release the poison gas, killing the cat, if it detects any radiation from a nuclear decay. The grisly game is played out according to the rules of quantum mechanics because nuclear decay is a quantum process.
If the apparatus is left for a period of time and then observed, you may find either that the nucleus has decayed or that it has not decayed, and therefore that the poison has or has not been released, and that the cat has or has not been killed. However, quantum mechanics tells us that, before the observation has been made, the system is in a superposition of both states - the nucleus has both decayed and not decayed, the poison has both been released and not been released, and the cat is both alive and dead.
...when folks compare denying human-caused global warning to denying Galileo.
Posted by oj at November 25, 2011 5:03 AM