Encyclopedia > Wigner's friend

  Article Content

Wigner's friend

Wigner's friend is a thought experiment proposed by the physicist Eugene Wigner; it is an extension of the Schrödinger's cat experiment designed to highlight unanswered questions in the Copenhagen interpretation of quantum mechanics.

In the Copenhagen interpretation, the collapse of the wavefunction is said to take place when a quantum system is measured. Essentially, the Wigner's friend experiment asks the question: at what stage does a "measurement" take place? It posits a friend of Wigner who performs the Schrödinger's cat experiment while Wigner is out of the room. Only when Wigner comes into the room does he himself know the result of the experiment: until this point, was the state of the system a superposition of "dead cat/sad friend" and "alive cat/happy friend", or was it determined at some previous point? Wigner designed the experiment to highlight the inadequacy of the idea (central to the Copenhagen interpretation) that the measurement process is somehow inherently special.

Compare quantum suicide.



All Wikipedia text is available under the terms of the GNU Free Documentation License

 
  Search Encyclopedia

Search over one million articles, find something about almost anything!
 
 
  
  Featured Article
242

... - 3rd century - 4th century Decades: 190s 200s 210s 220s 230s - 240s - 250s 260s 270s 280s 290s Years: 237 238 239 240 241 - 242 - 243 244 245 246 ...

 
 
 
This page was created in 21.6 ms