Wheeler\'s delayed choice (Introduction)
by David Turell 
, Thursday, August 08, 2013, 23:53 (4125 days ago)
Since one of Ruth's papers is based on Wheeler's famous gedanken experiment I thought I would present a good website description:-"In summary, we have chosen whether to know which slit the particle went through, by choosing to use the telescopes or not, which are the instruments that would give us the information about which slit the particle went through. We have delayed this choice until a time after the particles "have gone through one slit or the other slit or both slits," so to speak. Yet, it seems paradoxically that our later choice of whether to obtain this information determines whether the particle passed through one slit or the other slit or both slits, so to speak. If you want to think of it this way (I don't recommend it), the particle exhibited after-the-fact wave-like behavior at the slits if you chose the screen; and it exhibited after-the-fact particle-like behavior at the slits if you chose the telescopes. Therefore, our delayed choice of how to measure the particle determines how the particle actually behaved at an earlier time."- http://www.bottomlayer.com/bottom/basic_delayed_choice.htm
Wheeler\'s delayed choice; quantum eraser
by David Turell , Friday, August 09, 2013, 00:18 (4125 days ago) @ David Turell
http://www.bottomlayer.com/bottom/kim-scully/kim-scully-web.htm#fig2-This shows we can choose what information we want, but it does not imply to me that our consciousness creates that information, an implication I have seen in the past.-"Time 6. Upon accessing the information gathered by the Coincidence Circuit, we the observer are shocked to learn that the pattern shown by the positions registered at D0 at Time 2 depends entirely on the information gathered later at Time 4 and available to us at the conclusion of the experiment. -The position of a photon at detector D0 has been registered and scanned. Yet the actual position of the photon arriving at D0 will be at one place if we later learn more information; and the actual position will be at another place if we do not. -Ho-hum. Another experimental proof of QM. This is the way it works, folks"
Wheeler's delayed choice; another explanation
by David Turell , Thursday, March 10, 2016, 20:03 (3180 days ago) @ David Turell
New experiments can do his thought experiment and prove a particle is both wave and particle:-https://www.sciencedaily.com/releases/2016/03/160310111857.htm-"To put this concept into a concrete setting, Wheeler proposed his famous delayed-choice thought experiment. In this thought experiment, the choice to determine the particle or wave nature is delayed or even changed during the experiment. Thereby, one and the same phenomenon, for instance light, manifests itself as a particle or as a wave in the same experiment. It can therefore indeed be both, depending on the time and nature of the measurement.-"In the past decades, quantum physicists have tried to experimentally test Wheeler's thought experiment to empirically substantiate the wave-particle duality. Xiao-song Ma from the Nanjing University, Johannes Kofler from the Max Planck Institute of Quantum Optics, and Anton Zeilinger from the University of Vienna and the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences have now shown the success of this endeavor in an extensive study, which sums up and evaluates the whole history of delayed choice experiments.-To put this concept into a concrete setting, Wheeler proposed his famous delayed-choice thought experiment. In this thought experiment, the choice to determine the particle or wave nature is delayed or even changed during the experiment. Thereby, one and the same phenomenon, for instance light, manifests itself as a particle or as a wave in the same experiment. It can therefore indeed be both, depending on the time and nature of the measurement.-"In the past decades, quantum physicists have tried to experimentally test Wheeler's thought experiment to empirically substantiate the wave-particle duality. Xiao-song Ma from the Nanjing University, Johannes Kofler from the Max Planck Institute of Quantum Optics, and Anton Zeilinger from the University of Vienna and the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences have now shown the success of this endeavor in an extensive study, which sums up and evaluates the whole history of delayed choice experiments."-Comment: The wave or particle form depends on the mode of observation.