Popper's Experiment - Realization of Popper's Experiment

Realization of Popper's Experiment

Popper's experiment was realized in 1999 by Kim and Shih using a SPDC photon source. Interestingly, they did not observe an extra spread in the momentum of particle 2 due to particle 1 passing through a narrow slit. They write:

"Indeed, it is astonishing to see that the experimental results agree with Popper’s prediction. Through quantum entanglement one may learn the precise knowledge of a photon’s position and would therefore expect a greater uncertainty in its momentum under the usual Copenhagen interpretation of the uncertainty relations. However, the measurement shows that the momentum does not experience a corresponding increase of uncertainty. Is this a violation of the uncertainty principle?"

Rather, the momentum spread of particle 2 (observed in coincidence with particle 1 passing through slit A) was narrower than its momentum spread in the initial state.

They concluded that:

"Popper and EPR were correct in the prediction of the physical outcomes of their experiments. However, Popper and EPR made the same error by applying the results of two-particle physics to the explanation of the behavior of an individual particle. The two-particle entangled state is not the state of two individual particles. Our experimental result is emphatically NOT a violation of the uncertainty principle which governs the behavior of an individual quantum."

This led to a renewed heated debate, with some even going to the extent of claiming that Kim and Shih's experiment had demonstrated that there is no non-locality in quantum mechanics.

Unnikrishnan (2001), discussing Kim and Shih's result. wrote that the result:

is a solid proof that there is no state-reduction-at-a-distance. ... Popper's experiment and its analysis forces us to radically change the current held view on quantum non-locality.

Short criticized Kim and Shih's experiment, arguing that because of the finite size of the source, the localization of particle 2 is imperfect, which leads to a smaller momentum spread than expected. However, Short's argument implies that if the source were improved, we should see a spread in the momentum of particle 2.

Sancho carried out a theoretical analysis of Popper's experiment, using the path-integral approach, and found a similar kind of narrowing in the momentum spread of particle 2, as was observed by Kim and Shih. Although this calculation did not give them any deep insight, it indicated that the experimental result of Kim-Shih agreed with quantum mechanics. It did not say anything about what bearing it has on the Copenhagen interpretation, if any.

Read more about this topic:  Popper's Experiment

Famous quotes containing the words realization of, realization, popper and/or experiment:

    Among all the modernized aspects of the most luxurious of industries, the model, a vestige of voluptuous barbarianism, is like some plunder-laden prey. She is the object of unbridled regard, a living bait, the passive realization of an ideal.... No other female occupation contains such potent impulses to moral disintegration as this one, applying as it does the outward signs of riches to a poor and beautiful girl.
    Colette [Sidonie Gabrielle Colette] (1873–1954)

    The ground for taking ignorance to be restrictive of freedom is that it causes people to make choices which they would not have made if they had seen what the realization of their choices involved.
    —A.J. (Alfred Jules)

    It is clear that everybody interested in science must be interested in world 3 objects. A physical scientist, to start with, may be interested mainly in world 1 objects—say crystals and X-rays. But very soon he must realize how much depends on our interpretation of the facts, that is, on our theories, and so on world 3 objects. Similarly, a historian of science, or a philosopher interested in science must be largely a student of world 3 objects.
    —Karl Popper (1902–1994)

    To me the sole hope of human salvation lies in teaching Man to regard himself as an experiment in the realization of God, to regard his hands as God’s hand, his brain as God’s brain, his purpose as God’s purpose. He must regard God as a helpless Longing, which longed him into existence by its desperate need for an executive organ.
    George Bernard Shaw (1856–1950)