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Fortschritte der Physik

Experimental Realization of Popper's Experiment - Violation of The Uncertainty Principle?

Yanhua H. Shih, Yoon-Ho Kim

Published May 1, 2000• 37 citations

Abstract

Uncertainty, being perhaps the most basic principle of quantum mechanics, distinguishes the world of quantum phenomena from the realm of classical physics. Quantum entanglement, being perhaps the most surprising consequence of quantum mechanics, on the other hand apparently suggests paradoxes relating to or violations of the quantum mechanical uncertainty principle in some experimental situations. Popper's thought experiment is an example. We wish to report a recent realization of Popper's experiment. The experimental data show that there appears to be a violation of the uncertainty principle. This is, however as we shall argue in this paper, only an illusion provided that we take the teachings of quantum mechanics seriously.

DOI: 10.1002/(sici)1521-3978(200005)48:5/7<463::aid-prop463>3.0.co;2-k

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Comment on "Experimental realization of Popper's experiment: Violation of the uncertainty principle?"

Short, A. J.

Application of the uncertainty principle to conditional measurements is investigated, and found to be valid for measurements on separated sub-systems. In light of this, an apparent violation of the uncertainty principle obtained by Kim and Shih in their realization of Popper's experiment (quant-ph/9905039) is explained through analogy with a simple optical system.

arXiv:quant-ph/0005063•May 16, 2000•0 citations

Experimental realization of Popper's Experiment: Violation of the Uncertainty Principle?

Yoon-Ho Kim, Yanhua H. Shih

An entangled pair of photons (1 and 2) are emitted to opposite directions. A narrow slit is placed in the path of photon 1 to provide precise knowledge of its position on the $y$ axis and this also determines the precise $y$ position of its twin, photon 2, due to quantum entanglement. Is photon 2 going to experience a greater uncertainty in momentum, i.e., a greater $Δp_{y}$, due to the precise knowledge of its position $y$? The experimental data shows $ΔyΔp_{y}

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Popper's experiment and the interpretation of quantum mechanics.

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Popper invented a thought experiment that is alleged to test the Copenhagen interpretation of Quantum mechanics, though not the theory itself. In particular it is alleged to test the application of the Heisenberg uncertainty principle to indirect measurements. The experiment is similar to the EPR thought experiment, but it suffers from some technical flaws. These flaws are examined to see if they affect the validity of the argument; so long as they can be alleviated by technical means, the argument retains its force. The experiment has been recently instantiated, with some resolutions of these technical flaws. The results, on face value seem to vindicate Popper and to indicate a violation of the uncertainty principle. Nevertheless, Kim and Shih, who carried out the experiment, give their own interpretation that suggests that the principle should be considered intact but that the correct way to understand the results is to adopt a new metaphysics. Others suggest different reasons why the results do not amount to a violation of the uncertainty principle. Despite a variety of responses, which are carefully examined, the general point that an interpretation cannot alter the empirical basis of a theory is shown to be true. The importance of Rigolid's work in this connection is emphasized.

•Jan 1, 2007•1 citation

Uncertainty, being perhaps the most basic principle of quantum mechanics, distinguishes the world of quantum phenomena from the realm of classical physics. Quantum entanglement, being perhaps the most surprising consequence of quantum mechanics, on the other hand apparently suggests paradoxes relating to or violations of the quantum mechanical uncertainty principle in some experimental situations. Popper's thought experiment is an example. We wish to report a recent realization of Popper's experiment. The experimental data show that there appears to be a violation of the uncertainty principle. This is, however as we shall argue in this paper, only an illusion provided that we take the teachings of quantum mechanics seriously.

An entangled pair of photons (1 and 2) are emitted to opposite directions. A narrow slit is placed in the path of photon 1 to provide precise knowledge of its position on the

y

axis and this also determines the precise

y

position of its twin, photon 2, due to quantum entanglement. Is photon 2 going to experience a greater uncertainty in momentum, i.e., a greater

\Delta p_{y}

, due to the precise knowledge of its position

y

? The experimental data shows $\Delta y\Delta p_{y}<\hbar $ for photon 2. Can this recent realization of the historical thought experiment of Karl Popper signal a violation of the uncertainty principle?

An entangled pair of photon 1 and 2 are emitted in opposite directions along the positive and negative x -axis. A narrow slit is placed in the path of photon 1 which provides precise knowledge about its position along the y -axis and because of the quantum entanglement this in turn provides precise knowledge of the position y of its twin, photon 2. Does photon 2 experience a greater uncertainty in its momentum, i.e., a greater Δ p y , due to the precise knowledge of its position y ? This is the historical thought experiment of Sir Karl Popper which was aimed to undermine the Copenhagen interpretation in favor of a realistic viewpoint of quantum mechanics. Thispaper reports an experimental realization of the Popper’s experiment. One may not agree with Popper’s position on quantum mechanics; however, it calls for a correct understanding and interpretation of the experimental results. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

An entangled pair of photons (1 and 2) are emitted to opposite directions. A narrow slit is placed in the path of photon 1 to provide precise knowledge of its position on the

y

axis and this also determines the precise

y

position of its twin, photon 2, due to quantum entanglement. Is photon 2 going to experience a greater uncertainty in momentum, i.e., a greater

Δp_{y}

, due to the precise knowledge of its position

y

? The experimental data shows $ΔyΔp_{y}

Popper invented a thought experiment that is alleged to test the Copenhagen interpretation of Quantum mechanics, though not the theory itself. In particular it is alleged to test the application of the Heisenberg uncertainty principle to indirect measurements. The experiment is similar to the EPR thought experiment, but it suffers from some technical flaws. These flaws are examined to see if they affect the validity of the argument; so long as they can be alleviated by technical means, the argument retains its force. The experiment has been recently instantiated, with some resolutions of these technical flaws. The results, on face value seem to vindicate Popper and to indicate a violation of the uncertainty principle. Nevertheless, Kim and Shih, who carried out the experiment, give their own interpretation that suggests that the principle should be considered intact but that the correct way to understand the results is to adopt a new metaphysics. Others suggest different reasons why the results do not amount to a violation of the uncertainty principle. Despite a variety of responses, which are carefully examined, the general point that an interpretation cannot alter the empirical basis of a theory is shown to be true. The importance of Rigolid's work in this connection is emphasized.