Since the inception of quantum mechanics, the many counter-intuitive aspects and results of the theory have provoked strong philosophical debates and many interpretations. Even fundamental issues, such as Max Born's basic rules concerning probability amplitudes and probability distributions, took decades to be appreciated by society and many leading scientists. Indeed, the renowned physicist Richard Feynman once said, "I think I can safely say that nobody understands quantum mechanics."
The Copenhagen interpretation—due largely to the Danish theoretical physicist Niels Bohr—remains the quantum mechanical formalism that is currently most widely accepted amongst physicists, some 75 years after its enunciation in the first quarter of the 20th century. According to this interpretation, the probabilistic nature of quantum mechanics is not a temporary feature that will eventually be replaced by a deterministic theory, but instead must be considered a final renunciation of the classical idea of "causality". It is also believed therein that any well-defined application of the quantum mechanical formalism must always make reference to the experimental arrangement, due to the complementarity nature of evidence obtained under different experimental situations.
Albert Einstein, himself one of the founders of quantum theory, disliked this loss of determinism in measurement. Einstein held that there should be a local hidden variable theory (also known as the local realism idea) underlying quantum mechanics and, consequently, that the present theory was incomplete. He produced a series of objections to the theory, the most famous of which has become known as the Einstein-Podolsky-Rosen paradox. John Bell showed that this "EPR" paradox led to experimentally testable differences between quantum mechanics and local realistic theories. Experiments have been performed confirming the accuracy of quantum mechanics, thereby demonstrating that the physical world cannot be described by any local realistic theory. The Bohr-Einstein debates and the experiments that followed provide a vibrant critique of the Copenhagen Interpretation from an epistemological point of view.
1. According to the passage, Einstein’s position regarding determinism in quantum mechanics was ___________________.
(A) unverifiable
(B) incomplete
(C) promising
(D) incorrect
(E) unfounded
2. According to the passage, all of the following are true about the Copenhagen interpretation except:
(A) It puts an important emphasis on the experimental arrangement
(B) It redefines the interpretation of cause and effect
(C) It was critiqued by both Einstein and Bohr
(D) It is well regarded in the scientific community
(E) It is difficult to understand
3. Which of the following can be inferred about the local hidden variable theory?
(A) It replaced most components of quantum theory
(B) It was mostly in line with John Bell’s discoveries
(C) It was proven by the Einstein-Podolsky-Rosen parado
(D) It predicted more determinism in measurement than quantum theory
(E) It agreed mainly with the predictions of Niels Bohr
4. The primary purpose of the passage above is to:
(A) Show that Einstein was wrong about quantum mechanics
(B) Discuss an important debate on one of the most challenging scientific theories of the 20th century
(C) Highlight the importance of quantum mechanics in the field of physics
(D) Illustrate how perplexing quantum mechanics is for scientists
(E) Argue that the Copenhagen interpretation is correct
5. Which of the following can be inferred about the Copenhagen interpretation of quantum mechanics?
(A) It views the probabilistic nature of quantum mechanics as temporary.
(B) It involves some loss of determinism in measurement.
(C) It was widely accepted when it was enunciated 75 years ago.
(D) It views the experimental arrangement as unimportant.
(E) It rejected many of Albert Einstein’s views and theories.
Solution
Explanation: The Copenhagen interpretation was primarily discussed in the 2nd paragraph (and in the 3rd) so you should focus your attention there. (A) is contradicted in the second sentence of the second paragraph. It says that according to this interpretation the probabilistic nature is NOT temporary. (B), the correct answer, requires that you leverage the first sentence of the 3rd paragraph in combination with the second paragraph. In that sentence you learn that “Albert Einstein…disliked this loss of determinism in measurement” in reference back to the Copenhagen interpretation. From that you know that the Copenhagen interpretation involved some loss of determinism. For (C), you learn in the passage that it is widely accepted today, but you have no idea if that was the case 75 years ago. (D), like (A), is directly contradicted in the 2nd paragraph – it states that the arrangement IS important. For (E), you know that Albert Einstein did not like the loss of determinism in the Copenhagen interpretation, but you have no idea if the Copenhagen interpretation rejected MANY of his views and theories. Correct answer is (B).
6. According to the passage, it can be inferred that Albert Einstein believed all of the following EXCEPT:
(A) the local hidden variable theory was an essential component in a complete theory of quantum mechanics.
(B) Niels Bohr was incorrect in some part of his interpretation of quantum mechanics.
(C) the Copenhagen interpretation of quantum mechanics was incomplete.
(D) experimentally testable differences exist between quantum mechanics and local realistic theories.
(E) some components of the quantum mechanics theory were correct.
From your mental map of this passage, you should recognize that for this question, you need to look mostly in the last paragraph since that is the only place where Einstein is mentioned. As with any EXCEPT question, your job is to find evidence in the passage for or against each answer choice and carefully use process of elimination.
Choice (A) can be confirmed based on this sentence: “Einstein held that there should be a local hidden variable theory underlying quantum mechanics and, consequently, that the present theory was incomplete.” Since Einstein believed that without local hidden variable theory, quantum theory is incomplete, he must believe that it is essential to quantum theory. Because (A) is supported by the passage, it can be eliminated.
For (B), Einstein had issues with some part of the Copenhagen interpretation (he believes that it is incomplete), and therefore with the ideas of Bohr, one of its primary architects. The passage also references the “Bohr-Einstein debates” at the end of the last paragraph. From this you know Albert Einstein clashed about some part of theory and that Einstein believed that Bohr was incorrect about some portion of his interpretation. You can therefore eliminate choice (C).
(C) is fairly easy to prove as it is explicitly stated in the second sentence of the last paragraph and can be eliminated.
(D), the correct answer, is tricky. While it is discussed in the last paragraph, you do not know if Einstein believed it. It was John Bell who showed these experimentally testable differences and that those differences contradicted Einstein. However, the passage doesn’t mention whether Einstein accepted Bell’s work. Thus (D) is the one choice that you cannot conclude regarding Einstein’s beliefs.
For (E), since Einstein was one of the founders of quantum mechanics, you can be sure that he agreed with some of its components. The correct answer is (D).
7. The passage suggests which of the following:
(A) Niels Bohr and Max Born would most likely agree on rules concerning probability amplitudes
(B) Richard Feynman and Albert Einstein would most likely disagree about the difficulties relating to quantum mechanics
(C) Niels Bohr and Albert Einstein would most likely disagree about most aspects of quantum mechanics
(D) John Bell and Albert Einstein would most likely disagree about quantum mechanics
(E) Albert Einstein and Niels Bohr would most likely disagree about determinism in measurement
Solution: E
Explanation: To answer this question, you must examine each agreement/disagreement in the answer choices and look for confirmation in the passage.
(E) is the only one that is guaranteed because determinism in measurement was the exact portion of the quantum theory that the two men disagreed upon.
For (A), no information is given about how Bohr feels about Born’s rules. Likewise in (B), no comparison is given between Feynman and Einstein.
(C) and (D) are both too strong as Bohr and Einstein almost surely do agree about many aspects (they were both involved in its development) but just disagree about determinism in measurement, and Bell and Einstein may or may not agree on quantum mechanics.
All you know is that Bell determined that it would be possible to see who is correct. Answer is (E).
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Updated on: 02 Apr 2020, 03:37
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