Jun 23, 2024 04:31 AM
https://iai.tv/articles/the-many-answers..._auid=2020
INTRO: The measurement problem in quantum mechanics has challenged physicists and philosophers for almost a century. The measurement problem refers to the probablistic collapse of the deterministic wave function. It has been a focal point of debate in the philosophy of physics, engaging minds from Richard Feynman to Sir Roger Penrose. We now have a plethora of interpretations. Join Mario Barbatti as he argues that, while the quantum measurement problem is not completely solved, the proposed solutions are beginning to bear fruit.
EXCERPTS: [...] The first of Greene’s guests was the philosopher of physics, Elise Crull. She invoked decoherence to solve it. In the second debate, the physicist Sean Caroll claimed that the measurement problem is solved by the many-worlds hypothesis. He also dismissively admitted the existence of alternatives like objective collapse theories. The last debate was with the physicist Carlo Rovelli, who champions the relational interpretation, where the quantum state status, collapsed or superposed, is relative to the observer...
[...] Decoherence is part of standard quantum mechanics (although einselection is still a topic for research). It is an experimentally well-documented effect, crucial for quantum mechanical applications, such as quantum computing. Regardless of one’s preferred interpretation, the role of decoherence must always be considered.
We can also draw some insightful implications from decoherence. [...] Decoherence clears up a significant portion of the measurement problem. Nevertheless, it does not solve the third question. After the superposition is suppressed and the basis is chosen, the system rests on a mixture of possible outcomes. Decoherence does not provide any information on how and why only one of these outcomes is measured.
For some interpretations, this is not a problem. The many-worlds interpretation Caroll promoted, for instance, proposes that the remaining outcomes after decoherence correspond to independent universe branches...
[...] The many-worlds interpretation acquired somewhat shabby fame due to lazy sci-fi TV shows. Moreover, many people also feel threatened by the exuberant idea that we exist in parallel realities. (As for myself, I am captivated by the possibility that each of us is an infinitely branched holistic quantum being.) Despite the resistance, the many-worlds interpretation is a serious contender among the proposed solutions to the measurement problem. It is entirely consistent with standard quantum mechanics, and it does not require any modification of the theory. However, it must always be considered an interpretation (as opposed to a theory) as long as we cannot find a way to test it.
For the many-worlds interpretation, the quantum state has physical reality. Other interpretations take the opposite path. They claim that the quantum state is no more than a mathematical tool to predict outcomes. This is the stance of Rovelli’s relational interpretation and other interpretations as quantum Bayesianism, QBism for short.
Relational interpretation focuses on the interaction between systems. Properties, it claims, are only defined by the relation between the systems. [...] QBism takes a hard turn toward subjectivism. It considers that the quantum state only reflects the amount of our knowledge about the system... Just like in many worlds, we know no way to test relational interpretation and QBism. They must also be regarded as interpretations. Both are also entirely consistent with standard quantum mechanics.
The situation is profoundly distinct when dealing with the objective collapse theories. Those are, in fact, theories, not interpretations. They change the Schrödinger equation to account for the collapse. [...] Objective collapse theories can be tested and eventually disproved...
[...] The highest stakes among the objective collapse theories are with the Diósi-Penrose model. This theory claims that gravity is behind the term in the modified Schrödinger equation that induces collapse. ... The Diósi-Penrose hypothesis has profound implications for physics. If it is proven, it means that gravity plays an exceptional role in nature. It would not only settle the measurement problem but also impact any future attempts at reconciling general relativity and quantum mechanics.
[...] Gladly, today, the measurement problem is much less enigmatic than it was before decoherence was understood. Thanks to it, we know how the outcome basis is selected environmentally and why quantum interference is not easily observed. However, the measurement problem is still not entirely solved. We still cannot explain how and why we observe a single outcome... (MORE - missing details)
INTRO: The measurement problem in quantum mechanics has challenged physicists and philosophers for almost a century. The measurement problem refers to the probablistic collapse of the deterministic wave function. It has been a focal point of debate in the philosophy of physics, engaging minds from Richard Feynman to Sir Roger Penrose. We now have a plethora of interpretations. Join Mario Barbatti as he argues that, while the quantum measurement problem is not completely solved, the proposed solutions are beginning to bear fruit.
EXCERPTS: [...] The first of Greene’s guests was the philosopher of physics, Elise Crull. She invoked decoherence to solve it. In the second debate, the physicist Sean Caroll claimed that the measurement problem is solved by the many-worlds hypothesis. He also dismissively admitted the existence of alternatives like objective collapse theories. The last debate was with the physicist Carlo Rovelli, who champions the relational interpretation, where the quantum state status, collapsed or superposed, is relative to the observer...
[...] Decoherence is part of standard quantum mechanics (although einselection is still a topic for research). It is an experimentally well-documented effect, crucial for quantum mechanical applications, such as quantum computing. Regardless of one’s preferred interpretation, the role of decoherence must always be considered.
We can also draw some insightful implications from decoherence. [...] Decoherence clears up a significant portion of the measurement problem. Nevertheless, it does not solve the third question. After the superposition is suppressed and the basis is chosen, the system rests on a mixture of possible outcomes. Decoherence does not provide any information on how and why only one of these outcomes is measured.
For some interpretations, this is not a problem. The many-worlds interpretation Caroll promoted, for instance, proposes that the remaining outcomes after decoherence correspond to independent universe branches...
[...] The many-worlds interpretation acquired somewhat shabby fame due to lazy sci-fi TV shows. Moreover, many people also feel threatened by the exuberant idea that we exist in parallel realities. (As for myself, I am captivated by the possibility that each of us is an infinitely branched holistic quantum being.) Despite the resistance, the many-worlds interpretation is a serious contender among the proposed solutions to the measurement problem. It is entirely consistent with standard quantum mechanics, and it does not require any modification of the theory. However, it must always be considered an interpretation (as opposed to a theory) as long as we cannot find a way to test it.
For the many-worlds interpretation, the quantum state has physical reality. Other interpretations take the opposite path. They claim that the quantum state is no more than a mathematical tool to predict outcomes. This is the stance of Rovelli’s relational interpretation and other interpretations as quantum Bayesianism, QBism for short.
Relational interpretation focuses on the interaction between systems. Properties, it claims, are only defined by the relation between the systems. [...] QBism takes a hard turn toward subjectivism. It considers that the quantum state only reflects the amount of our knowledge about the system... Just like in many worlds, we know no way to test relational interpretation and QBism. They must also be regarded as interpretations. Both are also entirely consistent with standard quantum mechanics.
The situation is profoundly distinct when dealing with the objective collapse theories. Those are, in fact, theories, not interpretations. They change the Schrödinger equation to account for the collapse. [...] Objective collapse theories can be tested and eventually disproved...
[...] The highest stakes among the objective collapse theories are with the Diósi-Penrose model. This theory claims that gravity is behind the term in the modified Schrödinger equation that induces collapse. ... The Diósi-Penrose hypothesis has profound implications for physics. If it is proven, it means that gravity plays an exceptional role in nature. It would not only settle the measurement problem but also impact any future attempts at reconciling general relativity and quantum mechanics.
[...] Gladly, today, the measurement problem is much less enigmatic than it was before decoherence was understood. Thanks to it, we know how the outcome basis is selected environmentally and why quantum interference is not easily observed. However, the measurement problem is still not entirely solved. We still cannot explain how and why we observe a single outcome... (MORE - missing details)