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The essay cites this thought experiment to back up that quote: https://en.wikipedia.org/wiki/Renninger_negative-result_experiment https://en.wikipedia.org/wiki/

by n4r9 4y ago

The essay cites this thought experiment to back up that quote: https://en.wikipedia.org/wiki/Renninger_negative-result_experiment https://en.wikipedia.org/wiki/Renninger_negative-result_expe... The idea is that by clever positioning of detectors, it is possible to make a quantum observation before the detection physically occurs. That challenges the notion that wave-function collapse is a result of instruments interfering with the system. This doesn't imply that the system "knows" anything about the conscious mind observing it. Very few physicists actually believe that consciousness affects physical mechanisms in this way. A more plausible interpretation may be that the wave-function collapse represents a belief-update process on the part of the observing agent.

prox 4y ago
What is a “belief-update on the part of the observing agent” Can you clarify?
- n4r9 4y ago
  There is a class of interpretations of quantum theory which take a so-called epistemic perspective of the wave-function. In the epistemic perspective, the wave function represents an agent's knowledge, belief or information regarding a system. This has a lot of appeal partly because wave function collapse looks very similar to the way that probabilities are updated in bayesian statistics when new information comes to light. For example, if I measure the polarisation of a photon in the vertical component and get a "yes" results (V1=y), then I have complete confidence that future measurements of the vertical will again get a "yes" result (V2=y), whereas future measurements of the horizontal component will be 50-50 between a "yes" result (H2=y) and a "no" result (H2=n). P(V2=y | V1=y) = 1 P(V2=n | V1=y) = 0 P(H2=y | V1=y) = 0.5 P(H2=n | V1=y) = 0.5 You can sum this up as "the wave function is a way for me to keep track of probabilities, rather than an objective fact about the system". Of course this idea has its own set of challenges. For many people the question becomes "what does the wave function represent knowledge of"? Also, a few years ago there was a thought-experiment known as the PBR theorem, which rules out some epistemic interpretations: https://en.wikipedia.org/wiki/PBR_theorem https://en.wikipedia.org/wiki/PBR_theorem There is a good set of slides on the PBR theorem and its implications by Jon Barrett here (he was my external viva examiner): http://www.cs.ox.ac.uk/qisw2012/slides/barrett.pdf http://www.cs.ox.ac.uk/qisw2012/slides/barrett.pdf One class of epistemic interpretations that persists are the so-called bayesian interpretations of quantum theory: https://en.wikipedia.org/wiki/Quantum_Bayesianism https://en.wikipedia.org/wiki/Quantum_Bayesianism . A "strong" version of quantum bayesianism is QBism, which asserts that quantum theory is no more than an effective user manual for organising subjective beliefs about the outcomes of future interactions with the world. Chris Fuchs and Ruediger Schack are two prominent theorists advocating QBism.
  - prox 4y ago
    Wow! Down the rabbit hole we go! Looks like I got some reading to do. I love this topic.

by n4r9 4y ago

prox 4y ago

What is a “belief-update on the part of the observing agent” Can you clarify?

n4r9 4y ago
There is a class of interpretations of quantum theory which take a so-called epistemic perspective of the wave-function. In the epistemic perspective, the wave function represents an agent's knowledge, belief or information regarding a system. This has a lot of appeal partly because wave function collapse looks very similar to the way that probabilities are updated in bayesian statistics when new information comes to light. For example, if I measure the polarisation of a photon in the vertical component and get a "yes" results (V1=y), then I have complete confidence that future measurements of the vertical will again get a "yes" result (V2=y), whereas future measurements of the horizontal component will be 50-50 between a "yes" result (H2=y) and a "no" result (H2=n). P(V2=y | V1=y) = 1 P(V2=n | V1=y) = 0 P(H2=y | V1=y) = 0.5 P(H2=n | V1=y) = 0.5 You can sum this up as "the wave function is a way for me to keep track of probabilities, rather than an objective fact about the system". Of course this idea has its own set of challenges. For many people the question becomes "what does the wave function represent knowledge of"? Also, a few years ago there was a thought-experiment known as the PBR theorem, which rules out some epistemic interpretations: https://en.wikipedia.org/wiki/PBR_theorem https://en.wikipedia.org/wiki/PBR_theorem There is a good set of slides on the PBR theorem and its implications by Jon Barrett here (he was my external viva examiner): http://www.cs.ox.ac.uk/qisw2012/slides/barrett.pdf http://www.cs.ox.ac.uk/qisw2012/slides/barrett.pdf One class of epistemic interpretations that persists are the so-called bayesian interpretations of quantum theory: https://en.wikipedia.org/wiki/Quantum_Bayesianism https://en.wikipedia.org/wiki/Quantum_Bayesianism . A "strong" version of quantum bayesianism is QBism, which asserts that quantum theory is no more than an effective user manual for organising subjective beliefs about the outcomes of future interactions with the world. Chris Fuchs and Ruediger Schack are two prominent theorists advocating QBism.
- prox 4y ago
  Wow! Down the rabbit hole we go! Looks like I got some reading to do. I love this topic.