The Two-State Vector Formalism

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Discussion Overview

The discussion revolves around the Two-State Vector Formalism (TSVF) and its implications regarding the nature of the universe, specifically whether it is probabilistic or deterministic. Participants explore the interpretation of TSVF in the context of quantum mechanics, addressing its relationship to established interpretations like Copenhagen and discussing the role of retro-causality.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants question whether the universe is probabilistic or determined according to the TSVF.
  • One participant notes that equation 13.9 in a referenced paper provides probabilities for measurement results, suggesting a probabilistic aspect.
  • Another participant argues that the TSVF implies determinism, as both forwards and backwards evolving wave functions follow deterministic laws, but acknowledges that reality may appear probabilistic without knowledge of the backwards wave function.
  • There is a suggestion that the TSVF is a re-packaging of the Copenhagen interpretation rather than a new interpretation, as it does not aim to resolve the measurement problem.
  • Concerns are raised about the use of weak measurements in supporting the deterministic view, with one participant citing skepticism from Charles Bennett regarding the interpretation of TSVF and the concept of backwards causation.
  • Some participants express that the differences between interpretations may be more aesthetic and philosophical rather than scientific, with a call for clarity on the nature of determinism in TSVF.
  • One participant concludes that after evaluating various interpretations, indeterministic consistent histories seem to make the most sense.

Areas of Agreement / Disagreement

Participants express differing views on whether the TSVF supports a deterministic or probabilistic universe. While some argue for determinism, others highlight the indeterministic implications of retro-causality and the interpretation of weak measurements. No consensus is reached on the nature of the universe according to TSVF.

Contextual Notes

Participants note that the interpretation of TSVF is complex and may depend on specific definitions and assumptions regarding determinism and indeterminism. The discussion reflects ongoing debates in quantum mechanics without resolving the underlying issues.

Hybrid
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Hybrid said:

Well, in your second reference, equation 13.9 clearly gives probabilities for measurement results.
 
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stevendaryl said:
Well, in your second reference, equation 13.9 clearly gives probabilities for measurement results.

Thanks I picked up on that as well, however it's irritating to me that the author's didn't just come out and state if it's a realist interpretation or indeterminate. Although it does seem as though retro-causality would imply in-determinism.
 
The universe is deterministic according to the TSVF. Both the forwards and backwards evolving wave function evolve in accord with deterministic laws. Since both wave functions come together to constitute reality, reality will "seem" probabilistic if you don't know the backwards evolving wave function.
 
Hybrid said:
Thanks I picked up on that as well, however it's irritating to me that the author's didn't just come out and state if it's a realist interpretation or indeterminate. Although it does seem as though retro-causality would imply in-determinism.

As I understand it, the two-state vector formalism is Copenhagen. The formalism is not a new interpretation, but a re-packaging of Copenhagen to make certain calculations more intuitive. In particular, the formalism is not an interpretation because it does not aim to solve (or dissolve) the measurement problem, unlike real attempts at interpretation such as MWI, BM and Consistent Histories.
 
Agrippa said:
The universe is deterministic according to the TSVF. Both the forwards and backwards evolving wave function evolve in accord with deterministic laws. Since both wave functions come together to constitute reality, reality will "seem" probabilistic if you don't know the backwards evolving wave function.

Yes, and I'm aware of this as I've already looked it, although their view of determinism isn't so cut and dry, and leaves much to be desired. They used weak measurements to come to this conclusion which are questionable at best. (http://motls.blogspot.com/2012/09/pseudoscience-hiding-behind-weak.html)

Also I found this tidbit of information perusing around the internet interesting -

"Charles Bennett of IBM’s research laboratories in Yorktown Heights, New York, a specialist on quantum information theory, is not convinced. For a start, he sees the TSVF as only one way of looking at the results. “People in quantum foundations are often so wedded to their own interpretation or formalism that they say it is the only reasonable one, when in fact quantum mechanics admits multiple interpretations, which except for a few outliers are entirely equivalent to one another. The differences are aesthetic and philosophical, not scientific.”

Bennett believes that the findings can be interpreted without any apparent ‘backwards causation’, so that the authors are erecting a straw man. “To make their straw man seem stronger, they use language that in my opinion obscures the crucial difference between communication and correlation. They say that the initial weak measurement outcomes anticipate the experimenter's future choice but that doing so causes no violation of causality because the anticipation is encrypted.” But he thinks this is a bit like an experiment in quantum cryptography in which the sender sends the receiver the decryption key before sending (or even deciding on) the message, and then claims that the key is somehow an ‘anticipation’ of the message. With this in mind, it is not clear whether even an experiment will resolve the issue, since it would come down to a matter of how to interpret the results."


Point being that this is not actual determinism, it's still inherently indeterministic.

atyy said:
As I understand it, the two-state vector formalism is Copenhagen. The formalism is not a new interpretation, but a re-packaging of Copenhagen to make certain calculations more intuitive. In particular, the formalism is not an interpretation because it does not aim to solve (or dissolve) the measurement problem, unlike real attempts at interpretation such as MWI, BM and Consistent Histories.

Yes, I agree.

After evaluating all the interpretations of quantum mechanics indeterministic consistent histories makes the most sense of things.
 
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