Does the probability collapse theory of QM imply backward in time

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Discussion Overview

The discussion revolves around the implications of probability collapse theory in quantum mechanics (QM), particularly in relation to the thought experiment of Schrödinger's cat. Participants explore whether this theory suggests backward causation in time and how it relates to the certainty of events over time, especially in biological systems.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants propose that the cat's state remains uncertain until the box is opened, raising questions about when the cat's death and subsequent decomposition become certain.
  • Others argue that decomposition occurs in parallel with the cat's living state and becomes certain only upon measurement.
  • A participant references 'Quantum Enigma' to suggest that measurement creates a history of quantum systems, implying that macroscopic objects are also quantum systems despite decoherence.
  • One viewpoint suggests that in a time-symmetric interpretation, the cat's decomposition could interact with a beta decay event, leading to a backward transformation to a living state, although this is noted as a matter of personal preference.
  • Another participant challenges the relevance of biological complexity in the context of quantum events, suggesting that time may be suspended in the quantum system until measurement occurs.
  • There is a mention of decoherence complicating the scenario, with some asserting that backward causation is not necessary in most interpretations of QM.
  • Participants discuss the nature of quantum systems as potentially spatiotemporal objects, emphasizing the role of observation in determining a single history from superpositions.

Areas of Agreement / Disagreement

The discussion remains unresolved, with multiple competing views on whether probability collapse theory implies backward causation in time. Participants express differing interpretations of quantum mechanics and the implications for the Schrödinger's cat thought experiment.

Contextual Notes

Participants highlight limitations in understanding due to the complexity of biological systems, the role of decoherence, and the dependence on different interpretations of quantum mechanics.

fredt17
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In the thought experiment known as Schrödinger's cat a cat is placed in a sealed box, and its life or death is tied to an uncertain quantum event such as radioactive decay. If the radioactive particle decays, the cat dies. If not, nothing happens.

According to probability collapse QM, as I understand it, the cat is in an uncertain state until we open the box and collapse the probability wave created by the quantum event. But what if we wait ten days to open the box? Will we discover that, if the cat died, its body has decomposed for up to ten days?

But when did the ten days of decomposition occur (or become certain)? Does probability collapse theory claim that the death of the cat does not occur (or become certain) until we open the box and the decay too is uncertain even though the biological process will appear to have taken up to ten days?

Or does the probability collapse theory of QM imply a backward in time causation?
 
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fredt17 said:
Will we discover that, if the cat died, its body has decomposed for up to ten days?
Sure.
fredt17 said:
But when did the ten days of decomposition occur (or become certain)?
They occurred during the ten days - in parallel to the cat living there for 10 days. They became certain when you opened the box.

Anyway, living systems are too complex for such a superposition to happen. With some atoms, that scenario is possible.
fredt17 said:
Or does the probability collapse theory of QM imply a backward in time causation?
No.
 
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In 'Quantum Enigma' by Bruce Rosenblum and Fred Kuttner, they describe a measurement occurring. Using your example, ten days after setting up the experiment, upon measurement the appropriate history of the quantum systems is created. In principle, macroscopic objects (despite experiencing decoherence, which does -not- cause a definite reality to arise [only -apparent- collapse) are quantum systems also.
 
Depending on the interpretation. In time symmetric interpretation the answer is yes. The beta decay interact with a decomposed cat and that decomposed cat transforms continuously backward in time into a present alive cat. Of course in not being too precise but this is the general idea within this interpretation. The"no"answer is also possible and it is related to the more traditional collapse interpretation. I tend to like more the time symmetric interpretation because it preserves locality and determinism (but loses causality -as the cat"first decomposes and then goes back to life backward in time", you know what I mean-). Anyway is just a matter of taste.
 
the_pulp said:
Depending on the interpretation. In time symmetric interpretation the answer is yes. The beta decay interact with a decomposed cat and that decomposed cat transforms continuously backward in time into a present alive cat. Of course in not being too precise but this is the general idea within this interpretation. The"no"answer is also possible and it is related to the more traditional collapse interpretation. I tend to like more the time symmetric interpretation because it preserves locality and determinism (but loses causality -as the cat"first decomposes and then goes back to life backward in time", you know what I mean-). Anyway is just a matter of taste.
Sorry I wrote something wrong. What I tried to s say, generally speaking, is that we open the box and we interact with a decomposed dead cat which transforms continuously backward in time in a dead not decomposed cat which interacts with beta decay and transforms backward in time in a present alive carry. Sorry!
 
fredt17 said:
According to probability collapse QM, as I understand it, the cat is in an uncertain state until we open the box and collapse the probability wave created by the quantum event.
No, we are in an uncertain state. The cat is in a certain state.
 
:
Well, my understanding (like the pulp and StevieTNZ) is that the point of the Schrödinger's Cat experiment was to tie a micro event (such as the death of a cat) to a quantum event, and so the complexity of the biological event is irrelevant. Thus, the probability theory of QM does imply backward in time causation, or perhaps more accurately, that time is suspended in the quantum system until we measure the system. Have I got that right?
 
The backward-in-time interpretation for Schroedinger's Cat Paradox was detailed in a book by John Gribbin (Schroedinger's Kittens).
 
fredt17 said:
Well, my understanding (like the pulp and StevieTNZ) is that the point of the Schrödinger's Cat experiment was to tie a micro event (such as the death of a cat) to a quantum event, and so the complexity of the biological event is irrelevant.
It is still relevant. You get decoherence.
fredt17 said:
Thus, the probability theory of QM does imply backward in time causation, or perhaps more accurately, that time is suspended in the quantum system until we measure the system. Have I got that right?
The time-symmetric interpretation is one of many. You do not need backwards causation and most interpretations do not have that.
 
  • #10
Perhaps it's better to think of the quantum system as of an essentially spatiotemporal (existing in its space-time) object ?
It can be considered as a superposition of histories - until it (or our uncertainty?) is reduced by observation to one "actual" decoherent history.

Our problem seems to be the habit of imposing temporal evolution on Nature too much...
 
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  • #11
fredt17 said:
that time is suspended in the quantum system until we measure the system. Have I got that right?
That is right only in the interpretation of QM that stipulates that everything (not only time) is suspended until we measure the system.
 
  • #12
Demystifier said:
That is right only in the interpretation of QM that stipulates that everything (not only time) is suspended until we measure the system.
Which interpretation is this? Doesn't evolution within the isolated system continue until you open the box?
 

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