Information Theory and Entropy

Click For Summary

Discussion Overview

The discussion revolves around the relationship between entropy and information, exploring concepts such as the implications of entropy increase on information loss, the nature of wavefunction collapse, and the potential conservation of information in physical systems. The scope includes theoretical considerations and conceptual clarifications related to information theory and quantum mechanics.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that entropy and information are opposites, with increased information leading to decreased entropy due to fewer quantum states being consistent with the information available.
  • There is a suggestion that when particles interact, information may be lost due to the collapse of the wavefunction, resulting in only the total energy/momentum being known post-interaction.
  • One participant recalls a notion that information is never lost, referencing the concept of conservation of information.
  • Another participant mentions that while there is no established conservation of information, unitarity and CPT symmetry might imply some form of information conservation, as the past state must be contained in the present state.
  • Concerns are raised about wavefunction collapse not being a unitary transformation, suggesting that information may not be conserved in certain contexts.
  • A participant expresses uncertainty about the conservation of information, likening it to the non-conservation of energy and momentum in macroscopic systems.
  • References to the black hole information paradox are made, indicating a broader context for the discussion on information conservation.
  • One participant cites an article claiming that information cannot be copied or lost, introducing the concept of complementarity in relation to information conservation.

Areas of Agreement / Disagreement

Participants express differing views on whether information is conserved, with some suggesting it is lost during interactions while others argue for its conservation under certain conditions. The discussion remains unresolved regarding the implications of wavefunction collapse and the overall nature of information in quantum mechanics.

Contextual Notes

Limitations include the lack of consensus on the conservation of information and the dependence on interpretations of quantum mechanics, particularly regarding wavefunction collapse and its implications for information theory.

Arman777
Insights Author
Gold Member
Messages
2,163
Reaction score
191
1-Whats the relationship between entropy and İnformation ?
2-Can Entrophy always increases statement imply information lost ?
3-If it implies how its lost ?
 
Physics news on Phys.org
1. Entropy and information are basically opposites. Entropy tells you how many quantum states are consistent with the information you have. If you have more information about the state, then there are fewer states that match the description, so the entropy is less.
2. Yes.
3. When two particles interact, they trade some energy and momentum. The amount of energy/momentum transfer is in superposition. Somehow, the wavefunction collapses, and the amount of transfer takes on some random value. So, if we initially knew the energy/momentum of each particle before the interaction, afterwards we only know the total. So some information was lost. It's not clear how this wavefunction collapse occurs.
 
Last edited by a moderator:
  • Like
Likes   Reactions: Arman777
Khashishi said:
1. Entropy and information are basically opposites. Entropy tells you how many quantum states are consistent with the information you have. If you have more information about the state, then there are fewer states that match the description, so the entropy is less.
2. Yes.
3. When two particles interact, they trade some energy and momentum. The amount of energy/momentum transfer is in superposition. Somehow, the wavefunction collapses, and the amount of transfer takes on some random value. So, if we initially knew the energy/momentum of each particle before the interaction, afterwards we only know the total. So some information was lost. It's not clear how this wavefunction collapse occurs.

I understand thanks, "So some information was lost" , I remembered now that I heard İnformation never lost, never vanishes. Is this true ?
Like Conservation of Information ?
 
Last edited by a moderator:
I searched a bit and says there's no such conservation but From unitarity or cpt there could be
"CPT seems to imply it. You can reverse the system evolution by applying charge, parity and time conjugation, so the information about the past must be contained in the present state. That implies conservation of information by the evolution.

This may not be the answer you wanted, because it does not imply unitarity, but it is the only relationship between symmetry and information conservation that I can think of. Unitarity seems to be a very fundamental assumption though, and there is not much more fundamental mathematical structure you could use to argue about its necessity." (A.O.Tell,Physics Stack Exchange,https://physics.stackexchange.com/q...associated-to-the-conservation-of-information)
 
But, wavefunction collapse is not a unitary transformation.
 
Khashishi said:
But, wavefunction collapse is not a unitary transformation.
I don't know much things about wavefunction actually I am freshman at physics :)
So it doesn't conserved.
Like energy,momentum etc is even not conserved in macroscopic states,like galaxy clusters scale etc.So It make sense to me that its not conserved.Maybe we can say the information about the system is lost during the time.It never disappeares but it just turns something that we can't describe the full system after a period of time using previous information
 
Arman777 said:
I searched a bit and says there's no such conservation but From unitarity or cpt there could be
"CPT seems to imply it. You can reverse the system evolution by applying charge, parity and time conjugation, so the information about the past must be contained in the present state. That implies conservation of information by the evolution.
/QUOTE]

Sure, that's fine if it doesn't interact with anything.
 
  • #10
Makes sense...
 
  • #11
Well I read the article and says information is conserved.It can not be copied or lost.Which Complementarity came from that.
 

Similar threads

Undergrad Predetermination in quantum theory and information theory
  • · Replies 15 ·
Replies
15
Views
2K
Graduate Do entanglement networks encode a unique, local historical record?
  • · Replies 2 ·
Replies
2
Views
2K
Graduate Comparing Information Loss: Time Dilation vs. Decoherence
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Two Entropy scenarios on a system
  • · Replies 4 ·
Replies
4
Views
2K
Graduate QFT topics for entanglement entropy
  • · Replies 3 ·
Replies
3
Views
3K
High School Why Does Black Hole Entropy and Information Loss Matter?
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad Explaining atoms and bonding using entropy
  • · Replies 10 ·
Replies
10
Views
2K
Undergrad Intersection of Condensed Matter Theory + High Energy Physics
  • · Replies 0 ·
Replies
0
Views
1K
Undergrad Is Information Really Preserved in Quantum Systems?
  • · Replies 8 ·
Replies
8
Views
1K
High School Entropy & Information Content: Examining the Difference
  • · Replies 2 ·
Replies
2
Views
3K