Particle in superposition of energy eigenstates and conservation of energy.

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Discussion Overview

The discussion revolves around the implications of a particle being in a superposition of energy eigenstates, particularly in relation to the conservation of energy in quantum mechanics. Participants explore the nature of energy measurements, the role of operators, and the conditions under which superpositions can be prepared, with a focus on both theoretical and conceptual aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that the energy of a particle in superposition is inherently uncertain, with probabilities associated with measuring different energy eigenstates.
  • Others express a desire for quantum mechanics to provide definite answers regarding the total energy of a system.
  • A participant discusses the formulation of conservation laws in quantum mechanics through operator algebra and the implications of the Heisenberg picture.
  • Some argue that total energy is conserved even when a particle enters a superposition state, as energy must be accounted for in the overall system.
  • Questions arise about the possibility of preparing a particle in an energy superposition state without entanglement with another system.
  • Participants reference coherent states of the electromagnetic field and their relationship to energy eigenstates, noting that these states do not necessarily contain a definite number of photons.
  • There is a discussion about the implications of coherent states on energy conservation and the nature of interactions that involve energy exchange.
  • Some participants express skepticism about the assumption that the universe is a closed quantum system and the implications for energy conservation and correlations.
  • One participant points out that while a closed system must evolve unitarily, the creation of coherent superpositions of different energies may still be possible due to non-unitary evolution in various interpretations of quantum mechanics.

Areas of Agreement / Disagreement

Participants generally agree that energy is conserved in quantum mechanics, but multiple competing views remain regarding the nature of superpositions, the role of entanglement, and the implications of coherent states. The discussion remains unresolved on several theoretical points.

Contextual Notes

Participants note limitations in the assumptions made about closed systems and the nature of quantum measurements, as well as the complexities involved in defining energy in superposition states.

  • #31
K^2 said:
If you are talking about pure vs mixed states, that is exactly how you are defining your system. The distinction is only relevant statistically, and that implies an external system.
DrDu was talking about a CLASSICAL surrounding, while what you say above refers to a QUANTUM surrounding.

K^2 said:
Excited atom + ground state EM vacuum is still an eigen state of such a system.
It would be so if there was no interaction term in the Hamiltonian describing atom and EM field. But the interaction term is there, so what you say above is not correct.
 
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  • #32
The notion of a closed universe is quite interesting. Demystifier to expand on what you are saying, if energy eigenstates, so the different superpositions of a particle, must evolve into a coherent state, where does all this excess energy from these states go? Our universe,in accordance with things such as Pauli Exclusion can only have on outcome of a solution, and the physical existence of a particle in two different states seems impossible. Could it be that many worlds theory holds valid in that all these different energy eigenstates come together to form an infinite number of possibly universes, each branching from another, as a wave function collapses and the other superpositions become irrelevant to our world?
 

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