Find density matrice at zero and infinity temperature

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SUMMARY

The discussion focuses on calculating the density matrix for a two-state system at both zero and infinite temperatures. Key equations and matrices were provided, illustrating the relationship between the energy states \(E_1\) and \(E_2\) and the corresponding density matrix. The participants emphasized the significance of the parameter \(\beta\) in defining the finite temperature density matrix. The solutions presented demonstrate a clear understanding of the evolution of the density matrix under varying temperature conditions.

PREREQUISITES
  • Understanding of quantum mechanics principles, particularly two-state systems.
  • Familiarity with density matrices and their applications in statistical mechanics.
  • Knowledge of temperature limits in quantum systems, specifically zero and infinite temperatures.
  • Basic proficiency in mathematical notation used in physics, including the concept of \(\beta\).
NEXT STEPS
  • Study the derivation of the density matrix for quantum systems at finite temperatures.
  • Explore the implications of the canonical ensemble in statistical mechanics.
  • Learn about the role of the partition function in determining thermodynamic properties.
  • Investigate the effects of temperature on quantum state populations and coherence.
USEFUL FOR

Students and researchers in quantum mechanics, physicists working with statistical mechanics, and anyone interested in the behavior of two-state systems at varying temperatures.

romeo31415
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Homework Statement


upload_2015-1-16_9-52-47.png


Homework Equations



https://www.physicsforums.com/attachments/upload_2015-1-15_18-57-56-png.77691/
Density matrix for a 2 state system is:
https://www.physicsforums.com/attachments/upload_2015-1-15_19-1-30-png.77694/

The Attempt at a Solution


For a 2 finite state system, the matrice density at limit temperature is
https://www.physicsforums.com/attachments/upload_2015-1-15_18-59-39-png.77692/
https://www.physicsforums.com/attachments/upload_2015-1-15_18-59-56-png.77693/
[/B]

The Attempt at a Solution

 
Last edited by a moderator:
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You wrote the density matrix in terms of the energy and ##\beta##. What does the finite temperature density matrix in the problems tell you about ##E_1## and ##E_2##?

Could you give some details about how you reached the solutions you wrote?
 

Homework Equations



Density matrix for a 2 state system is:
upload_2015-1-16_23-10-22.png


The Attempt at a Solution


For a 2 finite state system, the matrice density at limit temperature is
upload_2015-1-16_23-11-35.png
[/B]
Evolution of the density matrix
upload_2015-1-16_23-12-31.png
 

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